Effects of membrane transport activity and cell metabolism on the unbound drug concentrations in the skeletal muscle and liver of drugs: A microdialysis study in rats

The unbound concentrations of 14 commercial drugs, including five non-efflux/uptake transporter substrates-Class I, five efflux transporter substrates-class II and four influx transporter substrates-Class III, were simultaneously measured in rat liver, muscle, and blood via microanalysis. Kpuu,liver and Kpuu,muscle were calculated to evaluate the membrane transport activity and cell metabolism on the unbound drug concentrations in the skeletal muscle and liver. For Class I compounds, represented by antipyrine, unbound concentrations among liver, muscle and blood are symmetrically distributed when compound hepatic clearance is low. And when compound hepatic clearance is high, unbound concentrations among liver, muscle and blood are asymmetrically distributed, such as Propranolol. For Class II and III compounds, overall, the unbound concentrations among liver, muscle, and blood are asymmetrically distributed due to a combination of hepatic metabolism and efflux and/or influx transporter activity.

Applications of shun shell column and nanocomposite sorbent for analysis of eleven anti-hypertensive in human plasma

High-performance liquid chromatography (HPLC) and solid phase micro membrane tip extraction (SPMMTE) methods are developed for the simultaneous analysis of eleven cardiovascular drugs in human plasma. Iron nanoparticles were obtained by the green method, characterized by XRD, FT-IR, TEM, and EDS and utilized in SPMMTE for sample preparation. The mobile phase used was ammonium acetate buffer-methanol-acetonitrile (65:18:17) with a 1.0 mL/min flow rate at 260 nm detection. Column used was Sunshell C₁₈ 150 × 4.6 mm, 2.6 µm. The values of k, α, and Rs were ranged from 040 to109.22, 1.20 to 2.67 and 1.0 to 26.18. SPMMTE and HPLC methods were fast, reproducible, precise, robust, economic and rugged for analysis of methyldopa, hydrochlorothiazide, prazosin hydrochloride, furosemide, labetalol, propranolol, valsartan, losartan potassium, diltiazem, irbesartan and spironolactone in human plasma. The recoveries (%) of methyldopa, hydrochlorothiazide, prazosin hydrochloride, furosemide, labetalol, propranolol, valsartan, losartan potassium, diltiazem, irbesartan, and spironolactone were 91.0, 85.2, 92.3, 90.4, 90.1, 85.6, 86.6, 86.2, 85.1, 86.6, and 85.7, respectively. These results showed that SPMMTE and HPLC methods can be applied to test the described drugs in several matrices.

Double-wavelength overlapping resonance Rayleigh scattering technique for the simultaneous quantitative analysis of three β-adrenergic blockade

Four simple and accurate spectrophotometric methods were proposed for the simultaneous determination of three β-adrenergic blockade, e.g. atenolol, metoprolol and propranolol. The methods were based on the reaction of the three drugs with erythrosine B (EB) in a Britton-Robinson buffer solution at pH4.6. EB could combine with the drugs to form three ion-association complexes, which resulted in the resonance Rayleigh scattering (RRS) intensity that is enhanced significantly with new RRS peaks that appeared at 337 nm and 370 nm, respectively. In addition, the fluorescence intensity of EB was also quenched. The enhanced scattering intensities of the two peaks and the fluorescence quenched intensity of EB were proportional to the concentrations of the drugs, respectively. What is more, the RRS intensity overlapped with the double-wavelength of 337 nm and 370 nm (so short for DW-RRS) was also proportional to the drugs concentrations. So, a new method with highly sensitive for simultaneous determination of three bisoprolol drugs was established. Finally, the optimum reaction conditions, influencing factors and spectral enhanced mechanism were investigated. The new DW-RRS method has been applied to simultaneously detect the three β-blockers in fresh serum with satisfactory results.

Antihypertensive effects, plasma levels and beta-adrenergi blocking activity of racemic and dextrorotatory propranolol in man

In hypertensive patients, whose blood pressure was decreased by racemic propranolol, the dextrorotatory isomer had no antihypertensive effect. The differences in antihypertensive activity of racemic and dextrorotatory propranolol cannot be explained by different plasma levels. The data indicate that the hypotensive effect of propranolol is due to beta-receptor blockade.

A study of the relationship between serum bile acids and propranolol pharmacokinetics and pharmacodynamics in patients with liver cirrhosis and in healthy controls

The main objectives of the study were to determine the exposure and bioavailability of oral propranolol and to investigate their associations with serum bile acid concentration in patients with liver cirrhosis and in healthy controls. A further objective was to study the pharmacodynamics of propranolol. An open-label crossover study was performed to determine the pharmacokinetics and pharmacodynamics of propranolol after oral (40 mg) and intravenous (1 mg) administration as well as the concentration of total and individual fasting serum bile acids in 15 patients with liver cirrhosis and 5 healthy controls. After intravenous propranolol, patients showed a 1.8-fold increase in the area under the plasma concentration-time curve (AUC_0–∞), a 1.8-fold increase in volume of distribution and a 3-fold increase in the elimination half-life (mean ± SEM: 641±100 vs. 205±43 minutes) compared to controls. After oral application, AUC_0–∞ and elimination half-life of propranolol were increased 6- and 4-fold, respectively, and bioavailability 3-fold (83±8 vs. 27±9.2%). Maximal effects on blood pressure and heart rate occurred during the first 4 and first 2 hours, respectively, after intravenous and oral application in both patients and controls. Total serum bile acid concentrations were higher in patients than controls (42±11 vs. 2.7±0.3 µmol/L) and were linearly correlated with the serum chenodeoxycholic acid concentration. There was a linear correlation between the SBA concentration and propranolol oral AUC_0–∞ in subjects not receiving interacting drugs (r² = 0.73, n = 18). The bioavailability of and exposure to oral propranolol are increased in patients with cirrhosis. Fasting serum bile acid concentration may be helpful in predicting the exposure to oral propranolol in these patients.

In vivo and in vitro liver and gill EROD activity in rainbow trout (Oncorhynchus mykiss) exposed to the beta-blocker propranolol

The conservation of common physiological systems across vertebrate classes suggests the potential for certain pharmaceuticals, which have been detected in surface waters, to produce biological effects in nontarget vertebrates such as fish. However, previous studies assessing the effects of such compounds in fish have not taken into account the potential for metabolism and elimination. This study aimed to assess if propranolol, a β-adrenergic receptor antagonist or β-blocker, could modulate EROD activity (indicative of CYP1A activity) in rainbow trout (Oncorhynchus mykiss) gills and liver. For this, an in vivo time course exposure with 1 mg/L was conducted. Additionally, using measured in vivo plasma concentrations, an in vitro exposure at human therapeutic levels was undertaken. This allowed comparison of in vitro and in vivo rates of EROD activity, thus investigating the applicability of cell preparations as surrogates for whole animal enzyme activity analysis. In vitro exposure of suspended liver and gill cells at concentrations similar to in vivo levels resulted in EROD activity in both tissues, but with significantly higher rates (up to six times in vivo levels). These results show that propranolol exposure elevated EROD activity in the liver and gill of rainbow trout, and that this is demonstrable both in vivo (albeit nonsignificantly in the liver) and in vitro, thus supporting the use of the latter as a surrogate of the former. These data also provide an insight into the potential role of the gill as a site of metabolism of pharmaceuticals in trout, suggesting that propranolol (and feasibly other pharmaceuticals) may undergo "first pass" metabolism in this organ.

[Rapid determination of propranolol enantiomers in rat plasma by column-switching-high performance liquid chromatography]

A high performance liquid chromatographic (HPLC) method with column-switching was developed and validated for rapid determination of two propranolol enantiomers in rat plasma. The column of restricted-access media was used as a pre-treatment column and a Chiralcel OD-RH was used as analytical column. The plasma samples were injected directly into the pretreatment column to remove plasma protein and endogenous constituents as well as to retent the propranolol enantiomers in the column using the mobile phase of borate buffer (pH 8.5)-methanol (95:5, v/v) at the flow rate of 1.0 mL/min. Then the propranolol enantiomers were transferred to the Chiralcel OD-RH column using the mobile phase of isopropanol-ethanol-0.2 mmol/L borate buffer (pH 8.5) (30: 30: 40, v/v/v) at a flow rate of 0.8 mL/min by column-switching technology. The column-switching time was 3.0 min, the used wavelength was 293 nm and the column temperature was set at 25 degrees C. The calibration curve showed excellent linear relationship (r = 0.999 5) in the concentration range from 25 mg/L to 500 mg/L for propranolol enantiomers in plasma. The intra-day and inter-day assay precisions and accuracies were well and the relative standard deviations (RSDs) were less than 5%. The average recoveries (n = 6) of the two enantiomers at 3 spiked levels were from 97.89% to 101.56%. All the values of the method validation were within the generally accepted criteria for biological sample analysis. The results show that the method is convenient, quick, sensitive and accurate. The method was successfully applied in the determination of propranolol enantiomers in rat blood pharmacokinetics study.

Chronic effects assessment and plasma concentrations of the beta-blocker propranolol in fathead minnows (Pimephales promelas)

The presence of many human pharmaceuticals in the aquatic environment is now a worldwide concern, yet little is known of the chronic effects that these bioactive substances may be having on aquatic organisms. Propranolol, a non-specific beta adrenoreceptor blocker (beta-blocker), is used to treat high blood pressure and heart disease in humans. Propranolol has been found in surface waters worldwide at concentrations ranging from 12 to 590ng/L. To test the potential for ecologically relevant effects in fish in receiving waters, short-term (21 days) adult reproduction studies were conducted, in which fathead minnows were exposed to nominal concentrations of propranolol hydrochloride [CAS number 318-98-9] ranging from 0.001 to 10mg/L (measured concentrations typically from 78 to 130%). Exposure of fish to 3.4mg/L (measured) over 3 days caused 100% mortality or severe toxicity requiring euthanasia. The most sensitive endpoints from the studies were a decrease in hatchability (with regard to the number of days to hatch) and a concentration-related increase in female gonadal somatic index (GSI), giving LOEC(hatchability) and LOEC(female GSI) values of 0.1mg/L. Concentration-related decreases in weights of male fish were also observed, with LOEC(male wet weight value) of 1.0mg/L, and the LOEC(reproduction) value was 1.0mg/L. Collectively, these data do not suggest that propranolol was acting as a reproductive toxin. Plasma concentrations of propranolol in male fish exposed to nominal concentrations of 0.1 and 1.0mg/L were 0.34 and 15.00mg/L, respectively, which constitutes 436 and 1546% of measured water concentrations. These compare with predicted concentrations of 0.07 and 0.84mg/L, and thus to a degree support the use of partition coefficient models for predicting concentrations in plasma in fish. In addition, propranolol plasma concentrations in fish exposed to water concentrations of 0.1 and 1.0mg/L were greater than the human therapeutic plasma concentration and hence these data very strongly support the fish plasma model proposed by Huggett et al. [Huggett, D.B., Cook, J.C., Ericson, J.F., Williams, R.T., 2003a. A theoretical model for utilizing mammalian pharmacology and safety data to prioritize potential impacts of human pharmaceuticals to fish. Hum. Ecol. Risk Assess. 9, 1789-1799].

Uptake of propranolol, a cardiovascular pharmaceutical, from water into fish plasma and its effects on growth and organ biometry

Pharmaceuticals in the environment (PIE) are of importance since these compounds are designed to affect biological receptors/enzymes that are often conserved across vertebrate families. Across-species extrapolation of these therapeutic targets suggests potential for impacting amphibia and fish in the aquatic environment. Due to the scarcity of relevant ecotoxicological data, the long-tem impact of PIE remains a research question. Efficient use of mammalian data has been proposed to better understand and predict the potential for a given pharmaceutical to impact the environment. Using a model cardiovascular pharmaceutical (propranolol, a non-specific beta(1)/beta(2)-adrenergic antagonist), the hypothesis that mammalian data can be used to predict toxicity in fish was tested. Rainbow trout (Oncorhynchus mykiss (Walbaum)) have beta-adrenergic signalling mechanisms analogous to human cardiovascular receptors that respond to pharmacological doses of agonists and antagonists. Trout absorbed propranolol from water such that after 40 days of exposure, the linear relationship was [plasma] - 0.59[water] (n - 31, r - 0.96). Growth rate was affected only at very high aqueous concentrations (10-day (growth)NOEC - 1.0 and (growth)LOEC - 10 mg/l). Growth recovered with time (40-day (growth)NOEC - 10 mg/l), suggesting possible adaptation to the pharmaceutical, although the internal plasma concentration in trout exposed to 10mg propranolol/l of water was higher than the mammalian therapeutic plasma concentration. Additional endpoints suggested subtle changes of liver and heart size at much lower concentrations may have occurred, although these were not concentration-related. There was, however, a dose-dependent effect upon overall body condition. The trout plasma concentrations at these effective aqueous concentrations fell within the range of mammalian effective plasma concentrations, supporting the potential for developing 'read-across' from mammalian pharmacology safety data to fish ecotoxicology. Despite these effects at relatively high concentrations, propranolol is not expected to pose a risk to fish at the concentrations considered to be present in the aquatic environment.

Stress, catecholamines and beta-blockade

In order to investigate the effects of beta-blockade on haemodynamic response to stress, 2 groups of volunteers received either propranolol or mepindolol sulphate under basal conditions and under the stress of mental arithmetic. In control conditions, increases occurred in heart rate (HR), cardiac output (CO) and systolic and diastolic blood pressure in response to calculation stress. Stress-induced increases in HR and CO were significantly reduced by propranolol. Systolic blood pressure during calculation stress under propranolol was slightly less than in control conditions. However, diastolic blood pressure under stress was higher with propranolol than in the control study. Mepindolol sulphate also reduced HR and CO under calculation stress but it produced no significant change in diastolic pressure. A significant increase in plasma adrenaline occurred under stress. The level was not altered by propranolol but was reduced to less than 50% of the untreated stress value by mepindolol. Since beta-blocking agents suppress an increase in heart rate in stressful situations but either fail to prevent or even potentiate increased diastolic pressure, their use in patients without hypertension should be reserved for those showing pathological stress reactions. They do not appear to be indicated for the management of stressful situations in general.

Effects of labetalol and propranolol on the peripheral circulation in hypertensive patients

Eleven patients with essential hypertension participated in a double-blind cross-over comparison of labetalol (L) and propranolol (P). Each drug was given for 5--8 weeks. The dose reducing the supine diastolic blood pressure when given b.d. to or below 90 mm Hg was titrated out. At the end of each period, isometric exercise (sustained handgrip) and calf plethysmography were performed. L (mean daily dose 636 mg) was slightly more effective in lowering supine and standing blood pressure than P (mean dose 276 mg). There was no significant difference between the drugs in their effect on the blood-pressure response to handgrip. However, compared with no treatment, L attenuated the blood-pressure rise at near-maximal handgrip; this has not been reported with other beta-blockers. Resting vascular resistance and basal vascular tone were significantly lower (20%, p less than 0.05) during treatment with labetalol than when the patients were taking propranolol. - The differences may be explained by the alpha-receptorblocking action of labetalol.

In vitro and in vivo evaluation of locust bean gum and chitosan combination as a carrier for buccal drug delivery

The object of the study was to evaluate locust bean gum and chitosan in ratios of 2:3; 3:2 and 4:1 (F1, F2 and F3) as a mucoadhesive component in buccal tablets and to compare the bioavailability of a propranolol hydrochloride buccal tablet with the oral tablet in healthy human volunteers. Propranolol hydrochloride buccal tablets containing various weight ratios of locust bean gum and chitosan were prepared and coated with 5% w/v ethyl cellulose on one face, and oral tablets containing 10 mg propranolol hydrochloride alone were formulated using a direct compression technique. The strength of mucoadhesion of the tablets was quantified based on the tensile force required to break the adhesive bond between a model membrane (porcine buccal mucosa) and the test polymer. The forces of detachment for the mucoadhesive buccal tablets were 14.61 +/- 0.14, 13.21 +/- 0.13 and 11.71 +/- 0.12. An in vitro study was carried out in pH 6.8 phosphate buffer and the cumulative percentage release of propranolol measured at 10 min intervals for 600 min was found to be 98.31 +/- 0.10, 92.24 +/- 0.41 and 90.18 +/- 0.76 respectively. A bioavailability study was conducted with the prepared formulation in 16 healthy human volunteers to determine the plasma concentration of propranolol at 0, 1, 2, 3, 4, 6, 8, 10 and 12 h. The bioavailability (AUC(0-t*) ng x h/ml) of the buccal propranolol hydrochloride tablets (F1, F2 and F3) and oral tablet (F4) was found to be 2244.18 +/- 210, 3580.69 +/- 460, 3889.19 +/- 290 and 1732 +/- 96 ng x hr/ml respectively. The study indicates that locust bean gum and chitosan in a weight ratio of 2:3 (F1) not only releases the drug unidirectionally from the dosage form, but also gives buccal tablets which are sufficiently mucoadhesive for clinical applications.

On-line coupling of sequential injection extraction with restricted-access materials and post-column derivatization for sample clean-up and determination of propranolol in human plasma

The presented paper deals with a new methodology for direct determination of propranolol in human plasma. The methodology described is based on sequential injection analysis technique (SIA) coupled with solid phase extraction (SPE) column based on restricted access materials (RAM). Special RAM column containing 30 microm polymeric material-N-vinylacetamide copolymer was integrated into the sequential injection manifold. SIA-RAM system was used for selective retention of propranolol, while the plasma matrix components were eluted with two weak organic solutions to waste. Due to the acid-basic and polarity properties of propranolol molecule and principles of reversed-phase chromatography, it was possible to retain propranolol on the N-vinylacetamide copolymer sorbent (Shodex MSpak PK-2A 30 microm (2 mm x 10 mm)). Centrifuged plasma samples were aspirated into the system and loaded onto the column using acetonitrile-water (5:95, v/v), pH 11.00, adjusted by triethylamine. The analyte was retained on the column while proteins contained in the sample were removed to waste. Interfering endogenous substances complicating detection were washed out by acetonitrile-water (15:85), pH 11.00 in the next step. The extracted analyte was eluted by means of tetrahydrofuran-water (25:75), pH 11.00 to the fluorescence detector (emission filter 385 nm). The whole procedure comprising sample pre-treatment, analyte detection and column reconditioning took about 15 min. The recoveries of propranolol from undiluted plasma were in the range 96.2-97.8% for three concentration levels of analyte. The proposed SIA-RAM method has been applied for direct determination of propranolol in human plasma.

Analysis of hepatic metabolism affecting pharmacokinetics of propranolol in humans

We examined the metabolic kinetics of propranolol, constructed from saturable and non-saturable components, using liver microsomes. The metabolic activity in rat microsomes was much higher than that in human microsomes within the clinically observed plasma range. Using the physiologically based pharmacokinetic (PBPK) model incorporating the obtained metabolic parameters, the plasma kinetics of propranolol was well correlated with reported values, and then used to analyze the effect of hepatic first-pass metabolism on propranolol plasma pharmacokinetics in clinical doses. The simulated plasma concentrations and AUC values of propranolol increased proportionally to its dose; these levels were almost equivalent to intrinsic clearance (CLint1), presumed to be non-saturable. When Michaelis-Menten parameters were decreased to one twentieth, plasma concentrations slightly increased after 160 mg dosing. A similar result was obtained with steady-state plasma levels after repeated administration. On the other hand, the first-order absorption rate constant of propranolol did not affect AUC values. The dose-normalized AUC value started to increase about 10(3)mg dosing. When the dose exceed 10(6)mg dose, the CLint1 component hardly contributed to propranolol pharmacokinetics. Accordingly, under the conditions of the PBPK model, propranolol pharmacokinetics was considered to be dose-independent within the clinical dose range.

Propranolol plasma monitoring in children submitted to surgery of tetralogy of Fallot by a micromethod using high performance liquid chromatography

OBJECTIVE

To evaluate the analytical micromethod using liquid chromatography for the quantification of propranolol in children submitted to surgery of tetralogy of Fallot (TLF).

METHODS

Only 0.2 mL of plasma is required for the assay. Peaks eluted at 8.4 (Propranolol) and 17.5 min (verapamil, internal standard) from a C18 column, with a mobile phase 0.1 M acetate buffer, pH 5.0, and acetonitrile (60:40, v/v) at flow rate 0.7 mL/min, detected at 290 nm (excitation) and 358 nm (emission). Surgery was started 776 min of drug administration (8.7 mg, mean); seven blood samples were collected from six patients (4M/2F; 2.1 yrs;11.5 kg; 0.80 m; 18.9 kg/m(2)).

RESULTS

Confidence limits of the method showed high selectivity and recovery, sensitivity of 0.02ng/mL, good linearity (0.05-1000 ng/mL), precision of 8.6% and accuracy of 3.1%. The mean duration of surgery was 283.2 min, with the patients remaining under cardiopulmonary bypass (CPB) for 114 min. A declining curve of propranolol plasma concentration was obtained after the last dose in the night that preceded the day of surgery. Plasma concentration also was normalized with hematocrit due to the hemodilution caused by the CPB procedure. On the other hand a decrease on drug plasma concentration was obtained between periods, the beginning of surgery to the postoperative day 2 (7.09 ng/mL and 0.05 ng/mL, p<0.05 respectively) and from the end of CPB to the postoperative day 2 (2.79 ng/mL e 0.05 ng/mL, p<0.05).

CONCLUSION

Propranolol monitoring of plasma concentrations of children (TLF) normalized after the last preoperative dose revealed a decline from the beginning of surgery to the second postoperative day, suggesting that, once redistribution was restored, propranolol washout was complete.

Simultaneous determination of ten antiarrhythic drugs and a metabolite in human plasma by liquid chromatography—tandem mass spectrometry

A simple, accurate and selective LC-MS/MS method was developed and validated for simultaneous quantification of ten antiarrhythic drugs (diltiazem, amiodarone, mexiletine, propranolol, sotalol, verapamil, bisoprolol, metoprolol, atenolol, carvedilol) and a metabolite (norverapamil) in human plasma. Plasma samples were simply pretreated with acetonitrile for deproteinization. Chromatographic separation was performed on a Capcell C(18) column (50mmx2.0mm, 5microm) using a gradient mixture of acetonitrile and water (both containing 0.02% formic acid) as a mobile phase at flow rate of 0.3ml/min. The analytes were protonated in the positive electrospray ionization (ESI) interface and detected in multiple reaction monitoring (MRM) mode. Calibration curves were linear over wide ranges from sub- to over-therapeutic concentration in plasma for all analytes. Intra- and inter-batch precision of analysis was <12.0%, accuracy ranged from 90% to 110%, average recovery from 85.0% to 99.7%. The validated method was successfully applied to therapeutic drug monitoring (TDM) of antiarrhythic drugs in routine clinical practice.

Elastic liposomes mediated transdermal delivery of an anti-hypertensive agent: propranolol hydrochloride

One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present investigation ultradeformable lipid vesicles, that is, elastic liposomes were prepared incorporating propranolol hydrochloride for enhanced transdermal delivery. Elastic liposomes bearing propranolol hydrochloride were prepared by conventional rotary evaporation method and characterized for various parameters including vesicles shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, turbidity, and in vitro drug release. In vitro flux, enhancement ratio (ER), and release pattern of propranolol hydrochloride were calculated for transdermal delivery. In vivo study conducted on male albino rats (Sprague Dawley) was also taken as a measure of performance of elastic liposomal, liposomal, and plain drug solution. The better permeation through the skin was confirmed by confocal laser scanning microscopy (CLSM). Results indicate that the elastic liposomal formulation for transdermal delivery of propranolol hydrochloride provides better transdermal flux, higher entrapment efficiency, ability as a self-penetration enhancer and effectiveness for transdermal delivery as compared to liposomes.

Pravastatin reverses the down-regulating effect of inflammation on β-Adrenergic receptors: A disease–drug interaction between inflammation, pravastatin, and propranolol

Inflammatory conditions reduce the potency to prolong the PR interval of certain cardiovascular drugs including propranolol, sotalol, and verapamil in rats and humans despite elevated plasma drug concentrations. We tested whether pravastatin restores altered action and disposition of propranolol as well as inflammatory mediators concentrations in the Pre-Adjuvant Arthritis (Pre-AA) Sprague-Dawley rat model. Rats [Healthy/Placebo, Arthritis/Placebo, Healthy/Statin, and Arthritis/Statin groups (n=14-16/group)] received Mycobacterium butyricum on day 0 followed by 6 mg/kg pravastatin or placebo twice daily during days 4-8. PR-interval response to 25 mg/kg oral propranolol was measured on days 0, 4 and 8. On day 8, blood samples were collected for interferon-gamma, interleukin-10, C-reactive protein, and nitrite measurements. Propranolol enantiomer pharmacokinetics were delineated using another 4 groups (healthy n=5, Pre-AA n=9) on day 8. Pre-AA significantly reduced propranolol response despite a 10-fold increase in concentrations. Pravastatin restored the response but not the drug concentrations. Area under the % effect-time curve (% min) was 714+/-214 in Healthy/Placebo, 256+/-249 in Arthritis/Placebo, 1534+/-367 in Healthy/Statin, and 1713+/-393 in Arthritis/Statin. While pravastatin reduced elevated serum interferon-gamma concentration in the Pre-AA model, it did not influence other biomarkers. Pravastatin restores response to propranolol in inflamed rat but has no effect on the elevated propranolol concentrations. This was associated with lower serum interferon-gamma concentrations.

Comparative effects of ivabradine, a selective heart rate-lowering agent, and propranolol on systemic and cardiac haemodynamics at rest and during exercise

AIM

To compare in humans the effects of ivabradine and propranolol on cardiac and systemic haemodynamics at rest, during tilt and exercise.

METHODS

Nine healthy volunteers randomly received single oral doses of ivabradine (Iva, 30 mg), propranolol (Propra, 40 mg) or placebo (Plac) during a double-blind cross-over study. Doses were selected to be equipotent in heart rate (HR) reduction. HR, systolic and diastolic blood pressure (SBP, DBP), cardiac index (CI, bioimpedance), rate pressure product (RPP), plasma epinephrine (E) and norepinephrine (NE), were measured at rest at baseline, before and after two tilt and exercise tests, started 2 and 5 h after drug intake. Heart rate variability (low to high frequency ratio LF/HF) was evaluated at rest and at 5 th minute of tilt.

RESULTS

At rest, HR and RPP decreased similarly with Iva and Propra (both P < 0.01). During tilt, HR increased less with Iva than Propra (P < 0.01), LF/HF decreased after Iva (P < 0.03), SBP and mean blood pressure decreased after Propra (both P < 0.01), RPP decreased similarly after Iva and Propra (both P < 0.01) and CI decreased to a greater extent with Propra than with Iva or Plac (both P < 0.04). During exercise, Iva and Propra similarly decreased HR (both P < 0.01) and RPP (P < 0.01).

CONCLUSIONS

These results demonstrate that for a similar decrease in HR at rest and during sympathetic stimulation, acute administration of ivabradine, a selective heart rate-lowering agent, decreased myocardial oxygen demand to the same extent as a reference beta-blocker, propranolol, but without evidence of depressant effect on cardiac function.

H3 Propranolol serum levels following lidocaine administration in rats with CCL4 — induced liver damage

Liver disease alters the pharmacokinetic and pharmacodynamic properties of hepatically eliminated drugs. The main factors influenced are plasma albumin levels, enzyme balance (induction & inhibition) and drug binding to tissue proteins. The influence of lidocaine on serum, heart and liver propranolol levels in Wistar rats after liver injury induced by carbon tetrachloride CCl4 0.4 ml/kg x 2/wkl, was investigated. 40 male Wistar rats were divided into four groups (I, II, III, IV; n=10), Group I animals received only propranolol (labelled + cold substance) 40 mg/kg/12 h p.o., group II propranolol plus lidocaine in a single dose of 4mg/kg s.c., group III was treated with CCl4 for 6 weeks and received propranolol x2 at the same dosage as group I, while group VI was treated with CCl4 and the same drug dosage as group II. The simultaneous administration of H3-propranolol and lidocaine increased propranolol levels in the serum and tissues. The liver in damaged animals showed an increase of propranolol level under lidocaine co-administration, probably due to CCl4 induced liver enzyme activity, resulting in a rapid propranolol metabolism or to competition between both drug protein binding sites. The increased propranolol levels in the heart after lidocaine administration were probably due to attributed to its high affinity for heart tissue. Consequently, as regards the therapeutic approach for patients with liver disease receiving propranolol their propranolol dosage should be reduced when lidocaine is co-administered.

Supercritical Fluid Chromatography−Tandem Mass Spectrometry for the Enantioselective Determination of Propranolol and Pindolol in Mouse Blood by Serial Sampling

Packed-column supercritical fluid chromatography (pSFC) coupled to an atmospheric pressure chemical ionization (APCI) source and a tandem mass spectrometer (MS/MS) with minimum sample pretreatment was explored for the rapid and enantioselective determination of (R,S)-propranolol in mouse blood. Serial bleeding of mice is advantageous for the reduction of animal usage, dosing errors, and animal-to-animal variation. The effects of the eluent flow rate and composition as well as the nebulizer temperatures on the ionization efficiency of racemic propranolol and pindolol as model compounds in the positive ion mode under pSFC conditions were studied. The fundamental parameters on the proposed hyphenated system such as matrix ionization suppression and chromatographic performances were investigated in improving sensitivity and enantiomeric separation for the detection of the analytes. The proposed chiral pSFC-APCI/MS/MS approach requiring approximately 3 min/sample for the determination of (R,S)-propranolol at a low nanogram per milliliter region was partially validated with respect to specificity, linearity, reproducibility, and accuracy and was applied to support a pharmacokinetic study.

A rabbit model for sublingual drug delivery: Comparison with human pharmacokinetic studies of propranolol, verapamil and captopril

A rabbit model for investigating sublingual drug absorption was established yielding results consistent with clinical data reported in the literature. Using propranolol as a model compound the effect of formulation and dosing variables was explored as a means to characterize the limiting parameters of this model. In addition, verapamil and captopril were selected as reference compounds to compare this model to sublingual absorption in humans. Rabbits were dosed sublingually and systemic absorption was measured over time. Sublingual absorption of propranolol was dependent on dosing solution pH and volume. Intra-oral spray device did not affect the overall exposure compared to instillation using a syringe. Despite species and dosing regimen differences the relative bioavailabilities of propranolol and verapamil were very similar in rabbits and humans. In contrast, captopril absorption from the sublingual cavity of rabbits was low and did not agree with that observed in man. Here we report a sublingual rabbit model of drug delivery and its potential utility in preclinical development of intra-oral dosage forms.

FIRST-PASS HYDROLYSIS OF A PROPRANOLOL ESTER DERIVATIVE IN RAT SMALL INTESTINE

To evaluate the first-pass hydrolysis of O-isovaleryl-propranolol (isovaleryl-PL), which was used as a model ester-compound, rat intestinal jejunum and blood vessels were perfused simultaneously. The membrane permeability of isovaleryl-PL was greater than that of PL because it was more lipophilic. Isovaleryl-PL was almost completely hydrolyzed to PL and isovaleric acid (IVA) in epithelial cells at a rate limited by its uptake. Based on pH partitioning, PL and IVA were transported into both vascular (pH 7.4) and luminal sides (pH 6.5). Therefore, when isovaleryl-PL was perfused into the jejunal lumen, more than 90% permeated into the blood vessel as PL. In addition, PL appeared in the lumen at a rate 6-fold greater than that in blood vessels. When isovaleryl-PL was perfused, its disappearance (50.5+/-1.95 nmol/min) was the sum of the absorption and secretion rates of PL. In contrast, IVA was transported into blood vessels rather than the jejunal lumen. In addition, the calculated degradation clearance from in vitro hydrolysis (Km 13.7+/-1.71 microM, Vmax 29.1+/-3.81 nmol/min/mg protein) was 3.42 ml/min/10 cm jejunum, which was 24-fold greater than the observed degradation clearance (CLdeg) (0.14+/-0.02 ml/min/10 cm jejunum). These findings indicate that in addition to the liver, the intestine markedly contributes to first-pass hydrolysis.

Application of substrate depletion assay for early prediction of nonlinear pharmacokinetics in drug discovery: Assessment of nonlinearity of metoprolol, timolol, and propranolol

The purpose of this study was to investigate the advantages of the substrate depletion assay for evaluating linearity of pharmacokinetics compared with the metabolite formation assay. For propranolol, metoprolol, and nisoldipine with multiple and/or sequential metabolisms, the Michaelis constant (Km) and maximum metabolic intrinsic clearance obtained from the depletion assay using rat and human liver microsomes showed a good correlation with relevant parameters with the formation assay. In vitro kinetics and in vivo pharmacokinetic profiles after oral administration of timolol, metoprolol, and propranolol, were investigated in rats using the depletion assay. The same rank order was found between nonlinearities based on dose-normalized areas under the plasma concentration curve (AUC/Dose) and Km values. Using the kinetic parameters of these compounds, AUC was predicted based on a physiological based pharmacokinetic model incorporated saturable metabolism. The AUCs predicted for propranolol and metoprolol had a good relationship with those observed in the in vivo studies, implying that the depletion assay could be useful for assessing linearity of pharmacokinetics.

Polymorphic variants of the beta2-adrenergic receptor (ADRB2) gene and ADRB2-related propanolol-induced dyslipidemia in the Colombian population

Different polymorphisms of the ADRB2 gene encoding the beta-adrenergic receptor (ADRB2) are associated with changes in a variety of responses of the sympathetic nervous system (SNS). In this study, we have investigated the distribution of frequencies of ADRB2-related allelic variants (Arg16Gly, Gln27Glu, Thr164Ile) in the Colombian population, as well as the influence of the Gln27Glu polymorphism as a risk factor for the development of dyslipidemia following propranolol administration. Genotyping was performed in unrelated Colombian volunteers, using PCR-RFLP methods. To examine the association between the Gln27Glu polymorphism of the ADRB2 gene and dyslipidemia induced by propranolol, we recruited 19 healthy individuals who were homozygous for either the Gln27 (wild-type, N = 11) or the Glu27 (homozygous mutant, N = 8) genotype. Electrocardiography (ECG), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), serum lipid levels (T-CHO, HDL-CHO, TG), and fibrinogen were determined before and after propranolol administration. The distribution of genotypes was as follows: Arg16Arg 46%, Arg16Gly 47.4%, Gly16Gly 6.6%, Gln27Gln 44.7%, Gln27Glu 48.2%, and Glu27Glu 7.1%, with allelic frequencies of 69.7% for Arg16, 30.3% for Gly16, 68.8% for Gln27, and 31.2% for Glu27. The Thr164Ile polymorphism was found only in one subject, who was heterozygous for the isoleucine variant. Significant changes in physiological parameters (HR, SBP, DBP) have been found in association with ADRB2 variants in both native and mutant subgroups after propranolol intake. HDL-CHO levels diminished (p = 0.005) in native homozygous individuals (Gln27Gln), whereas TG levels were found increased (p = 0.012) in the mutant homozygous individuals (Glu27Glu). T-CHO levels and serum fibrinogen levels remained unaltered in both subgroups. The evidence that subjects homozygous for Gln27 in the ADRB2 gene show a significant reduction of HDL-CHO levels, as well as the increased TG levels in subjects homozygous for Glu27 after propranolol administration, suggest that the Gln27Glu polymorphism represents a risk factor for dyslipidemia induced by propranolol. These results may contribute to a better understanding of the mechanisms underlying dyslipidemia induced by ADRB2 antagonists.

Gas Chromatographic-Mass Spectrometric Differentiation of Atenolol, Metoprolol, Propranolol, and an Interfering Metabolite Product of Metoprolol

Over a 10-year period, 1993-2002, Federal Aviation Administration identified 50 pilot fatalities involving atenolol, metoprolol, and propranolol, which is consistent with the fact that these drugs have been in the lists of the top 200 drugs prescribed in the U.S. In a few of the 50 pilot fatality cases, initial analysis suggested the presence of atenolol and metoprolol. However, there was no medical history with these cases supporting the use of both drugs. Therefore, atenolol, metoprolol, and/or propranolol, with their possible metabolite(s), were re-extracted from the selected case specimens, derivatized with pentafluoropropionic anhydride (PFPA), and analyzed by gas chromatography-mass spectrometry (GC-MS). The MS spectra of these three antihypertensives and a metoprolol metabolite are nearly identical. All of the PFPA derivatives had baseline GC separation, with the exception of a metoprolol metabolite product, which co-eluted with atenolol. There were four primary mass fragments (m/z 408, 366, 202, and 176) found with all of the PFPA-beta-blockers and with the interfering metabolite product. However, atenolol has three unique fragments (m/z 244, 172, and 132), metoprolol has two unique fragments (m/z 559 and 107), propranolol has four unique fragments (m/z 551, 183, 144, and 127), and the metoprolol metabolite product has two unique fragments (m/z 557 and 149). These distinctive fragments were further validated by using a computer program that predicts logical mass fragments and performing GC-MS of deuterated PFPA-atenolol and PFPA-propranolol and of the PFPA-alpha-hydroxy metabolite of metoprolol. By using the unique mass fragments, none of the pilot fatality cases were found to contain more than one beta-blocker. Therefore, these mass ions can be used for differentiating and simultaneously analyzing these structurally similar beta-blockers in biological samples.

Development and application of a new on-line SPE system combined with LC–MS/MS detection for high throughput direct analysis of pharmaceutical compounds in plasma

A technique using a fully automated on-line solid phase extraction (SPE) system (Symbiosis, Spark Holland) combined with liquid chromatography (LC)-mass spectrometry (MS/MS) has been investigated for fast bioanalytical method development, method validation and sample analysis using both conventional C18 and monolithic columns. Online SPE LC-MS/MS methods were developed in the automated mode for the quantification of model compounds (propranolol and diclofenac) directly in rat plasma. Accuracy and precision using online SPE LC-MS/MS with conventional C18 and monolithic columns were in the range of 88-111% and 0.5-14%, respectively. Total analysis cycle time of 4 min per sample was demonstrated using the C18 column. Monolithic column allowed for 2 min total cycle time without compromising the quality and validation criteria of the method. Direct plasma sample injection without on-line SPE resulted in poor accuracy and precision in the range of 41-108% and 3-81%. Furthermore, the increase in back pressure resulted in column damage after the injection of only 60 samples.

Increase of the LC-MS/MS sensitivity and detection limits using on-line sample preparation with large volume plasma injection

Large volume injection (LVI) has systematically been studied to improve LC-MS/MS sensitivity (signal-to-noise ratio, or S/N) and detection limits. The method of LVI was combined with on-line solid phase extraction (on-line SPE) and LC-MS/MS detection for analysis of compounds directly in plasma. It was demonstrated that LVI of plasma with on-line SPE-LC-MS/MS allows for improvement of sensitivity and detection limits without compromising chromatographic peak shape and resolution and inducing significant matrix and signal suppression effects. Furthermore, sensitivity and detection limits improve linearly with the injection volume up to 100 microL. Quantification of the model compounds in plasma demonstrated comparable calibration curve statistics, precision and accuracy for 5, 50 and 100 microL plasma injections.

Cardiopulmonary bypass alters the pharmacokinetics of propranolol in patients undergoing cardiac surgery

The pharmacokinetics of propranolol may be altered by hypothermic cardiopulmonary bypass (CPB), resulting in unpredictable postoperative hemodynamic responses to usual doses. The objective of the present study was to investigate the pharmacokinetics of propranolol in patients undergoing coronary artery bypass grafting (CABG) by CPB under moderate hypothermia. We evaluated 11 patients, 4 women and 7 men (mean age 57 +/- 8 years, mean weight 75.4 +/- 11.9 kg and mean body surface area 1.83 +/- 0.19 m(2)), receiving propranolol before surgery (80-240 mg a day) and postoperatively (10 mg a day). Plasma propranolol levels were measured before and after CPB by high-performance liquid chromatography. Pharmacokinetic Solutions 2.0 software was used to estimate the pharmacokinetic parameters after administration of the drug pre- and postoperatively. There was an increase of biological half-life from 4.5 (95% CI = 3.9-6.9) to 10.6 h (95% CI = 8.2-14.7; P < 0.01) and an increase in volume of distribution from 4.9 (95% CI = 3.2-14.3) to 8.3 l/kg (95% CI = 6.5-32.1; P < 0.05), while total clearance remained unchanged 9.2 (95% CI = 7.7-24.6) vs 10.7 ml min(-1) kg(-1) (95% CI = 7.7-26.6; NS) after surgery. In conclusion, increases in drug distribution could be explained in part by hemodilution during CPB. On the other hand, the increase of biological half-life can be attributed to changes in hepatic metabolism induced by CPB under moderate hypothermia. These alterations in the pharmacokinetics of propranolol after CABG with hypothermic CPB might induce a greater myocardial depression in response to propranolol than would be expected with an equivalent dose during the postoperative period.

QT PRODACT: Usability of Miniature Pigs in Safety Pharmacology Studies: Assessment for Drug-Induced QT Interval Prolongation

To investigate whether miniature pigs are useful for evaluating the potential of drugs for drug-induced prolongation of the QT interval, we performed an in vivo QT assay using conscious and unrestricted miniature pigs. Compared with the vehicle average baseline values, haloperidol at 3 and 10 mg/kg, p.o. prolonged the QTcF interval (Fridericia's formula) by 8%-16%. The plasma concentration of haloperidol at which QT interval was prolonged (Cmax=42.9 ng/mL) was almost equal to that in humans. dl-Propranolol at 3, 10, and 30 mg/kg, p.o. caused no alterations in QT interval. dl-Propranolol at 3, 10, and 30 mg/kg, at which plasma concentrations were lower than in humans treated with dl-propranolol at the therapeutic dose level, shortened QTcF interval by 7%-12%. dl-Sotalol at 10 mg/kg, p.o. prolonged QTcF interval by 7%. From the above results, we considered that the miniature pig can be used for prediction of drug-induced prolongation of QT interval in humans, and thus, it is one of the useful animal species for assessing electrocardiograms in safety pharmacology studies.

Once-daily propranolol extended-release tablet dosage form: formulation design and in vitro/in vivo investigation

The purpose of this study was to develop and optimize the propranolol once-daily extended release formulations containing HPMC, Microcrystalline cellulose (MCC) and lactose. In vitro studies, the response surface methodology and multiple response optimization utilizing the polynomial equation were used to search for the optimal formulation with specific release rate at different time intervals. The constrained mixture experimental design was used to prepare systematic model formulations, which were composed of three formulation variables: the content of HPMC (X(1)) MCC (X(2)) and lactose (X(3)). The drug release percent at 1.5, 4, 8, 14 and 24 h were the target responses and were restricted to 15-30, 35-55, 55-75, 75-90 and 90-110%, respectively. The results showed that the optimized formulation provided a dissolution pattern equivalent to the predicted curve, which indicated that the optimal formulation could be obtained using response surface methodology. The mechanism of drug release from HMPC matrix tablets followed non-Fickian diffusion. In the vivo study, the MRT was prolonged for matrix tablets when compared with commercial immediate release tablets. Furthermore, a linear relationship between in vitro dissolution and in vivo absorption was observed in the beagle dogs.

Comparison of extraction of a β-blocker from plasma onto a molecularly imprinted polymer with liquid–liquid extraction and solid phase extraction methods

An optimised solid phase extraction (SPE) method developed for the extraction of a structural analogue of the beta-blocking drug propranolol from plasma utilising a molecularly imprinted polymer (MIP) has been compared with methods based on conventional liquid-liquid extraction (LLE), and SPE using C18-bonded and immobilised phenyl boronic acid (PBA). All four methods could be used for the extraction of the analyte with acceptable accuracy and precision. The MIP-based method, unlike the other methods required a protein precipitation step prior to extraction to eliminate the effects of co-extracted protein. The best performance was seen with the LLE method followed by SPE on the C18 phase. The MIP-based method represented no advantage over the comparator methods for this analyte. Indeed the performance of the MIP-based method was marginally worse as leaching of low level template impurities prevented detection of the target analyte at low concentrations (5 ngmL(-1)). This relatively poorer performance was evident as worse accuracy at low concentrations with a consequent higher limit of quantification than the conventional methods.

The Effect of Food on the Relative Bioavailability of Rapidly Dissolving Immediate-Release Solid Oral Products Containing Highly Soluble Drugs

The purpose of this study is to test the hypothesis that rapidly dissolving immediate-release (IR) solid oral products containing a highly soluble and highly permeable drug [biopharmaceutical classification system (BCS) class I] are bioequivalent under fed conditions. Metoprolol and propranolol (BCS class I) as well as hydrochlorothiazide (BCS class III) were selected as model drugs. The relative bioavailability of two FDA approved (Orange Book AB rating) solid oral dosage forms of metoprolol and propranolol/hydrochlorothiazide (combination tablets) was evaluated in human volunteers under fed conditions using a two-way crossover design. Equal numbers of male and female volunteers were recruited, and racial and/or ethnic minorities were not excluded. The plasma concentrations of metoprolol, propranolol, and hydrochlorothiazide were determined using validated high-performance liquid chromatography (HPLC) methods. Eighteen subjects completed the metoprolol study while 17 subjects completed the propranolol/hydrochlorothiazide combination tablet study. In the metoprolol study, the 90% confidence intervals of Cmax and AUC(inf) were 98-118% and 92-115%, respectively. For propranolol, the 90% confidence intervals of Cmax and AUC(inf) were 91-121% and 89-117%, and for hydrochlorothiazide, the 90% confidence intervals for Cmax and AUC(inf) were 96-107% and 97-106%, respectively. These study results appear to support the hypothesis that rapidly dissolving IR solid oral products containing a BCS class I drug are likely to be bioequivalent under fed conditions. In addition, BCS class III drugs may have the potential to be bioequivalent under fed conditions.

Evaluating Barriers to Bioavailability in Vivo: Validation of a Technique for Separately Assessing Gastrointestinal Absorption and Hepatic Extraction

PURPOSE

The purpose of this study was to develop and validate a method for separately evaluating the roles of gastrointestinal absorption and hepatic extraction as barriers to oral bioavailability (BA). The method was validated using five reference compounds known to have different absorption and hepatic extraction properties. Dose-dependence was also investigated for one reference compound.

METHODS

Five reference compounds, amoxicillin, antipyrine, atenolol, propranolol, and testosterone, were administered as a cassette intravenouly (IV), via the hepatoportal vein (IPV), intraduodenally (ID), and intracolonically (IC) to male Sprague-Dawley rats. Blood samples were taken at nine time points, and the compounds were extracted from plasma using solid phase extraction. Plasma concentrations of each compound were determined using Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS). Pharmacokinetic parameters including bioavailability were calculated for each compound for each route of administration.

RESULTS

Testosterone BA was less than 10% by ID, IC, and IPV routes, due to high hepatic extraction, consistent with its high systemic clearance (63 ml x min(-1) x kg(-1)) and short terminal plasma half-life (23 min). The IPV BA of amoxicillin was 95%+/-6% indicating the absence of hepatic extraction in the rat, but with an ID BA of approximately 39% suggesting incomplete GI absorption to be the main barrier to bioavailability. Absorption was poor from the colon, demonstrating site-dependence consistent with literature reports of site-dependent absorption. Low oral BA of propranolol was due in part to first-pass hepatic extraction (IPV BA of 36%). The IPV BA of propranolol was dose-dependent, most likely due to saturation of the P450 enzymes. Atenolol was incompletely bioavailable due to incomplete intestinal absorption, with no contribution of hepatic first-pass metabolism. Antipyrine was highly bioavailable by all routes.

CONCLUSIONS

This in vivo rat model is demonstrated to be useful for identifying and quantifying the causes of incomplete bioavailabilty. It separately evaluates intestinal absorption, hepatic extraction, and site-dependent absorption. Concentration-dependence of saturable processes can also be examined.

In vitro and in vivo evaluation of a matrix-in-cylinder system for sustained drug delivery

A matrix-in-cylinder system for sustained drug delivery, consisting of a hot-melt extruded ethylcellulose (EC) pipe surrounding a drug containing HPMC-Gelucire 44/14 core, was evaluated in vitro and in vivo. In an aqueous medium, the HPMC-Gelucire core forms a gel plug, which releases the drug-through the open ends of the EC pipe--by means of erosion. The influence of hydrodynamic and mechanical stress and the effect of different 'physiologically relevant' dissolution media on the in vitro drug release were investigated. From these in vitro dissolution tests, it was concluded that the EC pipe has a protective effect on the drug containing HPMC-Gelucire core. It largely protects the core against hydrodynamics and mechanical stress. Furthermore, drug release from the matrix-in-cylinder system was only slightly affected by the composition of the dissolution medium. A randomised crossover in vivo study in dogs revealed that the matrix-in-cylinder system containing propranolol hydrochloride has an ideal sustained release profile with constant plasma levels maintained over 24 h. Moreover, administration of the matrix-in-cylinder system resulted in a 4-fold increase in propranolol bioavailability when compared with a commercial sustained release formulation (Inderal).

A model to study intestinal and hepatic metabolism of propranolol in the dog

A model to investigate hepatic drug uptake and metabolism in the dog was developed for this study. Catheters were placed in the portal and hepatic veins during exploratory laparotomy to collect pre- and posthepatic blood samples at defined intervals. Drug concentrations in the portal vein were taken to reflect intestinal uptake and metabolism of an p.o. administered drug (propranolol), while differences in drug and metabolite concentrations between portal and hepatic veins reflected hepatic uptake and metabolism. A significant difference in propranolol concentration between hepatic and portal veins confirmed a high hepatic extraction of this therapeutic agent in the dog. This technically uncomplicated model may be used experimentally or clinically to determine hepatic function and metabolism of drugs that may be administered during anaesthesia and surgery.

[Effect of hyperlipidemia on pharmacodynamics of propranolol and atenolol]

The study was aimed to examine the effects of different presentations of hyperlipidemia on the pharmacodynamics of lipophilic propranolol and hydrophilic atenolol. Thirty subjects were divided into four study groups: the normolipemic subjects, patients with hypercholesterolemia, hypertriglyceridemia and patients with mixed form of hyperlipidemia. The drugs were administered orally at a single dose of 80 mg propranolol and 100 mg atenolol, using a cross-over study design. The plasma concentrations of propranolol and atenolol were determined using high-performance liquid chromatography (HPLC). Heart rate as well as systolic and diastolic blood pressure were evaluated in relation to the serum drug concentrations. In the light of the results obtained, the following conclusions were drawn: 1) hyperlipidemia affects pharmacodynamic properties of lipophilic propranolol and hydrophilic atenolol, 2) a modification of the drug dosage in hyperlipidemia is warranted.

Simultaneous high-performance liquid chromatographic assay of furosemide and propranolol HCL and its application in a pharmacokinetic study

A practical, sensitive, selective and efficient reversed-phase high-performance liquid chromatographic (HPLC) method is reported for the determination of two commonly used antihypertensive drugs, furosemide and propranolol hydrochloride. The drugs were eluted through a Nucleosil C(18) column with a mobile phase composed of 0.02 M potassium dihydrogen phosphate and acetonitrile (80:20, v/v) adjusted to pH 4.5 and the effluent from the column was monitored at 235 nm. The present method enabled simple and isocratic HPLC with UV detection of these drugs in raw materials and in pharmaceutical formulations. These procedures were also applied for the assay of furosemide in rabbits' plasma, using propranolol hydrochloride as an internal standard. The linear concentration range of the assay was 0.1-200 and 5-200 microg ml(-1) for furosemide and propranolol hydrochloride, respectively. The inter and intra-day assay precision and accuracy showed reproducibility and good linearity (r(2)>0.99). The method retained its accuracy and precision when applying the standard addition technique. The results obtained by applying the proposed method was statistically analysed and compared with those obtained by the reported methods.

[Toxicologic analysis of some adrenergic-beta blockers in the diagnosis of intoxications]

The study aimed at finding effective techniques of qualitative and quantitative analysis of selected beta-adrenergic blockers, useful both for monitoring of therapy and for thanatological diagnosis of intoxications. The studies took advantage of gas chromatography (GLC) and high performance liquid chromatography (HPLC). For isolation of studied compounds from biological material, classical and solid phase extraction procedures (SPE) Extrelut-20 (Merck), Abselut Nexus (Varian), STRATA C--18 E (Phenomenex) were used. The program included the analysis of most frequently applied derivatives: Acebutolol, Atenolol, Bunitrolol, Bupranolol, Labetolol, Metipranolol, Metoprolol, Oxprenolol, Practolol, Propranolol.

Alcohol withdrawal changes cardiovascular responses to propranolol challenge

The cardiovascular effects and plasma concentrations of a single dose of propranolol (80 mg) were studied non-invasively in alcohol-dependent subjects during alcohol withdrawal (AW) on day 1 and after resolution of withdrawal symptoms on day 10. At the onset of AW, propranolol caused a bradycardic effect which was significantly weakened on day 10. This might result from an increased bioavailability of propranolol on day 1 and from marked sympathetic activity. Propranolol also produced a negative inotropic effect, relatively weaker on day 1 than on day 10, being associated with increased beta-receptor sensitivity towards the final phase of AW. These results suggest that peripheral and central beta-adrenergic systems modulate the cardiovascular system in AW.

Short-term selection for the interaction between S-propranolol and ethanol in mice

BACKGROUND

We have previously demonstrated that there is an interaction between S-propranolol, a beta-adrenergic blocking agent, and ethanol on the hypnotic sensitivity of inbred short- and long-sleep mice (ISS and ILS). We found that the interaction was due to an additive hypothermic effect of ethanol and S-propranolol that markedly decreased the disappearance rate of ethanol. There was no discernible effect of S-propranolol on the hypnotic actions of ethanol as evidenced by the waking blood ethanol levels. Because ISS mice were more sensitive to this effect than were ILS mice, it seemed that there was a genetic effect to the response. Therefore, we carried out a short-term breeding project to determine whether the response could be selectively bred.

METHODS

We used the heterogeneous stock of mice from the Institute for Behavioral Genetics to carry out the selection study. The index for selection was the difference in sleep time between the same animal treated with propranolol and ethanol versus treatment with saline and ethanol at least 1 week apart.

RESULTS

In four generations, we were able to achieve separation between mice with a large difference in sleep time (high line) from those with a smaller difference in sleep (low line) time. There was no difference between the average blood ethanol at awakening in the high line versus the low line. The effect was not due to a difference in rate of propranolol metabolism between the two lines. Sleep time with ethanol alone was not different between the high and low lines.

CONCLUSIONS

The magnitude of the interaction between ethanol and S-propranolol is controlled by alleles with polymorphisms present in the HS stock of mice. The response is most likely due to a difference in the mechanisms of thermogenesis controlled by the beta-adrenergic receptors in muscle and fat. Because there were no sleep time differences between the high and low lines given ethanol alone, central nervous system sensitivity to ethanol is not a correlated response to the selection.

Interaction between S-propranolol and ethanol in mice selectively bred for ethanol sensitivity: the inbred short- and long-sleep mice

BACKGROUND

We have studied the effect of a beta-adrenergic blocking agent, S-propranolol, on the response of mice to anesthetic doses of ethanol. We used the selectively bred short and long sleep (ISS and ILS) mice. These mice were selected for their differential sensitivity to anesthetic doses of ethanol and then inbred. The study was prompted by the finding that the effect of ethanol on the firing rate of cerebellar Purkinje cells is modulated by beta-adrenergic input. In addition, this firing rate depression by ethanol is highly correlated with the anesthetic potency of ethanol. We were attempting to find a behavioral correlate of this effect of beta-adrenergic agents in the ISS and ILS mice.

METHODS

We studied the effect of S-propranolol plus ethanol on the sleep time and blood ethanol at awakening in the inbred ILS and ISS mice. We administered anesthetic doses of ethanol with and without S-propranolol. We conducted studies of the rate of disappearance of ethanol in the presence of S-propranolol and carried out sleep time and metabolic studies with mice in an incubator held at 32 to 33 degrees C.

RESULTS

We found that S-propranolol caused a prolonged anesthetic time brought about by ethanol but only in ISS mice. There was no significant difference in the blood ethanol levels at awakening with or without S-propranolol, indicating that S-propranolol had no effect on the brain sensitivity. Subsequently, we showed that this was due to a profound hypothermia caused by a combination of S-propranolol and ethanol. This was greater in the ISS mice because a larger dose of ethanol was required for the anesthetic effect of ethanol. The effect on ethanol disappearance rate, temperature drop, and anesthesia time all were largely reversed by placing the animals in an incubator at 32 to 33 degrees C.

CONCLUSIONS

Profound hypothermia lowers the ethanol disappearance rate when both S-propranolol and ethanol are given. The effect of S-propranolol is likely due to the blockade of beta-adrenergic receptors that prevents thermogenic responses to the hypothermia brought about by ethanol. The results indicated that there might be a genetic effect controlling the hypothermic response to the combination of S-propranolol and ethanol. Further experiments to investigate this are reported in a subsequent article. We could find no evidence of a central nervous system effect of S-propranolol on the hypnotic actions of ethanol in these strains of mice.

Comparative pharmacokinetics and pharmacodynamics of propranolol and atenolol in normolipaemic and hyperlipidaemic obese subjects

The lipophilic beta-adrenoreceptor antagonist propranolol and hydrophilic atenolol have been studied to define their pharmacokinetic and pharmacodynamic characteristics in obese patients. A total of 43 subjects were allocated into three study groups: (1) healthy, lean, normolipaemic volunteers, (2) obese normolipaemic subjects, and (3) obese patients with lipid disorders. A crossover method with an interval of 2 weeks was applied for oral 80 mg propranolol and oral 100 mg atenolol administration. Heart rate as well as systolic and diastolic blood pressure were recorded during 24 h. At each time-point of measurement blood serum concentration of propranolol and atenolol were evaluated. Pharmacokinetic parameters of the drugs were calculated using a one-compartment open model for extravascular administration. There were no statistically significant differences in blood serum concentrations of propranolol between the studied groups. The concentrations of atenolol were significantly lower in both normolipaemic and hyperlipidaemic obese subjects. A trend towards increase in Vd/F and Cl/F of propranolol in obese patients with hyperlipidaemia were noted. In the case of water-soluble atenolol, the AUC, C(max), Cl/(F x BW) were significantly lower in obese hyperlipidaemic and normolipaemic patients in comparison with lean subjects. The pharmacodynamic effects of propranolol and atenolol in obese and lean subjects were of similar magnitude. The observed differences between obese and non-obese persons were clinically not relevant.

Comparative in vivo evaluation of propranolol hydrochloride after oral and transdermal administration in rabbits

The purpose of this study was the in vivo evaluation of orally and transdermally administered propranolol hydrochloride in rabbits. Transdermal patches of propranolol hydrochloride (PPN) were formulated employing ethyl cellulose and polyvinylpyrrolidone as film formers. The pharmacodynamic (PD) and pharmacokinetic (PK) performance of PPN following transdermal administration was compared with that of oral administration. This study was carried out in a randomized cross-over design in male New Zealand albino rabbits. The PK parameters such as maximum plasma concentration (C(max)), time for peak plasma concentration (t(max)), mean residence time (MRT) and area under the curve (AUC(0-alpha)) were significantly (P<0.01) different following transdermal administration compared to oral administration. The terminal elimination half-life (t(1/2)) of transdermally delivered PPN was found to be similar to that following oral administration. In contrast to oral delivery, a sustained therapeutic activity was observed over a period of 24 h after transdermal administration compared to oral administration. The relative bioavailability of PPN was increased about fivefold to sixfold after transdermal administration as compared to oral delivery. This may be due to the avoidance of first pass effect of PPN. The sustained therapeutic activity was due to the controlled release of drug into systemic circulation following transdermal administration.

Automated online dual-column extraction coupled with teicoplanin stationary phase for simultaneous determination of (R)- and (S)-propranolol in rat plasma using liquid chromatography-tandem mass spectrometry

An automated online sample extraction method for rat plasma was developed and validated for the quantification of (R)- and (S)-propranolol following the intravenous administration of either the racemate or the individual enantiomers at 5 mg/kg. A dual-column extraction system coupled to a chiral stationary phase (CSP) was used in conjunction with liquid chromatography-tandem mass spectrometry. In this method, two Oasis HLB extraction columns (50x1.0 mm) in parallel were used for online plasma sample purification and teicoplanin CSP (Chirobiotic T) was used for the enantiomeric separation. This method allowed the use of one of the extraction columns for purification while the other was being equilibrated. Hence, the time required for re-conditioning the extraction columns did not contribute to the total analysis time per sample, which resulted in a relatively shorter run time and higher throughput. The lower limit of detection was 0.5 ng/ml and the lower limit of quantification was 2 ng/ml for each enantiomer using 25 microl of rat plasma. The method was validated with a linear calibration curve between 2 and 2000 ng/ml for (R)- and (S)-propranolol, respectively. The intra- and inter-day precision (C.V.) was no more than 7.6% and the accuracy of the assay was between 92 and 103%. The teicoplanin CSP proved to be rugged with excellent reproducibility of chromatographic parameters.

Pharmacokinetics of propranolol after single and multiple dosing with sustained release propranolol or propranolol CR (innopran XL) , a new chronotherapeutic formulation

Blood pressure rises rapidly upon waking and may be responsible, in part, for the increased incidence of myocardial infarction and stroke during the morning hours. Current formulations and dosing of antihypertensive drugs do not provide maximum coverage during this vulnerable period. This study was performed to demonstrate that propranolol CR (Innopran XL), a novel chronotherapeutic formulation of propranolol designed for nighttime dosing, has appropriate pharmacokinetics to provide maximum cardioprotective effect in the morning. Pharmacokinetics of propranolol CR and sustained-release propranolol after single and multiple doses were determined in normal male volunteers in this open-label, 2-period crossover study. The drugs were dosed in the evening and serial blood samples were taken for determination of propranolol concentration the next 24 to 72 hours. After a single 160-mg dose of propranolol CR administered at 10 pm, absorption was delayed by about 4 hours, after which plasma concentration rose steadily, reaching a peak at about 10:00 am. In contrast, after dosing with sustained release propranolol, plasma levels of propranolol began to rise almost immediately, reaching a plateau between 4:00 am and 10:00 am. During multiple dosing, steady-state trough plasma concentrations were achieved after 2 days with either drug. After the final dose, the plasma profiles of both drugs were similar to those observed in the single-dose study. Bioavailability was similar for both formulations of propranolol. Propranolol CR exhibited appropriate pharmacokinetics for a chronotherapeutic approach to the treatment of hypertension.

The increased intestinal absorption rate is responsible for the reduced hepatic first-pass extraction of propranolol in rats with cisplatin-induced renal dysfunction

The mechanisms responsible for the increased bioavailability of propranolol in renal dysfunction were investigated in rats. Experimental acute renal failure (ARF) was induced by intraperitoneal injection of cisplatin (5 mg kg(-1)). ARF induced a significant increase in blood propranolol concentration after intra-intestinal administration. The extent of bioavailability (F) of propranolol at an intestinal dose of 15 mg kg(-1) was 16.4% and 26.9% in control and ARF rats, respectively, and the F value at a 37.5 mg kg(-1) dose was 54.7% and 81.4% in control and ARF rats, respectively. In contrast, the blood propranolol concentration following intraportal infusion was not increased significantly in ARF rats. The hepatic first-pass extraction (E(h)) was dose-dependent and saturable: E(h) of propranolol in control rats was 58.0% and 18.3% at 8 and 20 mg kg(-1), respectively, and E(h) in ARF rats was 50.8% and 19.9% at 8 and 20 mg kg(-1), respectively. The initial absorption rate of propranolol from the intestine in ARF rats was significantly greater compared with control rats. These results indicated that the increased bioavailability of propranolol in rats with cisplatin-induced renal dysfunction was mainly a result of the increased absorption rate in the intestine followed by the partial saturation of hepatic first-pass metabolism.

Comparative pharmacokinetics of propranolol and atenolol in primary hyperlipidemia

The study was aimed to examine the effects of different types of hyperlipidemia on the pharmacokinetics of lipophilic propranolol and hydrophilic atenolol. Thirty subjects were divided into four study groups: normolipemics, hypercholesterolemics, hypertriglyceridemics, and patients with mixed form of hyperlipidemia. The drugs were administered orally at a single dose of 80 mg for propranolol and 100 mg for atenolol, using a cross-over study design. Pharmacokinetic parameters of the drugs were calculated using a noncompartmental open model. The results of the present study demonstrated a possible influence of dyslipidemia on pharmacokinetics of both the lipophilic and hydrophilic drugs. As for the lipophilic drug propranolol, a significant decrease in elimination rate constant was found (from 0.24 +/- 0.08 h(-1) to 0.16 +/- 0.04 h(-1), p < 0.03) in comparison to normolipemic subjects. In the case of the hydrophilic atenolol, the most marked alterations were also seen in subjects with mixed form of hyperlipidemia, especially significantly lower values of area under the concentration-time curve (8950.8 +/- 2060.5 ng/ml x h and 6715.4 +/- 1813.8 ng/ml x h, p < 0.05) as well as higher elimination rate constant (0.08 +/- 0.03 h(-1) and 0.13 +/- 0.05 h(-1), p < 0.05) in comparison with the controls, respectively. Total body clearance per kg of body weight of propranolol as well as atenolol was not influenced by dyslipidemias. The results of the study indicate that lipid metabolism disturbances might to some extent influence the pharmacokinetics of propranolol and atenolol, with the most significant alterations seen in the patients with mixed form of hyperlipidemia.