[A new cause of resistant arterial hypertension: coprescription with anticonvulsant treatments]

This article provides two case reports about pharmacokinetic interactions with hypertensive drug therapy and anticonvulsive treatment. First, a 49-year-old patient presenting severe hypertension had a non-traumatic cerebral hemorrhage with convulsions. Extensive etiologic investigations did not find any cause of secondary hypertension. Under an association of four antihypertensive drugs regimen, associated with carbamazepine blood pressure was not controlled. Finally, blood pressure was well controlled after replacement of carbamazepine with vigabatrin. The second case reports a 64-year-old treatment-resistant essential hypertensive patient, carbamazepine was associated with antihypertensive treatment because of aggressivity attributed to Alzheimer's disease. After withdrawal of carbamazepine treatment, blood pressure reached normal values with the same antihypertensive regimen. Those case reports suggest drug-drug interactions between antihypertensive and anticonvulsive drug therapies. Following explanation can be hypothesis: several antihypertensive drugs are liver-metabolised by microsomal cytochrome P450 3A4 isoform that could explain a significantly decreased half-life in association with enzymatic inducers, such as rifampicine or antiepileptic drugs (phenobarbital, phenytoin or carbamazepine).

CONCLUSION

When blood pressure is not controlled without cause of secondary hypertension, physicians must be careful with drug-drug interactions.

Evaluation of the effect of polyethylene glycol 400 on the nasal absorption of nicardipine and verapamil in the rat

This study has investigated the effect of polyethylene glycol (PEG) 400 on the intranasal absorption and ensuing pharmacokinetics of the calcium entry blockers nicardipine and verapamil in a rat model. To solutions of nicardipine in acetate buffer pH 5.0 and of verapamil in distilled water, PEG 400 was added in concentrations of 0-5%. The nasal bioavailability of nicardipine from plain buffered solution was 44%, and increased steadily to 56-79% in direct proportion to the amount of PEG 400 added. Verapamil, on the other hand, exhibited an intranasal bioavailability of 52% in the absence of PEG 400, and between 61-68% in the presence of increasing concentrations of PEG 400. None of the formulations tested was found to cause adverse effects on the morphology and integrity of the nasal mucosa.

Formulation of controlled release microspheres containing nicardipine: the role of pharmacokinetic modeling and computer simulation

Nicardipine is an antihypertensive drug of the dihydropyridine series. It has high solubility in an acidic and low solubility in an alkaline medium. It is rapidly absorbed, extensively presystemically metabolized and excreted in the urine and faeces, mainly as inactive metabolites. Since the duration of its action can be extended by prolonging the absorption interval, the design of controlled release formulation is reasonable. The aim of the present study was to prepare microspheres which would release nicardipine at a decreased rate in gastric and increased rate in intestinal juice during a 12 h interval. Pharmacokinetic modeling based on compartment analysis and supported by analog computer and digital simulation technique showed that the target steady state peak plasma concentrations of 32 microg/l and trough plasma concentration of 7 microg/l would be maintained if nicardipine were incorporated in a formulation releasing the drug as follows: 25% after 1 h, 40% after 2 h, 65% after 4 h, 80% after 6 h, 90% after 8 h and 100% by 12 h. Microspheres have been prepared from hydroxypropylmethylcellulose phthalate polymer using the solvent evaporation method. Drug content, scanning electron micrographs, particle size distribution and dissolution profile were determined. In vitro nicardipine release was described by a biphasic square root of time kinetics and was in accordance with the above values relating to the dissolution. Furthermore, a composed first-pass pharmacokinetic model with derived release function as an input was developed to predict nicardipine plasma concentrations after single- and 12 h multiple-dosage-regimen scheme administration of controlled release microspheres.

A high-performance liquid chromatographic method for the determination of nicardipine in plasma and its application to pharmacokinetics in humans

A simple and sensitive reversed-phase liquid chromatographic method has been developed and validated for the analysis of nicardipine in human plasma and the study of the pharmacokinetics of the drug in human body. Nicardipine and nimodipine (internal standard) in plasma were extracted with hexane-butanol (12:1, v/v) after addition of borate buffer (0.5 mol/mL, pH = 9.0), and then measured by HPLC using a Hypersil C18 column as stationary phase and acetonitrile--KH2PO4 buffer (0.015 M, pH = 5.5)--triethylamine as mobile phase. Nicardipine was quantified by ultraviolet absorbance at 236 nm. The method proved to be linear in the clinical range of 5-200 ng/mL with a regression coefficient of 0.9998. The lower limit of detection of nicardipine in plasma was 2.5 ng/mL. Intra- and inter-day coefficients of variation of assay for nicardipine in plasma were 3.5-5.4% (n = 7) and 5.2-6.4% (n = 5), respectively. The recovery of nicardipine was 92.8-100.8% for plasma. The method has been used to determine nicardipine in plasma samples from 10 volunteers and provided data on the pharmacokinetics of the drug. The results inferred that nicardipine is absorbed rapidly and has a relatively short half-life in healthy individuals. The data obtained was fitted with a 3P87 program to study the pharmacokinetics. The results showed that the disposition of nicardipine was conformed to a two-compartment open model with Tmax = 1.6 +/- 0.3 h, Cmax = 109.8 +/- 38.7 ng/mL, T1/2 = 5.35 +/- 2.28 h and AUC0-->infinity = 322.1 +/- 69.6 ng/h/mI.

Rational use of calcium-channel antagonists in Raynaud's phenomenon

Raynaud's phenomenon (RP) is a peripheral circulatory disorder characterized by sudden episodes of digital artery spasm, often precipitated by cold temperature or emotional stress. Although the cause of RP is not fully known, it appears to involve inappropriate adrenergic response to cold stimuli. Treatment of RP is conservative in most patients, but in patients with severe disease includes the use of agents that promote digital vasodilation. The calcium-channel antagonists, particularly the dihydropyridine derivative nifedipine, are the most thoroughly studied drug class for the treatment of RP. Approximately two thirds of patients respond favorably, with significant reductions in the frequency and severity of vasospastic attacks. Nifedipine use is often limited by the appearance of adverse vasodilatory effects such as headache or peripheral edema. The newer second-generation dihydropyridines such as amlodipine, isradipine, nicardipine, and felodipine also appear to be effective in patients with RP and may be associated with fewer adverse effects.

Extraction and quantification of nicardipine in human plasma

A novel simple method of extraction, separation, identification and quantification of nicardipine in human plasma samples was completely studied. The human plasma samples were initially purified by solid-phase extraction (SPE) using a C18 cartridge. The extracted samples were separated and nicardipine present in the samples was quantified by high-performance liquid chromatography (HPLC) on a reversed-phase C18 column employing a mobile phase consisting of 60% (v/v) acetonitrile in 0.02 M NaH2PO4 with pH of 6.3 and a variable wavelength UV detector set at 254 nm. The recovery of nicardipine from plasma samples using selective SPE was 91+/-6.0% and had less interfering compounds in the HPLC analysis compared to the use of liquid-liquid (L/L) extraction. In the HPLC analysis, examining the effect of pH values of the mobile phase on the capacity factor (k') of nicardipine revealed a method for selecting a critical k' value of nicardipine to eliminate interfering peaks near the peak specific to the analyte. This method for quantification of nicardipine in human plasma samples was suitable for studying the pharmacokinetic profile of nicardipine administered as an intravenous bolus to cardiac surgical patients.

Possibility of partial absorption of nicardipine by routes other than the hepato-portal system after oral administration in rats

The systemic availability of nicardipine after different routes of administration has been examined in rats, with particular attention to differentiating oral absorption from intestinal and hepatic metabolism. The quantities of nicardipine and its metabolite were determined by capillary column gas chromatography. A linear relationship was shown between the hepatic first-pass effect and dose after hepato-portal administration of nicardipine; the hepatic first-pass effect was calculated to be approximately 80%. However, the availability after oral and rectal administration was found to be more than twice that observed after hepato-portal administration. Partial avoidance of the hepatic first-pass effect after oral and rectal administration are estimated to be 37.3% and 35.2%, respectively, assuming that all absorbed molecules pass through the liver. These findings suggest that the absorption of nicardipine after oral administration also occurs by routes other than the hepato-portal system.

Formulation and investigation of nicardipine HCl-alginate gel beads with factorial design-based studies

The release rate of nicardipine HCl from various alginate gel bead formulations was investigated. The formulations were prepared by utilizing 23 factorial design. The effect of drug:polymer weight ratio, CaCl2 and sodium-alginate concentration on the time for 50% of the drug to be released (t50%) and the drug entrapment efficiency were evaluated with analysis of variance. The mean particle size and the swelling ratio of the beads were determined. The in vitro release studies were carried out by flow-through cell apparatus in different media (pH 1.2, 2.5, 4.5, 7 and 7.5 buffer solutions). Drug:polymer weight ratio and the interaction of drug:polymer weight ratio and CaCl2 concentration had a significant effect on the drug entrapment efficiency. The release of nicardipine was extended with the alginate gel beads, which were prepared in a ratio of 1:1 (drug:polymer). The release of drug from alginate gel beads took place both by diffusion through the swollen matrix and relaxation of the polymer at pH 1.2-4.5. However, the release was due to the diffusion and erosion mechanism at pH 7-7.5.

Influence of swelling degree on release of nicardipine hydrochloride from acrylic microspheres prepared by solvent evaporation method

The purpose of this study was to prepare and evaluate an enteric coated dosage form of nicardipine hydrochloride (NCH)-loaded microspheres for delivery over a 12-hr period. Microspheres containing Eudragit RS and L with different ratios were prepared by solvent evaporation method and the effect of swelling on the release rate and characteristics was investigated. The change in the diameters of microspheres with time in simulated intestinal fluid (pH 7.5) at 37 degrees C has been studied. Drug release was determined using the flow-through cell method, and related to the degree of swelling (Q) of the microspheres. Q values in turn depended on the ratio of Eudragit RS-L used. Release of NCH from microspheres increased with Eudragit L amount, but no controlled-release pattern was observed. Q values > or = 18.88 caused a slow initial release followed by an accelerated release. Microspheres with an Eudragit RS-L ratio of 1:5.7, Q value of 38.71, and drug release rate of 0.155% min-1 exhibited a remarkable delayed time for erosion to begin (120 min). Thus, microspheres prepared from this formulation may provide an effective enteric dosage form, releasing NCH at a predetermined rate.

Interactions between nicardipine and enflurane, isoflurane, and sevoflurane

PURPOSE

During nicardipine induced hypotension, different inhalational anaesthetics may have different effects on haemodynamic variables, sympathetic function and drug metabolism. Therefore, the haemodynamic effects and pharmacokinetics of nicardipine were studied in the presence of the three inhalation anaesthetics enflurane, isoflurane and sevoflurane.

METHODS

Thirty patients scheduled for neurosurgery were randomly assigned to one of three anaesthetic techniques: enflurane, isoflurane or sevoflurane. Nicardipine (0.017 mg.kg-1) was administered during stable anaesthesia and the following measurements made for 30 min: blood pressure, heart rate, and plasma concentration of norepinephrine, epinephrine and nicardipine.

RESULTS

With sevoflurane, plasma concentrations of nicardipine, five minutes after administration, (39.8 +/- 3.5 ng.ml-1, mean +/- SEM) were higher (P < 0.05) than in the other two groups (28.3 +/- 2.9 ng.ml-1, 32.6 +/- 4.3 ng.ml-1, enflurane and isoflurane, respectively). With isoflurane, the approximated half-life of nicardipine (14 +/- 4 min) was shorter and clearance (2.1 +/- 0.3 l.min-1) more rapid. Peak heart rates were similar in all groups but elevated rates continued longer with isoflurane (> 30 min). Nicardipine-induced reduction in blood pressure was greater with sevoflurane but low pressures persisted for longer with isoflurane. Plasma catecholamine concentrations increased with isoflurane and enflurane, but not with sevoflurane: considerably higher epinephrine concentrations were seen with isoflurane.

CONCLUSION

This study showed that the action of nicardipine is modified by different inhalational anaesthetic agents. Nicardipine has a prolonged duration of action in the presence of isoflurane and produces greater initial hypotension with sevoflurane.

Enantioselective high-performance liquid chromatographic determination of nicardipine in human plasma

A sensitive method for the enantioselective high-performance liquid chromatography (HPLC) determination of nicardipine in human plasma is described. (+)-Nicardipine, (-)-nicardipine and (+)-barnidipine as an internal standard are detected by an ultraviolet detector at 254 nm. Racemic nicardipine in human plasma was extracted by a rapid and simple procedure based on C18 bonded-phase extraction. The extraction samples were purified and concentrated on a pre-column using a C1 stationary phase and the enantiomers of nicardipine are quantitatively separated by HPLC on a Sumichiral OA-4500 column, containing a chemically modified Pirkle-type stationary phase. Determination of (+)- and (-)-nicardipine was possible in a concentration range of 5-100 ng ml(-1) and the limit of detection in plasma was 2.5 ng ml(-1). The recoveries of (+)- and (-)-nicardipine added to plasma were 91.4-98.4% and 93.3-96.7%, respectively, with coefficients of variation of less than 9.0 and 9.4% respectively. The method was applied to low level monitoring of (+)- and (-)-nicardipine in plasma from healthy volunteers.

Pharmacokinetics of nicardipine enantiomers in healthy young volunteers

OBJECTIVES

The present study was conducted to compare pharmacokinetic behaviors of nicardipine enantiomers given in different doses with different formulations of racemic nicardipine in healthy volunteers.

METHODS

One or two 20-mg racemic nicardipine tablets, and a 40-mg sustained-release capsule of nicardipine were administered to eight healthy volunteers in a crossover fashion and pharmacokinetic parameters were evaluated. Enantiomer concentrations were determined by GC-MS combined with chiral stationary phase HPLC.

RESULTS AND CONCLUSIONS

Serum concentration of (+)-nicardipine was approximately 2-3 times higher than that of (-)-nicardipine in 20- and 40-mg doses of conventional formulations and a non-linear increase in bioavailability with dose was demonstrated. The value for AUC of (+)-nicardipine was approximately 2.3-2.8 times greater than that of the (-)-nicardipine (P < 0.05) when 20 and 40 mg racemic nicardipine were administered in a conventional preparation. Relative bioavailability of the sustained-release preparation vs the conventional preparation was 28% and 44% for (+)- and (-)-nicardipine, respectively, for the 40-mg dose.

Bioequivalence of two orally administered nicardipine products

The relative bioavailabilities of orally administered nicardipine (Zenith Laboratories) and nicardipine (Cardene Syntex Laboratories) were compared following a single 30 mg dose under fasted conditions using a two-way crossover study with 34 healthy adult male subjects. In a separate study the effect of food on the relative bioavailabilities of these products was assessed following an identical dose by comparing the Zenith product under fasted conditions, the Zenith product under fed conditions, and the Syntex product under fed conditions using a three-way crossover study with 17 healthy adult male subjects. In the fasted study, 90% confidence intervals surrounding ratios (Zenith/Syntex) of least-squares means derived from 1n-transformed data were 0.84-1.02 for AUCt, 0.85-1.04 for AUCinfinity, and 0.86-1.05 for Cmax, clearly demonstrating bioequivalence of the two products. In the food-effect study ratios of least-squares means (Zenith under fed conditions/Zenith under fasted conditions) were 0.62 for AUCt, 0.65 for AUCinfinity, and 0.40 for Cmax, with tmax delayed from 0.906 +/- 0.337 h (Zenith under fasted conditions) to 2.33 +/- 0.717 h (Zenith under fed conditions) and 2.84 +/- 0.834 h (Syntex under fed conditions). Findings indicate that the presence of food in the gastrointestinal tract reduces the bioavailability of orally administered nicardipine. However, ratios under fed conditions (Zenith/Syntex) were very close to unity for each metric, suggesting that the observed food effect is independent of the product formulation. Findings further suggested that food effects on conventional pharmacokinetic metrics might be attributed to alteration of extent, rather than rate, of gastrointestinal absorption. Finally, these results question the applicability of the peak plasma concentration (Cmax) as an index of absorption rate in nicardipine studies.

Modulation of the dissolution profiles from Geomatrix multi-layer matrix tablets containing drugs of different solubility

A new multi-layer tablet design has recently been proposed for constant drug release: Geomatrix Technology (Jago Pharma, Muttenz, Switzerland). It consists in the application of a drug-free barrier layer on one or both bases of an active core (hydrophilic matrix). The partial coating modulates the core hydration process and reduces the surface area available for drug release. The result is an extended release that draws close to a linear profile. The device was mainly intended for soluble drugs, while an excessive reduction of the release rate may be obtained with drugs of low solubility. In this study a new time-dependent polymeric barrier is proposed to control the release of sparingly soluble drugs. Two different barrier compositions (one swellable and one erodible) are applied on active cores containing drugs of different water solubility, Trapidil, Ketoprofen and Nicardipine hydrochlorides, and the drug dissolution patterns of the different multi-layer devices are compared. During dissolution, the swellable barrier swells and gels, but is not eroded, thus acting as a modulating membrane during the release process. The erodible barrier, instead, is progressively removed by the dissolution medium, exposing in time an increasing extent of the planar surface(s) of the core to interaction with the outer environment and to drug release. Both types of coatings are able to control drug release from the devices: the swellable barrier shows a stronger modulation efficiency and is more suitable to modify the delivery pattern of highly soluble drugs; the erodible barrier shows a time-dependent coating effect that provides better control of the dissolution profile of sparingly soluble drugs.

Intravenous nicardipine does not alter hepatic blood flow after orthotopic liver transplant

OBJECTIVE

To evaluate the effects of nicardipine on hepatic blood flow in patients with recent liver transplants. Secondly, to evaluate the liver extraction of nicardipine in order to determine the influence of liver transplantation on its disposition.

DESIGN

Prospective self-controlled clinical study.

SETTING

University hospital intensive care unit.

PATIENTS

Eight patients in the early postoperative period of orthotopic liver transplantation.

MEASUREMENTS AND RESULTS

Patients were given 5 mg of i.v. nicardipine. Systemic and splanchnic haemodynamic and metabolic parameters were measured before nicardipine administration (T0) and at 5 min (T1), 30 min (T2), and 120 min (T3) after administration. A catheter was inserted into a hepatic vein to determine the total hepatic blood flow (HBF) and the hepatic extraction coefficient of nicardipine. Nicardipine caused no significant changes in HBF, oxygen delivery, oxygen uptake, hepatic venous oxygen saturation, or the hepatic venous partial pressure of oxygen. Likewise, neither blood lactate concentrations nor arterial and hepatic venous lactate-pyruvate ratios were modified by nicardipine. The hepatic extraction coefficient of nicardipine was approximately 0.70 in the first 3 min after complete infusion, then decreased and remained stable at approximately 0.50, showing a non-linear first-pass metabolism pattern.

CONCLUSIONS

Nicardipine administration after liver transplantation appears to have no deleterious effects on HBF. Nicardipine can be classified as a drug of intermediate hepatic extraction coefficient, whose elimination partly depends on hepatic enzyme activity.

Comparison between a bid and a tid regimen: improved compliance with no improved antihypertensive effect. The EOL Research Group

OBJECTIVES

To compare compliance with an antihypertensive treatment administered either twice daily or three times daily. The two formulations of the antihypertensive treatment used (nicardipine) "regular tablets" (t.d.) and "slow release tablets" (b.d.) are bioequivalent at the daily dosage used in the study.

STUDY DESIGN

Open, controlled, parallel designed study with centralised, randomised allocation to the treatment groups: TID group: A nicardipine 20 mg tablet, three times daily for 3 months. BID group: A capsule of slow release (SR) nicardipine, 50 mg twice daily for 3 months.

PATIENTS

7274 hypertensive patients were investigated by 2.651 general practitioners. Compliance with the nicardipine was assessed by means of standardised interviews with the patients and by a questionnaire for the investigators.

RESULTS

Compliance was slightly higher in the BID than in the TID group; 71.2% and 24.5% of patients in the first group declared their compliance was 100% and 80% compared to 82.3% and 15% in the second group. A statistically significant relationship was shown between compliance with nicardipine and the decrease in blood pressure after three months of therapy. However, no significant difference was noticed between the two groups of patients in the absolute decrease in blood pressure after the treatment period: 25.7/14.7 mm Hg in the TID group compared with 25.9/15.0 mm Hg in the BID group.

CONCLUSIONS

A difference in compliance between the bioequivalent BID and TID formulations of the same active agent was shown in hypertensive patients. However, the difference was not large enough to lead to a difference either in the number of controlled patients or in the decrease in blood pressure. Reducing the number of daily doses does not automatically lead to greater efficacy of treatment.

Nicardipine and treatment of cerebrovascular diseases with particular reference to hypertension-related disorders

Nicardipine is a second generation dihydropyridine-type Ca2+ antagonist with high vascular selectivity and strong cerebral and coronary vasodilatory activity. The compound is used in the treatment of hypertension, primarily in the elderly. In this review the main evidence of the cerebrovascular activity of nicardipine in preclinical studies using in vitro and in vivo models is detailed. A particular physico-chemical property of nicardipine is the almost complete protonation in acid environment. This allows its accumulation in ischemic brain regions and makes it a candidate for the treatment of cerebrovascular disorders characterised by impaired brain perfusion. The main clinical data on the use of nicardipine in cerebral ischemia and related disorders, subarachnoid haemorrhage and stroke, are also reviewed. These studies included 5940 patients affected by chronic cerebrovascular insufficiency (cerebral ischemia, cerebral atherosclerosis mainly associated with hypertension, transient ischemic attacks, sequelae of cerebral infarction, thrombosis or embolia, hypertensive encephalopathy), 1540 patients affected by sequelae of subarachnoid haemorrhage and 206 patients affected by stroke. Both preclinical studies and clinical trials have shown that nicardipine is a safe Ca2+ antagonist with powerful cerebrovascular activity. This suggests its possible use in cerebrovascular disorders in which blockade of Ca2+ channels of the L-type and/or selective cerebral vasodilatation is desirable. Further studies are necessary to establish if modulation of neuronal Ca2+ channels of the L-type by nicardipine may have a neuroprotective effect independent by the cerebrovascular activity of the compound.

Antihypertensive effect of the novel water-soluble calcium antagonist (+/-)-3-(4-allyl-1-piperazinyl)-2,2-dimethylpropyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate dihydrochloride in rats

The antihypertensive effect of (+/-)-3-(4-allyl-1-piperazinyl)-2,2-dimethylpropyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate dihydrochloride (NKY-722, CAS 117241-46-0) was examined in conscious spontaneously hypertensive rats (SHR), normotensive Wistar rats (NWR) and anesthetized NWR, and its vasodilatory effect was investigated in the perfused NWR mesenteric vascular bed. NKY-722 and nicardipine administered intravenously (10-100 micrograms/kg) and orally (0.3-10 mg/kg) lowered blood pressure dose-dependently with an increase in heart rate in conscious SHR and NWR. The effects of NKY-722 were slower in onset and longer-lasting than those of nicardipine, and were more marked in SHR than in NWR. The effect of NKY-722 was roughly the same as that of nicardipine on intravenous administration. However, NKY-722 was 4-8 times more potent than nicardipine on oral administration. In anesthetized NWR, the hypotensive effects of NKY-722 administered via the femoral vein, portal vein and duodenum were examined in comparison with those of nicardipine. The findings suggest that NKY-722 is more efficiently absorbed from the gastro-intestinal tract and more resistant to the hepatic first pass effect than nicardipine. In the perfused NWR vascular bed, NKY-722 and nicardipine (0.01-1.0 microgram) attenuated the pressor response to KCl dose-dependently. The effect of NKY-722 was slower in onset and longer-lasting than that of nicardipine. In conclusion; NKY-722 has a potent, slow-onset and long-lasting antihypertensive activity, which is mainly attributed to its slow-onset and long-lasting vasodilatory action. NKY-722 is expected to be a useful antihypertensive drug.

Interactions between endothelin and the dihydropyridine-type calcium antagonist nicardipine in the human renal artery: a radioligand and autoradiographic study

The interactions between dihydropyridine Ca2+ channels and endothelin were analysed using combined radioligand binding and autoradiographic techniques. Endothelin is a potent constrictor peptide of arterial smooth muscle. Endothelin-induced vasoconstriction is attenuated by dihydropyridine-type Ca2+ antagonists such as nicardipine. However, the molecular mechanisms of this effect are not yet understood. Sections of the human renal artery bound [3H]-nicardipine in a manner consistent with the labelling of dihydropyridine-type Ca2+ channels. The highest density of [3H]-nicardipine binding sites occurred within the tunica media of the renal artery, probably over smooth muscle. A lower density of [3H]-nicardipine binding sites was noticeable in the tunica adventitia, whereas no specific binding occurred in the tunica intima. Endothelin-1, from a concentration of 1 pM l-1, reduced [3H]-nicardipine binding as a function of concentration. A 10 nM endothelin concentration reduced [3H]-nicardipine binding by about 85%. The isoform, endothelin-3, had little effect on [3H]-nicardipine binding. The above findings suggest the occurrence of an interaction, probably at the receptor level, between [3H]-nicardipine binding and endothelin-1. This interaction probably accounts for the attenuation of endothelin-1-elicited vasoconstriction induced by nicardipine.

Clinical pharmacology of nicardipine in liver transplant patients

Slow calcium channel antagonists are widely used among transplanted patients suffering from hypertension, although some of them tend to reduce hepatic blood flow. The aim of our study was to determine the pharmacological properties of nicardipine in transplanted patients with hypertension. Ten hours after liver transplantation, six patients (three men, three women) received 5 mg of intravenous nicardipine to prevent high blood pressure during intensive care. Prior to the administration and during the study (at the completion of the infusion, 3, 5, 10, 15, 20, 30, 45, and 60 min after infusion), the systemic and splanchnic parameters were measured (Swan Ganz catheter). Blood samples were drawn simultaneously from radial artery and free hepatic veins, in order to obtain the hepatic extraction of nicardipine. The hepatic extraction ratio was around 70% for the first 3 min, then decreased and remained stable thereafter, around 45%, showing a non linear first-pass metabolism pattern. Plasma hepatic clearance of nicardipine (699-850 ml/min) was close to total plasma clearance throughout the study (978 +/- 222 ml/min, from 71 to 87%) and half of the estimated hepatic plasma flow values at the same times (1467-1770 ml/min, from 44 to 51%). No statistically significant changes were observed in cardiac output and hepatic blood flow during the study, although there was a decrease in mean arterial blood pressure from 87 +/- 6 mmHg baseline level to 76 +/- 3 mmHg, 60 min after administration. Nicardipine chlorhydrate seems to be appropriate in post operative liver transplant patients when blood pressure must be decreased. Nicardipine safely lowers peripheral resistance, and does not induce changes in hepatic blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

A mathematical model for dynamics of cardiovascular drug action: application to intravenous dihydropyridines in healthy volunteers

A physiologically based mathematical model was built to describe the pharmacodynamic effects in response to the administration of intravenous (iv) dihydropyridine drugs in healthy volunteers. This model incorporates a limited number of hemodynamic variables, namely, mean arterial blood pressure (MAP), cardiac output (CO) or heart rate (HR), stroke volume (SV), and total peripheral resistance (TPR), into a closed-loop system supposed to represent essential features of the cardiovascular regulation. We also defined an additional auxiliary control variable (U) which is thought to represent primarily the role of the baroreceptor reflex. It was assumed that the variable U was related to MAP changes through both deviation- and rate-sensitive mechanisms. Other model parameters are the baseline levels for MAP, CO (or HR), and TPR, as well as time constants to account for further temporal aspects of the regulation. Finally, TPR was assumed to be linked to the plasma concentrations of dihydropyridine drugs via a conventional pharmacokinetic/pharmacodynamic (PK/PD) model, relying upon an effect compartment and a linear, hyperbolic, or sigmoidal relationship between the reduction in TPR and the drug concentrations at the effect site. The model characteristics were explored by studying the influence of various parameters, including baseline levels and deviation- and rate-sensitive control parameters, on the hemodynamic responses to a fictive constant rate i.v. infusion of a vasodilator drug. Attempts were also made to mimic literature data with nifedipine, following i.v. administration under both constant and exponentially decreasing infusion rates. The applicability of the model was demonstrated by fitting hemodynamic data following i.v. infusion of nicardipine to healthy volunteers, under experimental conditions similar to those described above for nifedipine. The effect model for the action of nicardipine on TPR, combined with the physiological model including a feedback control loop, allowed an adequate quantitative description of time profiles for both cardiac output and mean arterial pressure. The suggested model is a useful tool for integrated data analysis of hemodynamic responses to vasodilator drugs in healthy volunteers. Computer simulations suggest that a graded variation of a few model parameters--including baseline levels of TPR and MAP and the deviation-sensitive parameter of the arterial pressure control--would also be able to account for the pattern of hemodynamic response observed in hypertensive patients, which is qualitatively different to that seen in normotensive subjects. Extrapolation of drug response from the healthy volunteer to the hypertensive patient is allowed by our model. Its usefulness for an early evaluation of drug efficacy during drug development is under current investigation.

Sustained-release nicardipine in mild-to-moderate hypertension

STUDY OBJECTIVE

To evaluate the antihypertensive effects and tolerability of a sustained release preparation of nicardipine (NIC SR), a dihydropyridine calcium channel antagonist.

DESIGN AND INTERVENTIONS

After at least 1 week without receiving antihypertensive medications and 2 weeks of single-blind placebo treatment, the patients were randomized to receive in a double-blind fashion, either placebo or NIC SR 30, 45, or 60 mg twice daily at 12-h intervals for 12 weeks. Supine and standing blood pressure were measured in all patients and 24-h ambulatory blood pressure monitoring was performed in a subset of 75 patients at baseline during treatment with single-blind placebo and during the double-blind treatment period.

SETTING

Academic and private hypertension research clinics.

PATIENTS

Two hundred sixty-four patients with supine diastolic blood pressures of 95 to 114 mm Hg, ranging in age from 22 to 75 years and in weight from 50 to 137 kg, approximately evenly divided by gender; one third were black.

RESULTS

In comparison with placebo, all doses of NIC SR significantly reduced systolic and diastolic blood pressures, with a trend toward greater effects from 45 to 60 mg twice daily than with 30 mg twice daily. At all doses, reduction of blood pressure from baseline levels was fully apparent within the first 2 weeks of therapy and was maintained throughout the remaining 10 weeks of the trial. Ambulatory blood pressure monitoring demonstrated that the antihypertensive effect was maintained throughout the dosing interval. Adverse effects were primarily extensions of pharmacologic activity (eg, pedal edema, flushing). Six percent of the placebo group and 10 percent of the combined NIC SR groups experienced at least one adverse event that was judged to be probably related to therapy. Withdrawals due to unacceptably high blood pressure totaled 5 percent of the combined NIC SR groups and 25 percent of the placebo group.

CONCLUSIONS

Sustained-release nicardipine at a dose of 30 to 60 mg every 12 h provided effective and generally well-tolerated antihypertensive control throughout the day in most patients with mild-to-moderate essential hypertension.

Application of a system analysis approach to population pharmacokinetics and pharmacodynamics of nicardipine hydrochloride in healthy males

Nicardipine hydrochloride, a dihydropyridine calcium channel blocker, possesses antihypertensive and arterial vasodilator properties. A system analysis approach, which makes fewer structural assumptions than compartmental methods, is presented for determining the pharmacokinetics and pharmacodynamics of nicardipine hydrochloride in healthy males following a discontinuous infusion at four dose levels. The results indicate that the average total body clearance of nicardipine is 0.920 L/h/kg and the volume of distribution is 0.275 L/kg. Nicardipine hydrochloride has a mean residence time in the body of 1.27 h, of which 0.324 h were spent in the systemic circulation and the remainder in the periphery. The determined pharmacokinetic model was linked to a pharmacodynamic model that allowed the change in the mean arterial blood pressure and heart rate to be described and predicted. A population pharmacokinetic-pharmacodynamic model was derived and the predictive power of the proposed model was assessed with a cross-validation technique that employs a relative predictive quotient for comparing the predictions to the fitted model. The results indicate that the proposed model describes the pharmacodynamics of nicardipine in healthy males and has good predictive ability when tested with a cross-validation procedure.

Effect of receiver fluid pH on in vitro skin flux of weakly ionizable drugs

In in vitro skin permeation experiments, the pH of viable epidermis is readily conditioned by the receiver fluid. For weakly ionizable compounds, the flux determined experimentally thus depends on the receiver fluid pH. The purpose of the present work is to characterize this pH effect, since nonphysiological conditions have often been used in the receiver fluid to enhance the solubility of the subject compounds. A transport model was developed to analyze the above-mentioned pH effect of the receiver fluid on the steady state flux of weakly ionizable drugs. The results showed that the skin flux had a strong dependence on pH for those compounds with high intrinsic partition coefficients. Experimentally, this pH effect was observed with a model acid and a model base. The skin flux was found to have a profound dependence on the receiver fluid pH. This dependence also correlates with the octanol/water partition coefficient of the molecule. It was concluded that the use of a physiological receiver fluid would be crucial for a realistic estimation of transdermal potential. The results also suggested that, for weakly ionizable compounds with high partition coefficients, the viable epidermis could be a significant transport barrier for systemic absorption.

[Affinity of Z-105 to the 1,4-dihydropyridine type calcium channel and several other receptor bindings in the central nervous system]

The affinity of a 1,4-dihydropyridine (DHP) type calcium channel blocker, NZ-105 ((+/-)-2-[benzyl (phenyl) amino] ethyl 1,4-dihydro-2, 6-dimethyl-5- (5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinan- 2-yl)-4-(3-nitrophenyl)-3-pyridinecarboxylate hydrochloride ethanol), on the DHP-binding site in the central nervous system and various receptor sites were compared with nicardipine and diltiazem by the use of a receptor binding assay technique. NZ-105 exhibited a displacement effect against [3H]nimodipine in the rat brain DHP-binding site with a potency similar to that of nicardipine. Nicardipine also inhibited the specific binding of several other [3H]-labelled ligands to their receptor such as adrenergic alpha 1, alpha 2, beta, dopamine D1, D2, opioid mu, delta, and kappa-type receptors. Diltiazem also showed a similar inhibitory property. However, NZ-105 showed only weak inhibition against the binding to these receptors. These results suggest that Z-105 has strong affinity to the DHP-binding site in voltage-dependent calcium channels with higher specificity.