Effect of time interval between food and drug ingestion on the absorption of oxybutynin from a controlled-release tablet

A short review of drug-food interactions of medicines treating overactive bladder syndrome

Background Overactive bladder syndrome is a condition where one or more of the symptoms such as pollakiuria, urgent need to urinate, nocturia and urinary incontinence is observed. Its prevalence ranges between 7 and 27 % in men and 9–43 % in women. The role of a pharmacist is to educate the patient on medications administration scheme, and drug interactions with particular food or food components. Aim of the review To assess a potential impact of food and fruit juice on the pharmacokinetic and therapeutic effects of medications used in treating overactive bladder syndrome. This information will enhance pharmaceutical care and is vital and helpful for pharmacists counseling their patients. Method In order to gather information on interactions of medications employed in bladder dysfunctions, the English language reports published in the PubMed, Embase, Cochrane and CINAHL database over the years 1996–2015 were studied. Additionally, other resources, namely drugs.com, Medscape, UpToDate, Micromedex, Medical Letter, as well as Stockley Drugs Interaction electronic publication were included in the study. The analysis also covered product data sheets for particular medicinal products. Results Meals and the consumption of grapefruit juice were found to exert a diversified effect on the pharmacokinetics of drugs employed in overactive bladder syndrome therapy. Neither tolterodine, nor mirabegron interact with food and citrus fruit juice, whereas darifenacin, fesoterodine, oxybutynin and solifenacin do interact with grapefruit and others citrus fruit juice. The effects of such interactions may potentially be negative to patients. Trospium absorption is significantly decreased by food. Conclusion For selected medicines used in treating bladder dysfunctions food and grapefruit juice consumption may significantly affect efficacy and safety of the therapy. All information on the topic is likely to enhance the quality of pharmaceutical care.

Oral osmotically driven systems: 30 years of development and clinical use

The number of marketed oral osmotically driven systems (OODS) has doubled in the last 10 years. The main clinical benefits of OODS are their ability to improve treatment tolerability and patient compliance. These advantages are mainly driven by the capacity to deliver drugs in a sustained manner, independent of the drug chemical properties, of the patient's physiological factors or concomitant food intake. However, access to these technologies has been restricted by the crowded patent landscape and manufacturing challenges. In this review article, we intend to give an overview of the OODS development in the last 30 years, detailing the technologies, specific products and their clinical use. General guidance on technology selection is described in light of the recent advances in the field. The clinical performance of these technologies is also discussed, with a focus on food effects and the in vivo-in vitro correlation. Special attention is paid to safety given the controversial case study of Osmosin. Overall, oral osmotically driven systems appear to be a promising technology for product life-cycle strategies.

Adsorptive stripping voltammetric behavior and determination of anticholinergic agent oxybutynin chloride on a mercury electrode

Oxybutynin chloride is an antispasmodic, anticholinergic agent indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency. Its electrochemical behavior in phosphate buffers of pH range 2-10 at a hanging mercury drop electrode has been investigated using cyclic voltammetry, differential pulse cathodic adsorptive stripping voltammetry (DPCAdSV), and squarewave cathodic adsorptive stripping voltammetry (SWCAdSV). Voltammograms of the drug in phosphate buffer of pH 2-10 exhibited a single two-electron wave and it may be attributed to the reduction of the C[triple bond]C center. Based on the high adsorptive character of oxybutynin chloride onto the mercury electrode, a validated direct squarewave cathodic adsorptive stripping voltammetric and differential pulse cathodic adsorptive stripping voltammetric procedure has been developed for the determination of drug in bulk form and pharmaceutical formulation. The proposed SWCAdS and DPCAdS voltammetric methods allow quantitation over the range 1-18 and 1-17.6 microg mL(-1) with detection limits of 0.1 and 0.23 microg mL(-1), respectively. Precision and accuracy were also checked and were within the limits.

Effect of the proton pump inhibitor omeprazole on the pharmacokinetics of extended-release formulations of oxybutynin and tolterodine

This study assessed the effect of the proton pump inhibitor omeprazole on the bioavailability of the extended-release formulations of oxybutynin and tolterodine. Forty-four healthy volunteers received each of 4 treatments in a 4-period crossover design. The treatments consisted of osmotically controlled extended-release oxybutynin chloride tablets at 10 mg/d or extended-release tolterodine tartrate capsules at 4 mg/d, with and without preceding treatment with 20 mg omeprazole daily for 4 days. Blood samples collected predose and at scheduled time points for 36 hours postdose were analyzed for oxybutynin and its active metabolite, N-desethyloxybutynin, or tolterodine and its active 5-hydroxymethyl metabolite, as appropriate. The AUCinfinity ratios for oxybutynin and its metabolite with and without prior omeprazole fell within the 80% to 125% range (accepted as the criterion for bioequivalence), as did those for tolterodine and its active moiety. The peak concentration ratios for oxybutynin and metabolite also conformed to this range; those for tolterodine did not. Increasing gastric pH with omeprazole does not substantially alter the pharmacokinetic properties of extended-release oxybutynin but may alter those of extended-release tolterodine.

Rapid and selective UV spectrophotometric and RP-HPLC methods for dissolution studies of oxybutynin immediate-release and controlled-release formulations

A new UV spectrophotometric method and a reversed-phase HPLC method were developed for quantitative evaluation of oxybutynin hydrochloride (OXB) formulations. Determination of OXB by UV spectroscopic method was based on complexation of OXB with picric acid to form picrate, which was extracted to chloroform. The picrate complex showed quantifiable absorbance at 344nm. Chromatography was carried out at 25 degrees C on a 4.6mm x 250mm 5microm cyano column that contained USP packing L10 with water:methanol:acetonitrile::48:12:40 (v/v), as mobile phase. UV detector was set at 203nm. Both methods were found to be selective, linear, accurate and precise in the specified ranges. The LOD and LOQ of HPLC method were 0.5 and 1.65microg/ml, respectively. Intra-day and inter-day variability for both methods were <2% RSD. These methods were successfully used for quantification of OXB in drug-release studies from immediate-release tablets and controlled-release (CR) formulations.

Clinical pharmacokinetics of drugs used to treat urge incontinence

Urge incontinence (also known as overactive bladder) is a common form of urinary incontinence, occurring alone or as a component of mixed urinary incontinence, frequently together with stress incontinence. Because of the pathophysiology of urge incontinence, anticholinergic/antispasmodic agents form the cornerstone of therapy. Unfortunately, the pharmacological activity of these agents is not limited to the urinary tract, leading to systemic adverse effects that often promote nonadherence. Although the pharmacokinetics of flavoxate, propantheline, scopolamine, imipramine/desipramine, trospium chloride and propiverine are also reviewed here, only for oxybutynin and tolterodine are there adequate efficacy/tolerability data to support their use in urge incontinence. Oxybutynin is poorly absorbed orally (2-11% for the immediate-release tablet formulation). Controlled-release oral formulations significantly prolong the time to peak plasma concentration and reduce the degree of fluctuation around the average concentration. Significant absorption occurs after intravesical (bladder) and transdermal administration, although concentrations of the active N-desethyl metabolite are lower after transdermal compared with oral administration, possibly improving tolerability. Food has been found to significantly affect the absorption of one of the controlled-release formulations of oxybutynin, enhancing the rate of drug release. Oxybutynin is extensively metabolised, principally via N-demethylation mediated by the cytochrome P450 (CYP) 3A isozyme. The pharmacokinetics of tolterodine are dependent in large part on the pharmacogenomics of the CYP2D6 and 3A4 isozymes. In an unselected population, oral bioavailability of tolterodine ranges from 10% to 74% (mean 33%) whereas in CYP2D6 extensive metabolisers and poor metabolisers mean bioavailabilities are 26% and 91%, respectively. Tolterodine is metabolised via CYP2D6 to the active metabolite 5-hydroxymethyl-tolterodine and via CYP3A to N-dealkylated metabolites. Urinary excretion of parent compound plays a minor role in drug disposition. Drug effect is based upon the unbound concentration of the so-called 'active moiety' (sum of tolterodine + 5-hydroxymethyl-tolterodine). Terminal disposition half-lives of tolterodine and 5-hydroxymethyl-tolterodine (in CYP2D6 extensive metabolisers) are 2-3 and 3-4 hours, respectively. Coadministration of antacid essentially converts the extended-release formulation into an immediate-release formulation. Knowledge of the pharmacokinetics of these agents may improve the treatment of urge incontinence by allowing the identification of individuals at high risk for toxicity with 'usual' dosages. In addition, the use of alternative formulations (controlled-release oral, transdermal) may also facilitate adherence, not only by reducing the frequency of drug administration but also by enhancing tolerability by altering the proportions of parent compound and active metabolite in the blood.

Sensitive determination of oxybutynin and desethyloxybutynin in dog plasma by LC-ESI/MS/MS

A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry (LC-MS/MS) was developed for the quantification of oxybutynin and desethyloxybutynin in dog plasma. Diazepam was used as internal standard, with plasma sample extracted using n-hexane and back-extracted using hydrochloric acid. A centrifuged lower layer (aqueous layer) was injected into a C(18) XTerra MS column (2.1 x 30 mm(2)) with 3.5 microm particle size. The analytical column lasted for at least 500 injections. The mobile phase was composed of 90% methanol, with flow rate at 200 microl/min. The mass spectrometer was operated in positive ion mode using electrospray ionization. Nitrogen was used as the nebulizer gas and argon was used as the collision gas. Using MS/MS with multiple reaction monitoring (MRM) mode, oxybutynin and desethyloxybutynin were detected without severe interferences from plasma matrix. Oxybutynin produced a protonated precursor ion ([M+H](+)) at m/z 358 and a corresponding product ion at m/z 142. Desethyloxybutynin produced a protonated precursor ion ([M+H](+)) at m/z 330 and a corresponding product ion at m/z 96. And internal standard (diazepam) produced a protonated precursor ion ([M+H](+)) at m/z 285 and a corresponding product ion at m/z 193. Detection of oxybutynin and desethyloxybutynin in dog plasma were accurate and precise, with detection limit at 0.1 ng/ml. This method has been successfully applied to a study of oxybutynin and desethyloxybutynin in dog plasma.

Oxybutynin chloride: alterations in drug delivery and improved therapeutic index

Oxybutynin chloride (Ditropan, Alza) is widely regarded as the most efficient antimuscarinic agent for the treatment of bladder detrusor dysfunction resulting in urinary urgency, frequency and urge incontinence. Oxybutynin metabolism occurs primarily in the proximal gastrointestinal tract and the hepatic circulation and is mediated by the cytochrome P450 3A4 isozyme. The major degradation products are desethyloxybutynin, which possesses pharmacological activity, and phenylcyclohexylglycolic acid, which is metabolically inert. A major limitation to long-term compliance with immediate-release oxybutynin remains the necessity for twice- or thrice-daily dosing regimens to provide sustained pharmacological efficacy. Side effects induced by cytochrome P450 metabolism of oxybutynin into the primary metabolite desethyloxybutynin within the gut wall substantially affect the tolerability of the compound within the individual. The oral osmotic delivery system provides unique advantages for drug delivery and substantially alters the tolerability profile of the oxybutynin chloride compound. This extended-release formulation consists of a two component core encapsulated by a semi-permeable membrane. The osmotic gradient between the surrounding environment and the inner core of the delivery system remains constant and water absorption within the capsule is controlled by the semipermeable membrane causing a controlled release of drug, which is sustained over 24 h. Herein are reviewed the various pre- and post-approval trials which have documented the overall therapeutic index of the oral osmotic oxybutynin (Ortho-McNeil Pharmaceuticals). Subsequent post-market surveillance issues are reviewed as are new developments in oxybutynin delivery.

Effect of OROS controlled-release delivery on the pharmacokinetics and pharmacodynamics of oxybutynin chloride

Aims : Dry mouth is a common side-effect seen with immediate-release oxybutynin (IR-Oxy). Ditropan XL [(Oxy-XL), a controlled-release formulation of oxybutynin chloride, is a once-daily oral dosage form that incorporates the OROS technology. Dry mouth as the pharmacodynamic measure was compared between Oxy-XL and IR-Oxy administration. The steady state stereospecific pharmacokinetics were also established for the two formulations and the kinetic-dynamic relationship of oxybutynin was examined.

METHODS

This was a randomized, repeated-dose, double-blind, two-treatment, two-period, crossover study. After a baseline assessment day, volunteers were randomly assigned to one of two treatment sequences and received 4 days of each treatment with a washout period of 7 days between treatments. The treatments were: 1) Oxy-XL 10 mg in the morning and placebo 8 h later, and 2) IR-Oxy 5 mg in the morning and again 8 h later. Volunteers assessed dry mouth severity subjectively using a 100 mm visual analogue scale, VAS (Baseline, treatment days 1 and 4) and objectively by collecting saliva (Baseline and treatment day 4) before dosing and every hour after the morning dose for approximately 16 h. Several blood samples were collected during each treatment, with frequent sampling on day 4 to analyse for plasma R- and S-oxybutynin and R- and S-desethyloxybutynin concentrations.

RESULTS

Relatively constant plasma concentrations of oxybutynin and its metabolite were seen over 24 h following Oxy-XL administration with the degree of fluctuation being much lower (P = 0.001; 66% to 81% reduction for the various analytes) than IR-Oxy. Compared with IR-Oxy, Oxy-XL yielded higher (131% and 158% for the R- and S-isomer, respectively) oxybutynin and lower (62% and 78% for the R- and S-isomer, respectively) desethyloxybutynin bioavailability, suggesting reduced first-pass metabolism. Saliva output (area under the effect curve) was significantly higher [P = 0.001; 37% (95% confidence interval: 24, 51%)] with Oxy-XL than with IR-Oxy and, accordingly, dry mouth severity (VAS) integrated over the day was significantly lower with Oxy-XL. The decrease in saliva output and the consequent increase in dry mouth severity correlated with the metabolite R-desethyloxybutynin concentration, and no apparent relationship was observed with the R-oxybutynin concentration. This suggests that the metabolite may contribute to the dry mouth. Therefore, the reduction in metabolite exposure with Oxy-XL may be a possible explanation for the observed decrease in dry mouth severity with OXY-XL compared with IR-Oxy.

CONCLUSIONS

Oxy-XL maintains relatively constant plasma drug and metabolite concentrations and minimizes first-pass metabolism of oxybutynin. The metabolite appears to contribute to dry mouth associated with oxybutynin, and following Oxy-XL metabolite exposure is reduced compared with IR-Oxy. Consequently less dry mouth was observed with Oxy-XL as compared with IR-Oxy.

Lack of effect of food on the pharmacokinetics of an extended-release oxybutynin formulation

The effect of food on the pharmacokinetics of 15 mg oxybutynin XL was evaluated in a single-dose, randomized, crossover, open-label study in healthy volunteers. A validated, stereospecific, high-performance liquid chromatography assay was used to simultaneously determine the plasma concentrations of R- and S-oxybutynin and active metabolite R- and S-desethyloxybutynin. The mean AUC and Cmax values for each of the four analytes in the fed treatment were within +/- 20% of the fasting treatment values. The 90% confidence intervals for the treatment ratios (fed/fasted) for log-transformed Cmax and AUCinf values for the drug isomers and AUCinf values for the metabolite isomers were all within the 80% to 125% range. Only the ranges for the Cmax values for R- and S-desethyloxybutynin were slightly wider but were well within the 70% to 143% criteria recommended for Cmax when comparing effect of food. Lack of effect of food on oxybutynin XL is consistent with the previous observation that the osmotically controlled formulations are nearly insensitive to the gastrointestinal environment, including food. Oxybutynin XL was well tolerated, and the safety results were comparable whether administered alone or with food. In conclusion, oxybutynin XL administration does not require any caution to be exercised regarding food.

Differences in the effects of urinary incontinence agents S-oxybutynin and terodiline on cardiac K(+) currents and action potentials

1. The cardiac electrophysiological effects of S-oxybutynin, a single-enantiomer drug under evaluation for the management of urinary incontinence, have been investigated and compared with those of terodiline, an incontinence agent withdrawn following reports of QT lengthening and ventricular tachyarrhythmia. Membrane currents were recorded from whole-cell configured guinea-pig and rabbit ventricular myocytes, and action potentials were recorded from guinea-pig and rabbit papillary muscles. 2. L-type Ca(2+) current (I:(Ca,L)), rapidly-activating K(+) current (I:(Kr)) and slowly-activating K(+) current (I:(Ks)) were unaffected by submicromolar S-oxybutynin and inhibited by higher concentrations; IC(50) values were 17.8 microM for I:(Ca,L), 12 microM for I:(Kr), and 41 microM for I:(Ks). Terodiline IC(50) values were somewhat lower for I:(Ca,L) (15.2 microM) and I:(Ks) (30 microM), but 24 fold lower in the case of I:(Kr) (0.5 microM). 3. The durations of action potentials in guinea-pig and rabbit papillary muscles driven at 1 Hz were unaffected or moderately shortened by 0.1 - 100 microM S-oxybutynin, but lengthened by terodiline. Terodiline (< or =10 microM) also depressed maximal upstroke velocity. 4. The action potential plateau shortened by an average of 23% when control rabbit papillary muscles were driven at 0.4 Hz instead of 1 Hz. Plateau shortening was significantly smaller in the presence of drugs (30 microM S-oxybutynin, 3 and 30 microM terodiline), suggesting that they suppress the transient outward current (I:(to)) involved in rate-dependent shortening. In experiments on rabbit ventricular myocytes, 3 and 30 microM S-oxybutynin inhibited I:(to) by 9+/-2% and 35+/-3%, respectively, whereas 3 and 30 microM terodiline inhibited the current by 31+/-3% and 87+/-3%, respectively. 5. The results indicate that S-oxybutynin has relatively weak non-specific effects on cardiac ion channels, and that clinically relevant submicromolar concentrations are unlikely to have terodiline-like proarrhythmic actions on the myocardium.

Analysis of the electrophysiologic effects of short-term oxybutynin on guinea pig and rabbit ventricular cells

The objective of this study was to investigate the cardioactive properties of oxybutynin, a drug that is widely prescribed for management of voiding dysfunction. Membrane currents were recorded from whole-cell-configured guinea pig ventricular myocytes, and action potentials were recorded from guinea pig and rabbit papillary muscles. L-type Ca2+ current (I(Ca),L), inward-rectifier K+ current (I(K1)), and delayed-rectifier K+ current (I(K)) were unaffected by < or = 1 microM oxybutynin, and inhibited by higher concentrations. The concentrations that reduced the currents to one-half of predrug control amplitude (K0.5) were as follows: 1(Ca),L, 16.1 microM, I(K1), 18.2 microM, rapidly activating I(K)(I(Kr)), 11.4 microM, and slowly activating I(K)(I(Ks)), 28.7 microM. Action-potential durations at 20 and 90% repolarization (APD20, APD90) were unaffected by oxybutynin < or =3 microM in guinea pig papillary muscles driven at 1 Hz; higher concentrations selectively shortened the APD20 by as much as 25% (100 microM), and caused moderate reductions in maximal upstroke velocity. Changes in the action potentials of rabbit papillary muscles were even smaller than in the guinea pig muscles. Because the peak therapeutic plasma concentration of oxybutynin is in the 0.01-0.1 microM range, the results suggest that the drug is highly unlikely to have adverse effects on cardiac electrical activity.