Food increases the bioavailability of tolterodine but not effective exposure

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.

Pharmacologically active drug metabolites: impact on drug discovery and pharmacotherapy

Metabolism represents the most prevalent mechanism for drug clearance. Many drugs are converted to metabolites that can retain the intrinsic affinity of the parent drug for the pharmacological target. Drug metabolism redox reactions such as heteroatom dealkylations, hydroxylations, heteroatom oxygenations, reductions, and dehydrogenations can yield active metabolites, and in rare cases even conjugation reactions can yield an active metabolite. To understand the contribution of an active metabolite to efficacy relative to the contribution of the parent drug, the target affinity, functional activity, plasma protein binding, membrane permeability, and pharmacokinetics of the active metabolite and parent drug must be known. Underlying pharmacokinetic principles and clearance concepts are used to describe the dispositional behavior of metabolites in vivo. A method to rapidly identify active metabolites in drug research is described. Finally, over 100 examples of drugs with active metabolites are discussed with regard to the importance of the metabolite(s) in efficacy and safety.

Pharmacokinetics and toxicity of antimuscarinic drugs for overactive bladder treatment in females

INTRODUCTION

Antimuscarinics (AMs) are the mainstay of pharmacological treatment of overactive bladder (OAB), a symptom complex defined by the presence of urinary urgency, usually associated with frequency and nocturia, with or without urgency urinary incontinence. The AMs used to treat OAB differ in their pharmacological profiles, which may affect their potential for causing adverse effects (AEs).

AREAS COVERED

The present article aims to review the literature about pharmacokinetics (PK) of the different AMs used in the treatment of OAB. Furthermore, the AEs related to the use of these drugs and their incidence are presented. This systematic review is based on material searched and obtained via Medline, Pubmed and EMBASE up to March 2012 using the search terms "adverse events, pharmacokinetics, tolerability" in combination with "darifenacin, fesoterodine, imidafenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium."

EXPERT OPINION

Antimuscarinics are the first-line pharmacological treatment for OAB. Despite the development of new molecules that improve their efficacy/safety profile, there are some drugs that are pharmacokinetically more appropriate to be prescribed in specific populations such as patients with neurological disease or the elderly. Moreover, research should be encouraged in evaluating antimuscarinics in conjunction with other drugs such as estrogens or beta-agonists. The identification of prognostic criteria for pharmacological therapy would be helpful.

Tolterodine for Treatment of Overactive Bladder

Tolterodine was developed as an antimuscarinic agent specifically for the treatment of overactive bladder. Initial in vivo studies demonstrated a functional selectivity for the muscarinic receptors in the urinary bladder over the salivary glands, and subsequent clinical trials showed an overall superior tolerability profile compared with other drugs in the same class (ie, oxybutynin). With immediate- and extended-release formulations and sustained clinical efficacy during long-term treatment, tolterodine gas become an important treatment option for the symptoms of overactive bladder.

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.

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.

Food does not influence the pharmacokinetics of a new extended release formulation of tolterodine for once daily treatment of patients with overactive bladder

OBJECTIVE

To determine whether food intake influences the pharmacokinetics of a new, once daily, extended release (ER) capsule formulation of tolterodine in healthy volunteers, and to compare its bioavailability with that of the existing immediate release (IR) tablet.

DESIGN

Open, randomised, 3-way crossover trial.

PARTICIPANTS

17 healthy volunteers (3 females, 14 males) aged between 19 and 50 years. With the exception of 1 male volunteer, all participants were classified as extensive metabolisers by cytochrome P450 2D6 genotyping.

METHODS

Volunteers received single oral doses of tolterodine L-tartrate ER 8 mg (2 x 4 mg capsules) on an empty stomach or with a standardised high-fat breakfast. Reference therapy comprised tolterodine L-tartrate IR 4 mg (2 x 2 mg tablets), administered in the fasting state. Serum concentrations of tolterodine, its active 5-hydroxymethyl metabolite (5-HM) and the active moiety (sum of unbound tolterodine + 5-HM) were measured for up to 72 hours post-dose. Safety endpoints were also determined.

RESULTS

No effect of food on the bioavailability of tolterodine ER capsules was apparent and there was no sign of dose-dumping with meals. The geometric mean fed:fasting ratio of area under the serum concentration-time curve to infinity (AUCinfinity) of the active moiety, for all volunteers combined, was 0.95 (90% confidence interval 0.88 to 1.03). Equivalence with respect to AUCinfinity (dose-corrected) was also found for the ER capsule compared with the IR tablet, although uncorrected maximum serum concentrations were around 50% lower despite the fact that the capsule dose was twice as high. Seven volunteers reported adverse events, predominantly headache. No volunteer reported dry mouth. Overall, there were no safety concerns.

CONCLUSIONS

The new ER formulation of tolterodine shows no pharmacokinetic interaction with food. On the basis of these results, patients with overactive bladder may, therefore, be advised to take the drug without regard to the timing of meals, maximising convenience during therapy.

Tolterodine: a review of its use in the treatment of overactive bladder

Tolterodine is a competitive muscarinic receptor antagonist that shows in vivo selectivity for the bladder over the salivary glands compared with oxybutinin. Results of randomised double-blind placebo-controlled studies indicate that tolterodine 4 mg/day (administered as immediate-release tablets 2mg twice daily or extended-release capsules 4mg daily) is superior to placebo in improving micturition diary variables in patients with overactive bladder. Moreover, tolterodine 2mg twice daily is as effective as oxybutynin 5mg 3 times daily. Maximum treatment effects with both drugs occurred after 5 to 8 weeks of treatment and improvements were maintained during long term treatment for up to 24 months. In a pooled analysis of four 12-week studies, equivalent and significant reductions in micturition frequency (-2.3 and -2.0 vs -1.4, p < 0.001) and the incidence of urge incontinence episodes (-1.6 and -1.8 vs -1.1, p < 0.05) were reported for tolterodine 2mg twice daily and oxybutynin 5mg 3 times daily compared with placebo. Functional bladder capacity was also significantly increased. Improvements in patient perceptions of their urgency symptoms and of problems caused by their bladder condition were significantly greater during treatment with tolterodine than with placebo. Tolterodine was generally well tolerated in clinical trials of up to 24 months' duration. Dry mouth was the most frequent adverse event. The incidence (40 vs 78%, p < 0.001) and intensity of this event was lower with tolterodine 2mg twice daily than oxybutynin 5mg 3 times daily. Additionally, a 23% lower incidence of dry mouth was reported with once daily extended-release tolterodine capsules than with twice daily immediate-release tablets (p < 0.02). The incidence of adverse CNS events with tolterodine was low and similar to that of placebo. Tolterodine was well tolerated in elderly patients and no serious tolerability concerns were identified.

CONCLUSION

Tolterodine is the first antimuscarinic agent to specifically developed for the treatment of overactive bladder. The functional selectivity of tolterodine for the bladder translates into good efficacy and tolerability in patients, including the elderly, with overactive bladder. Tolterodine is as effective as oxybutynin in improving micturition diary variables but is associated with a significantly lower incidence and intensity of dry mouth. This favourable tolerability profile, together with sustained clinical efficacy during long term treatment, places tolterodine as valuable treatment for the symptoms of overactive bladder.

Multiple dose pharmacokinetics of a new once daily extended release tolterodine formulation versus immediate release tolterodine

OBJECTIVE

To determine the multiple dose pharmacokinetics of a new extended release (ER) capsule formulation of tolterodine, compared with the existing immediate release (IR) tablet, in healthy volunteers.

DESIGN

Nonblind, randomised, 2-way crossover trial.

PARTICIPANTS

19 healthy volunteers (7 females, 12 males), mean age 33 years (range 18 to 55 years). Prior to the study, all volunteers were classified as either extensive or poor metabolisers by cytochrome P450 2D6 genotyping.

METHODS

Volunteers received tolterodine ER 4mg once daily or tolterodine IR 2mg twice daily for 6 days (all doses given as the L-tartrate salt). A washout period of 7 days separated the 2 treatments. Serum concentrations of tolterodine, its active 5-hydroxymethyl metabolite (5-HM) and the active moiety (extensive metabolisers: sum of unbound tolterodine + 5-HM; poor metabolisers: unbound tolterodine) were measured for up to 48 hours post-dose on day 6 (steady state). Tolerability was also determined.

RESULTS

17 volunteers (13 extensive metabolisers, 4 poor metabolisers) completed the study and were evaluable for both treatment periods. The 90% confidence interval for the geometric mean ratio of area under the serum concentration-time curve to 24 hours (AUC24) of the active moiety, for all volunteers combined, indicated equivalence for the 2 formulations. Pooled analysis also demonstrated that the peak serum concentration (Cmax) of the active moiety following administration of tolterodine ER was around 75% of that observed for the IR tablet, whereas the trough concentration was around 1.5-fold higher. Overall, the pharmacokinetics of tolterodine (irrespective of genotype) and 5-HM (extensive metabolisers only) were consistent with sustained drug release over 24 hours. Tolterodine ER was well tolerated.

CONCLUSIONS

The new once daily ER formulation of tolterodine 4mg shows pharmacokinetic equivalence (AUC24) to the existing IR tablet given at a dose of 2mg twice daily. Findings of lower Cmax for tolterodine ER may explain the significantly lower rate of dry mouth subsequently observed in patients with overactive bladder.