A benefit-risk assessment of extended-release oxybutynin

Potential side effects of currently available pharmacotherapies in male lower urinary tract symptoms suggestive of benign prostatic hyperplasia

INTRODUCTION

The drug classes of α1-adrenoceptor antagonists, 5α-reductase inhibitors, and phosphodiesterase type 5 inhibitors are guideline-recommended treatments of lower urinary tract symptoms suggestive of benign prostatic hyperplasia; muscarinic receptor antagonists and β3-adrenoceptor agonists are also recommended if storage symptoms are insufficiently addressed with one of the other three drug classes.

AREAS COVERED

We provide a narrative review (no formalized literature searches performed) of the tolerability of these drug classes with emphasis on the more recently introduced medications, on combination treatment, and on more lately emerging risks.

EXPERT OPINION/COMMENTARY

The tolerability profiles are distinct between drug classes but, with few exceptions, similar within a drug class. Within a drug, formulations with longer duration of action tend to have better tolerability. Efficacy gains using combination treatment at least partly come at a cost of lesser tolerability. Greater susceptibility to experience adverse events based on age, comorbidities, and comedications appears conceptually important but remains under-investigated in this therapeutic area.

Gastroretentive Technologies in Tandem with Controlled-Release Strategies: A Potent Answer to Oral Drug Bioavailability and Patient Compliance Implications

There have been many efforts to improve oral drug bioavailability and therapeutic efficacy and patient compliance. A variety of controlled-release oral delivery systems have been developed to meet these needs. Gastroretentive drug delivery technologies have the potential to achieve retention of the dosage form in the upper gastrointestinal tract (GIT) that can be sufficient to ensure complete solubilisation of the drugs in the stomach fluids, followed by subsequent absorption in the stomach or proximal small intestine. This can be beneficial for drugs that have an “absorption window” or are absorbed to a different extent in various segments of the GIT. Therefore, gastroretentive technologies in tandem with controlled-release strategies could enhance both the therapeutic efficacy of many drugs and improve patient compliance through a reduction in dosing frequency. The paper reviews different gastroretentive drug delivery technologies and controlled-release strategies that can be combined and summarises examples of formulations currently in clinical development and commercially available gastroretentive controlled-release products. The different parameters that need to be considered and monitored during formulation development for these pharmaceutical applications are highlighted.

In vitro and in vivo evaluation of a sustained-release once-a-day formulation of the novel antihypertensive drug MT-1207

Hypertension is one of the most common chronic cardiovascular disorders. Sustained-release formulations are developed to maintain drug therapeutic levels throughout the treatment of hypertension, to promote patient compliance and improve patient outcomes. We have developed and tested in in vivo trials a once-a-day tablet formulation for the novel antihypertensive drug MT-1207. The tablets based upon a hydrophilic polymer matrix underwent post-compression parameter and physicochemical characterisations, along with in vitro drug release testing. The most promising formulation containing 31% w/w HPMC K15M gave a 24-hour release of MT-1207 with an almost constant release rate up to 20 hours. Follow in in vivo studies were carried out in Beagle dogs for the optimised sustained-release tablets in comparison to immediate-release tablets. The results showed that a sustained release of MT-1207 from the new formulation was achieved with a drug t_1/2 2-2.5 times longer than the immediate-release tablets. Moreover, the AUC_0-24h values of both sustained- and immediate-release tablets were identical at the same dose of 30 mg, indicating that the same amount of drug was absorbed in each case. For treatments based upon MT-1207, this development is significant for future commercial exploitation via scale-up and further trials, and for improved patient outcomes.

A Guide to Medications Inducing Salivary Gland Dysfunction, Xerostomia, and Subjective Sialorrhea: A Systematic Review Sponsored by the World Workshop on Oral Medicine VI

BACKGROUND

Medication-induced salivary gland dysfunction (MISGD), xerostomia (sensation of oral dryness), and subjective sialorrhea cause significant morbidity and impair quality of life. However, no evidence-based lists of the medications that cause these disorders exist.

OBJECTIVE

Our objective was to compile a list of medications affecting salivary gland function and inducing xerostomia or subjective sialorrhea.

DATA SOURCES

Electronic databases were searched for relevant articles published until June 2013. Of 3867 screened records, 269 had an acceptable degree of relevance, quality of methodology, and strength of evidence. We found 56 chemical substances with a higher level of evidence and 50 with a moderate level of evidence of causing the above-mentioned disorders. At the first level of the Anatomical Therapeutic Chemical (ATC) classification system, 9 of 14 anatomical groups were represented, mainly the alimentary, cardiovascular, genitourinary, nervous, and respiratory systems. Management strategies include substitution or discontinuation of medications whenever possible, oral or systemic therapy with sialogogues, administration of saliva substitutes, and use of electro-stimulating devices.

LIMITATIONS

While xerostomia was a commonly reported outcome, objectively measured salivary flow rate was rarely reported. Moreover, xerostomia was mostly assessed as an adverse effect rather than the primary outcome of medication use. This study may not include some medications that could cause xerostomia when administered in conjunction with others or for which xerostomia as an adverse reaction has not been reported in the literature or was not detected in our search.

CONCLUSIONS

We compiled a comprehensive list of medications with documented effects on salivary gland function or symptoms that may assist practitioners in assessing patients who complain of dry mouth while taking medications. The list may also prove useful in helping practitioners anticipate adverse effects and consider alternative medications.

Impact of dose frequency on compliance and health outcomes: a literature review (1966-2006)

In order for treatments to be effective, patients must be compliant with their medication regimens. Currently, patient compliance is seen as one of the most challenging issues in treating patients with chronic diseases. Studies in which dose frequency has been changed have been reviewed across several different diseases to examine the impact of a change in dose frequency on compliance and health outcomes, as well as efficacy and tolerability. In general, reducing dose frequency may improve medication compliance and effectiveness, and reduce adverse events, while possibly reducing healthcare costs. Suggestions for future research have been presented, including a need to measure compliance with injectable formulations and a standardized definition of compliance.

Management of mixed urinary incontinence

Mixed urinary incontinence accounts for 33% of all incontinence and is the involuntary loss of urine associated with the sensation of urgency; it is also associated with exertion, sneezing or coughing. Risk factors include vaginal delivery, obesity, age and possible genetic factors. Treatment includes lifestyle changes, behavioral therapies, medication and nerve modulation. Surgery with midurethral slings can cure both stress and urge components in 40-50% of cases. Future therapies may include new medications adapting potassium and calcium channels and more widespread use of sacral neuromodulation. This review focuses on the investigation and optimal management of mixed urinary incontinence.

Oxybutynin in Detrusor Overactivity

Oxybutynin has been used for the management of detrusor overactivity for over 30 years and has withstood medical scrutiny and the test of time throughout the world. Although several agents in the class of bladder relaxants have only recently been studied, oxybutynin's effectiveness in reducing urinary frequency and urge urinary incontinence is unquestioned in the medical literature. Oxybutynin is extremely safe and effective in almost every population including children, the elderly, and those who have neurogenic bladder. With more preparations available and more dosing flexibility than any other anticholinergic medication on the market, oxybutynin remains the "gold standard" for first-line therapy for patients who have detrusor overactivity.

Treatment of the overactive bladder syndrome with muscarinic receptor antagonists - a matter of metabolites?

Antagonists of muscarinic acetylcholine receptors, such as darifenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium, are the mainstay of the treatment of the overactive bladder syndrome. Fesoterodine is a newer drug awaiting regulatory approval. We briefly review the pharmacological activity of their metabolites and discuss how active metabolites may contribute to their efficacy and tolerability in vivo. Except for trospium, and perhaps solifenacin, all of the above drugs form active metabolites, and their presence and activity need to be taken into consideration when elucidating relationships between pharmacokinetics and pharmacodynamics of these drugs. Moreover, the ratios between parent compounds and metabolites may differ depending on genotype of the metabolizing enzymes, concomitant medication, and/or drug formulation. Differential generation of active metabolites of darifenacin or tolterodine are unlikely to influence the overall clinical profile of these drugs in a major way because the active metabolites exhibit a similar pharmacological profile as the parent compound. In contrast, metabolites of oxybutynin and propiverine may behave quantitatively or even qualitatively differently from their parent compounds and this may have an impact on the overall clinical profile of these drugs. We conclude that more comprehensive studies of drug metabolites are required for an improved understanding of their clinical effects.

Anticholinergika bei überaktiver Blase

Anticholinergics act in the treatment of overactive bladder by blocking muscarinic receptors of which five subtypes exist. Their desired effects occur via M(3) receptors, but a role for M(2) receptors is being discussed. Adverse effects such as dry mouth and constipation occur also via M(3) receptors, but M(2) and M(1) receptors can mediate side effects in the heart or on cognitive function, respectively. Therefore, an M(3)-selective drug such as darifenacin could theoretically be less effective but also have fewer cardiac or central nervous side effects. However, the limited available clinical data do not support a smaller efficacy or better general tolerability. The lack of adverse effects on cognitive function is well documented for darifenacin, but it cannot yet be determined definitively whether this discriminates it from other modern anticholinergics.

Extended-release formulations of oxybutynin and tolterodine exhibit similar central nervous system tolerability profiles: a subanalysis of data from the OPERA trial

OBJECTIVE

This study was undertaken to compare the central nervous system (CNS) tolerability profiles of the extended-release formulations of oxybutynin chloride and tolterodine tartrate in the treatment of women with overactive bladder (OAB), as observed in the OPERA (Overactive bladder: Performance of Extended Release Agents) trial.

STUDY DESIGN

The OPERA trial was a randomized, double-blind, active-control comparison of the efficacy and safety of extended-release oxybutynin (10 mg/d) and extended-release tolterodine (4 mg/d) given to 790 women with OAB for 12 weeks. The incidence of reported CNS events was compared between the treatment groups by using the Fisher exact test.

RESULTS

The incidence of CNS adverse events was 9% and 8% for the oxybutynin and tolterodine treatment groups, respectively. The difference between groups was not statistically significant. All reported CNS adverse events were rated as mild or moderate in severity. There were no serious treatment-related adverse events in either group, and discontinuation because of a CNS adverse event was infrequent.

CONCLUSION

The extended-release formulations of oxybutynin and tolterodine were observed to be associated with a similar low incidence of CNS adverse events, which were mostly mild or moderate in severity.

Effect of controlled-release delivery on the pharmacokinetics of oxybutynin at different dosages: severity-dependent treatment of the overactive bladder

OBJECTIVE

To assess the pharmacokinetics of a controlled-release formulation of oxybutynin (OROS-O, ALZA Corp., Mountain View, CA) at different dosages, compared with immediate-release oxybutynin (IR-O), and to determine the pharmacodynamic properties in the severity-dependent reduction of urge urinary incontinence (UUI).

PATIENTS AND METHODS

In all, 105 patients were enrolled in this multicentre, randomized, double-blind study. Individual dose titration was used to assess the minimum effective, maximum tolerated or maximum allowed dose of either OROS-O or IR-O. Blood samples were collected during maintenance therapy with frequent sampling to analyse for R-oxybutynin and R-desethyloxybutynin concentrations. Pre-dose plasma levels before dosing were obtained as the minimum concentrations achieved at steady state during the dosing regimen. In parallel, UUI episodes were assessed at baseline and during maintenance therapy at the final dose level.

RESULTS

For both IR-O and OROS-O, initial R-oxybutynin plasma concentrations increased in a dose-dependent fashion. For comparable dosages pre-dose plasma levels were higher for OROS-O than IR-O. After one dose of IR-O plasma concentrations peaked at approximately 27-fold after 1 h and decreased to baseline levels within 4-8 h. In contrast, plasma concentrations of R-oxybutynin remained constant for up to 24 h after taking OROS-O at all doses. The overall percentage reduction in weekly UUI episodes was 84% (to 4.8 episodes) and 88% (to 3.1 episodes) for OROS-O and IR-O, respectively (P < 0.05). Patients who titrated to final dose levels of 10, 15 and 20 mg OROS-O differed in their weekly UUI episodes at baseline (14.5, 30.3 and 42.0). Because of individual dose titration, UUI episodes/week were profoundly reduced at all applied doses (1.9-2.0, respectively). Fewer patients reported moderate to severe dry mouth with OROS-O than with IR-O (25% vs 46%, P < 0.05).

CONCLUSION

The pharmacokinetics of OROS-O are proportional to dose, with minimal fluctuations between peak and trough concentrations, as associated with IR-O. In clinical practice OROS-O may thus facilitate the highly effective severity-dependent treatment of UUI with flexible dose adaptations based on the patients' needs.

Evaluating the economic consequences of early antidepressant treatment discontinuation: a comparison between controlled-release and immediate-release paroxetine

INTRODUCTION

Early antidepressant discontinuation has been linked to significant clinical and economic consequences. Clinical practice guidelines suggest that treatment should last for at least 3 to 9 months into the continuation phase; however, 30% of patients discontinue therapy within 30 days, and over 40% discontinue therapy within 90 days of initiation, primarily due to adverse events. Clinical trials have shown that controlled-release (CR) paroxetine has a favorable tolerability profile when compared to immediate-release (IR) paroxetine, which may result in lower discontinuation rates and improved economic outcomes. This is the first study to directly compare treatment discontinuation rates and health care expenditures of a CR selective serotonin reuptake inhibitors with its IR counterpart.

METHODS

This matched retrospective study used claims from a national managed care database to assess differences in discontinuation rates and health care expenditures between paroxetine CR and IR for treating depression and/or anxiety. Discontinuation was assessed by survival analysis, and health care expenditure was assessed using average monthly medical and pharmacy charges.

RESULTS

There were 1275 paroxetine CR patients and 2550 paroxetine IR patients matched in the analysis. At 90 days, 62% of paroxetine CR patients continued therapy versus 56% of paroxetine IR patients. At 180 days, 51% of paroxetine CR patients continued therapy versus 42% of paroxetine IR patients. When evaluating all medical charges, paroxetine CR patients incurred US 119 dollars less per month than paroxetine IR patients (P = 0.054).

CONCLUSIONS

Patients receiving paroxetine CR remained on therapy longer than patients on paroxetine IR, which resulted in lower total monthly medical costs for patients receiving paroxetine CR. Differences in costs were primarily driven by reduction in hospitalization expenditures.