Population pharmacokinetics of the 5-hydroxymethyl metabolite of tolterodine after administration of fesoterodine sustained release tablet in western and east Asian populations

An Investigation in the Comparability of the Exposure and Recommended Dose of Selected Pfizer Drugs in East Asian Countries: Is Mutual Usage of Clinical Data Among East Asian Countries Feasible?

The current regulatory path for new drug registration in East Asian countries has led to significant delay of the new medicines in these countries. A unified regulatory path and allowance of mutual usage of clinical data in East Asian countries would lead to cost saving in drug development and expedite the new drug registration in these countries. The objectives of the present analysis are to compare the approval dates of a selection of products developed by Pfizer in the United States and East Asian countries (China, Japan, Korea) and compare the pharmacokinetics and recommended doses of these products in East Asian countries. Eighteen products (20 drugs, 2 products with 2 combination drugs) with exposure data available in at least 2 of the 3 East Asian countries across different therapeutic areas were included in the analyses. The results showed that most products had delayed approval in East Asian countries (up to 8 years) after US or EU approval. No distinct differences were observed in the drug exposure and recommended doses for the selected products in East Asian countries. These results together with literature data of genetic similarity of the East Asian populations support the mutual usage of the clinical data in the East Asian countries for expedited regulatory submission and approval.

Population Pharmacokinetic and Pharmacodynamic Modeling of Fesoterodine in Pediatric Patients with Neurogenic Detrusor Overactivity

BACKGROUND AND OBJECTIVE

Fesoterodine is a muscarinic receptor antagonist approved for the treatment of overactive bladder (OAB) in adults and neurogenic detrusor overactivity (NDO) in pediatric patients. This work aimed to characterize the population pharmacokinetics of 5-hydroxymethyl tolterodine (5-HMT, the active metabolite of fesoterodine) and its pharmacokinetic/pharmacodynamic relationship in pediatric patients with OAB or NDO following administration of fesoterodine.

METHODS

5-HMT plasma concentrations from 142 participants of age ≥ 6 years were analyzed, and a nonlinear mixed-effects model was developed. Weight-based simulations of 5-HMT exposure and maximum cystometric capacity (MCC) were conducted using the final models.

RESULTS

A one-compartment model with first-order absorption and a lag time, which included the effects of body weight, sex, cytochrome (CYP) 2D6 metabolizer status and fesoterodine formulation on pharmacokinetic parameters, best described the 5-HMT pharmacokinetics. An Emax model described the exposure-response relationship adequately. The median maximum concentration at steady state for pediatric patients weighing 25-35 kg and receiving 8 mg once daily (QD) was estimated to be 2.45 times greater than that in adults receiving 8 mg QD. Furthermore, simulation results showed dosing with fesoterodine 4 mg QD to pediatric patients weighing 25-35 kg and 8 mg QD to pediatric patients weighing >35 kg would achieve adequate exposure to demonstrate a clinically meaningful change from baseline (CFB) MCC.

CONCLUSIONS

Population models were developed for 5-HMT and MCC in pediatric patients. Weight-based simulations indicated that 4 mg QD for pediatric patients weighing 25-35 kg and 8 mg QD for those weighing > 35 kg provided similar exposures to those in adults following 8 mg QD and a clinically meaningful CFB MCC.

CLINICAL TRIAL NUMBERS

NCT00857896, NCT01557244.

Randomized, open-label, tolterodine-controlled, comparative study of the novel antimuscarinic agent imidafenacin in patients with overactive bladder

BACKGROUND

The role of the selective antimuscarinic imidafenacin in Caucasian patients with overactive bladder (OAB) has not been previously assessed.

OBJECTIVE

To evaluate the safety and efficacy of imidafenacin 0.2 mg vs tolterodine 4 mg per day in patients with OAB.

DESIGN SETTING AND PARTICIPANTS

This study was a randomized, open-label, tolterodine-controlled, comparative multicenter trial of 300 randomized patients with OAB symptoms for 12 weeks with full analysis of 289 patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Based on 5-day bladder diaries, the primary efficacy endpoint was the change in the mean number of micturitions per day. The secondary endpoints were the change in the mean incontinence episodes, voiding frequency, the OAB Awareness Tool score, and the European Quality of Life Questionnaire (EQ-5D) score. The superiority of tolterodine over imidafenacin in the mean number of micturitions/24 hours was the null hypothesis.

RESULTS AND LIMITATION

The median age was 46.6 years, and 82% of patients were female. After treatment, the change in the mean number of incontinence episodes was -2.1 ± 2.2 in the imidafenacin group and -1.9 ± 1.8 in the tolterodine group (P = .001). The change in the mean number of daytime incontinence episodes was -1.7 ± 1.7 and -1.5 ± 1.4 ( P = .01). The OAB Awareness Tool score decreased by 14.2 ± 8.5 and 14.5 ± 8.0, respectively ( P = 0.5). Most adverse events were mild and resolved without treatment.

CONCLUSIONS

The clinical efficacy and safety of imidafenacin are not inferior to those of tolterodine for the treatment of Caucasian patients with OAB.

PATIENT SUMMARY

Imidafenacin is as effective as tolterodine for the treatment of OAB.

Physiological based pharmacokinetic modeling to estimate in vivo Ki of ketoconazole on renal P-gp using human drug-drug interaction study result of fesoterodine and ketoconazole

This study was conducted to estimate in vivo inhibition constant (Ki) of ketoconazole on renal P-glycoprotein (P-gp) using human drug-drug interaction (DDI) study result of fesoterodine and ketoconazole. Fesoterodine is a prodrug which is extensively hydrolyzed by non-specific esterases to the active metabolite 5-hydroxymethyl tolterodine (5-HMT). 5-HMT is then further metabolized via Cytochrome P450 (CYP) 2D6 and CYP3A4. It is reported that 5-HMT is a substrate of P-gp whereas fesoterodine is not. Renal clearance of 5-HMT is approximately two-times greater than renal glomerular filtration rate. This suggests the possibility that renal clearance of 5-HMT involves secretion by P-gp. Utilizing the available pharmacokinetic characteristics of fesoterodine and 5-HMT, we estimated in vivo Ki of ketoconazole on P-gp at kidney based on DDI study data using physiologically-based pharmacokinetic approach. The estimated in vivo Ki of ketoconazole for hepatic CYP3A4 (6.64 ng/mL) was consistent with the reported values. The in vivo Ki of ketoconazole for renal P-gp was successfully estimated as 2.27 ng/mL, which was notably lower than reported in vitro 50% inhibitory concentration (IC₅₀) values ranged 223-2440 ng/mL due to different condition between in vitro and in vivo.

Simultaneous usage of dementia medications and anticholinergics among Asians and Pacific Islanders

BACKGROUND

The simultaneous use of dementia medications and anticholinergic medications occurs frequently. Cholinesterase inhibitors and anticholinergic medications likely counteract one another, potentially exposing patients to medications with decreased benefit, more adverse effects, and higher cost of care. We identified the rate of concurrent prescriptions of cholinesterase inhibitors/memantine with anticholinergics in an urban hospital setting with a large Asian and Pacific Islander population.

METHODS

This study is a retrospective review of patients hospitalized from 1 January 2006 to 31 December 2010 at a general hospital who simultaneously received US Food and Drug Administration-approved dementia medications (galantamine, rivastigmine, donepezil, and/or memantine) and anticholinergics.

RESULTS

Overall, 304 patients receiving cholinesterase inhibitors/memantine also received anticholinergics. Of these patients, 64.1% were given high-potency anticholinergic medications, and 35.9% received medium-potency medications. Indications for the use of anticholinergic medication were urological (17.8%), gastrointestinal excluding nausea (32.6%), nausea (10.2%), psychiatric (7.9%), and other (31.6%). Asian patients received the combination of cholinesterase inhibitors/memantine and anticholinergics less frequently than Native Hawaiian or Caucasian patients (8.4% vs 12.2% and 13.3%, respectively; χ²  = 16.04, degrees of freedom = 2, P < 0.0003).

CONCLUSIONS

Simultaneous prescribing of cholinesterase inhibitors, memantine, and anticholinergic medications was significantly less common than in previous studies, with some ethnic variability. The less frequent occurrence of concurrent medications in the Asian population may be because of variations in the rate of indications or in tolerability for anticholinergic medications among the population.

Fesoterodine clinical efficacy and safety for the treatment of overactive bladder in relation to patient profiles: a systematic review

OBJECTIVE

To summarize published evidence on the pharmacology, efficacy, and safety of fesoterodine for the treatment of overactive bladder (OAB) symptoms in relation to patient clinical and demographic profiles.

METHODS

A systematic review of published articles on fesoterodine was conducted via a PubMed search. Articles were identified using the search term fesoterodine, with limits of human species and abstract available. Review and meta-analysis articles, validation studies, articles focused on treatment compliance/adherence, meeting abstracts, and articles not focused on oral fesoterodine administration in human subjects were excluded. Data from retained articles were summarized descriptively.

RESULTS

Of 137 articles identified, 61 (15 articles on the pharmacology and 46 articles on the efficacy and/or safety of fesoterodine) met inclusion criteria. Superiority trials demonstrated the additional efficacy of fesoterodine 8 mg versus fesoterodine 4 mg and tolterodine extended release 4 mg in treating OAB. Prospective trials in specific patient populations indicated beneficial effects of fesoterodine in elderly patients, vulnerable elderly patients, patients dissatisfied with or with a suboptimal response to previous antimuscarinic therapy, patients with urge urinary incontinence (UUI) or nocturnal urgency, and men with persistent LUTS during alpha-blocker treatment. With two effective doses, the fesoterodine dose can be adjusted to achieve optimal efficacy and tolerability in individual patients. The most common adverse events during fesoterodine treatment are dry mouth and constipation.

CONCLUSIONS

Extensive evidence demonstrates the efficacy and safety of fesoterodine in relieving OAB symptoms, including urgency, urinary frequency, UUI, and nocturnal urgency, in patients with various clinical and demographic profiles. Trial results provide valuable information on fesoterodine treatment in specific patient populations, including both elderly and vulnerable elderly patients. Potential limitations of this review are that only English language articles in PubMed were searched and included.