Bioequivalence Studies of a Reformulated Dutasteride and Tamsulosin Hydrochloride Combination Capsule and a Commercially Available Formulation

Effects of Cytochrome P450 and Transporter Polymorphisms on the Bioavailability and Safety of Dutasteride and Tamsulosin

Dutasteride and tamsulosin are one of the first-line combination therapies for the management of benign prostatic hyperplasia (BPH). Despite being more effective than monotherapies, they produce frequent adverse drug reactions (ADRs). Institutions such as Food and Drug Administration and European Medicines Agency recommend precaution with CYP2D6 poor metabolizers (PMs) that receive CYP3A4 inhibitors and tamsulosin. However, no specific pharmacogenetic guideline exists for tamsulosin. Furthermore, to date, no pharmacogenetic information is available for dutasteride. Henceforth, we studied the pharmacokinetics and safety of dutasteride/tamsulosin 0.5 mg/0.4 mg capsules according to 76 polymorphisms in 17 candidate pharmacogenes. The study population comprised 79 healthy male volunteers enrolled in three bioequivalence, phase-I, crossover, open, randomized clinical trials with different study designs: the first was single dose in fed state, the second was a single dose in fasting state, and the third was a multiple dose. As key findings, CYP2D6 PMs (i.e., *4/*4 and *4/*5 subjects) and intermediate metabolizers (IMs) (i.e., *1/*4, *1/*5, *4/*15 individuals) presented higher AUC (p = 0.004), higher t_1/2 (p = 0.008), and lower Cl/F (p = 0.006) when compared with NMs (*1/*1 individuals) and UMs (1/*1 × 2 individuals) after multiple testing correction. Moreover, fed volunteers showed significantly higher t_max than fasting individuals. Nominally significant associations were observed between dutasteride exposure and CYP3A4 and CYP3A5 genotype and between tamsulosin and ABCG2, CYP3A5, and SLC22A1 genotypes. No association between the occurrence of adverse drug reactions and genotype was observed. Nonetheless, higher incidence of adverse events was found in a multiple-dose clinical trial. Based on our results, we suggest that dose adjustments for PMs and UMs could be considered to ensure drug safety and effectiveness, respectively. Further studies are warranted to confirm other pharmacogenetic associations.

Bioequivalence Assessment of an Oral Fixed-Dose Formulation of Dutasteride-Tamsulosin 0.5 mg/0.4 mg: A Randomized, Single-Blind, Single-Dose, 2-Period Crossover Study in Mexican Population Under Fasted Conditions

The aim of the present study was to compare the bioavailability and to demonstrate the bioequivalence between a dutasteride-tamsulosin 0.5 mg/0.4 mg capsule formulation and the regulatory reference drug (Combodart®, GlaxoSmithKline). A randomized, single-blind, single-dose, 2-way crossover study under fasting conditions, with at least a 28-day washout period was carried out in healthy volunteers. Plasma concentrations of drugs were determined by high-performance liquid chromatography-tandem mass spectrometry. The pharmacokinetic analysis included maximum plasma concentration (C_max ), area under the plasma concentration-time curve (AUC) from time 0 to 72 hours, and AUC from baseline to infinity. The test formulation was considered bioequivalent if the geometric mean ratios (test/reference) were within the predetermined range of 80% to 125%. Safety and tolerability were evaluated by clinical assessment. The confidence intervals for the log-transformed test/reference ratios for dutasteride, C_max (95.4-109.2) and AUC from baseline to 72 hours (93.2-109.1), and for tamsulosin, C_max (101.9-119.8), AUC from baseline to the last quantifiable concentration (91.4-106.3) and AUC from baseline to infinity (90.9-103.3), were within the allowed limit specified by the regulatory authorities (80%-125%). In addition, both test and reference drugs were safe and tolerated. These results demonstrated the bioequivalence of test product (Dakart®) compared with Combodart®.

Ameliorative effect of morin on dutasteride-tamsulosin-induced testicular oxidative stress in rat

OBJECTIVES

Dutasteride-Tamsulosin (DUT-TAM), a drug of choice for the treatment of prostate enlargement (Benign Prostatic Hyperplasia, BPH) has been implicated in testicular toxicity. This study investigated the protective effect of morin, a plant-derived flavonoid on DUT-TAM-induced testicular toxicity in Wistar rat.

METHODS

Twenty-four male Wistar rats (110-140 g) were randomly divided into four treatment groups (n=6). Group A animals served as the control and were administered olive oil, Group B animals were administered 5.4 mg/kg b.w. of dutasteride + 3.4 mg/kg b.w of tamsulosin., Group C animals were administered 100 mg/kg b.w. of morin, while Group D animals were administered DUT-TAM (5.4 mg/kg b.w. of dutasteride + 3.4 mg/kg b.w. of tamsulosin) and morin (100 mg/kg b.w.). The administration lasted for two weeks.

RESULTS

DUT-TAM-induced abnormal sperm morphology (31.8%), significantly reduced (p<0.05) sperm count, sperm motility, live-dead sperm ratio, testicular superoxide dismutase (SOD), catalase, glutathione-S-transferase (GST) and acid phosphatase (ACP) activities, as well as the levels of ascorbic acid and reduced glutathione (GSH) which were ameliorated by co-treatment with morin. Also, DUT-TAM-induced increase in testicular malondialdehyde level and the activities of alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT) and lactate dehydrogenase (LDH) were significantly reversed (p<0.05) by co-treatment with morin.

CONCLUSIONS

These results indicated the protective ability of morin against Dutasteride-Tamsulosin-induced testicular toxicity and oxidative stress.

Relative Bioavailability of Fixed-Dose Combinations of Tamsulosin and Dutasteride: Results From 2 Randomized Trials in Healthy Male Volunteers

The relative bioavailabilities of dutasteride/tamsulosin hydrochloride 0.5 mg/0.2 mg fixed-dose combination (FDC) capsules compared with coadministered reference products (1 dutasteride 0.5-mg capsule [Avodart^® ] + 1 tamsulosin hydrochloride 0.2-mg orally disintegrating tablet [Harnal D^® ]) were investigated in 2 clinical trials under fasted and fed conditions (ClinicalTrials.gov NCT02184585 and NCT02509104). Both trials were open-label, randomized, single-dose, crossover studies in healthy male adults aged 18-65 years. Trial 1 evaluated 2 formulations (FDC1 and FDC2), and trial 2 evaluated a third formulation (FDC3). The primary end points were dutasteride area under the concentration-time curve from time 0 to t (AUC_(0-t) ) and peak plasma concentration (C_max ) and tamsulosin AUC_(0-∞) , AUC_(0-t) , and C_max . The formulations were considered to be bioequivalent if the 90%CIs for the geometric mean ratios for each end point were within the range of 0.80-1.25. For FDC1 in trial 1, bioequivalence criteria were not met for dutasteride C_max or AUC in the fasted state or for tamsulosin C_max in the fasted or fed states. For FDC2 in trial 1, all bioequivalence criteria were met except for tamsulosin C_max in the fasted state. For FDC3 in trial 2, bioequivalence criteria were met for all dutasteride and tamsulosin end points in both the fed and fasted states. Safety profiles were similar for all FDC formulations and combination treatments.