Torrent

TOLTERODINE TARTRATE

tolterodine

Post-LOE

ORAL · CAPSULE, EXTENDED RELEASE

12.1 Mechanism of Action Tolterodine acts as a competitive antagonist of acetylcholine at postganglionic muscarinic receptors. Both urinary bladder contraction and salivation are mediated via cholinergic muscarinic receptors. After oral administration, tolterodine is metabolized in the liver, resulting in the formation of 5-hydroxymethyl tolterodine (5-HMT), the major pharmacologically active metabolite. 5-HMT, which exhibits an antimuscarinic activity similar to that of tolterodine, contributes significantly to the therapeutic effect. Both tolterodine and 5-HMT exhibit a high specificity for muscarinic receptors, since both show negligible activity or affinity for other neurotransmitter receptors and other potential cellular targets, such as calcium channels. 12.2 Pharmacodynamics Tolterodine has a pronounced effect on bladder function. Effects on urodynamic parameters before and 1 and 5 hours after a single 6.4 mg dose of tolterodine immediate release were determined in healthy volunteers. The main effects of tolterodine at 1 and 5 hours were an increase in residual urine, reflecting an incomplete emptying of the bladder, and a decrease in detrusor pressure. These findings are consistent with an antimuscarinic action on the lower urinary tract. Cardiac Electrophysiology The effect of 2 mg BID and 4 mg BID of tolterodine tartrate immediate release (tolterodine IR) tablets on the QT interval was evaluated in a 4-way crossover, double-blind, placebo- and active-controlled (moxifloxacin 400 mg QD) study in healthy male (N=25) and female (N=23) volunteers aged 18 to 55 years. Study subjects [approximately equal representation of CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs)] completed sequential 4-day periods of dosing with moxifloxacin 400 mg QD, tolterodine 2 mg BID, tolterodine 4 mg BID, and placebo. The 4 mg BID dose of tolterodine IR (two times the highest recommended dose) was chosen because this dose results in tolterodine exposure similar to that observed upon coadministration of tolterodine 2 mg BID with potent CYP3A4 inhibitors in patients who are CYP2D6 poor metabolizers [see DRUG INTERACTIONS ( )]. QT interval was measured over a 12-hour period following dosing, including the time of peak plasma concentration (T max ) of tolterodine and at steady state (Day 4 of dosing). Table 2 summarizes the mean change from baseline to steady state in corrected QT interval (QTc) relative to placebo at the time of peak tolterodine (1 hour) and moxifloxacin (2 hour) concentrations. Both Fridericia's (QTcF) and a population-specific (QTcP) method were used to correct QT interval for heart rate. No single QT correction method is known to be more valid than others. QT interval was measured manually and by machine, and data from both are presented. The mean increase of heart rate associated with a 4 mg/day dose of tolterodine in this study was 2.0 beats/minute and 6.3 beats/minute with 8 mg/day tolterodine. The change in heart rate with moxifloxacin was 0.5 beats/minute. Table 2. Mean (Cl) change in QTc from baseline to steady state (Day 4 of dosing) at T max (relative to placebo) Drug/Dose N QT c F QT c F QT c P QT c P Tolterodine 2 mg BID* 48 5.01 (0.28, 9.74) 1.16 (-2.99, 5.30) 4.45 (-0.37, 9.26) 2.00 (-1.81, 5.81) Tolterodine 4 mg BID* 48 11.84 (7.11, 16.58) 5.63 (1.48, 9.77) 10.31 (5.49, 15.12) 8.34 (4.53, 12.15) Moxifloxacin 400 mg QD† 45 19.26‡ (15.49, 23.03) 8.90 (4.77, 13.03) 19.10‡ (15.32, 22.89) 9.29 (5.34, 13.24) *At T max of 1 hr; 95% Confidence Interval. †At T max of 2 hr; 90% Confidence Interval. ‡The effect on QT interval with 4 days of moxifloxacin dosing inthis QT trial may be greater than typically observed in QT trials of other drugs. The reason for the difference between machine and manual read of QT interval is unclear. The QT effect of tolterodine immediate release tablets appeared greater for 8 mg/day (two times the therapeutic dose) compared to 4 mg/day. The effect of tolterodine 8 mg/day was not as large as that observed after four days of therapeutic dosing with the active control moxifloxacin. However, the confidence intervals overlapped. Tolterodine's effect on QT interval was found to correlate with plasma concentration of tolterodine. There appeared to be a greater QTc interval increase in CYP2D6 poor metabolizers than in CYP2D6 extensive metabolizers after tolterodine treatment in this study. This study was not designed to make direct statistical comparisons between drugs or dose levels. There has been no association of Torsade de Pointes in the international post-marketing experience with tolterodine tartrate immediate-release tablets or tolterodine tartrate extended-release capsules [see WARNINGS AND PRECAUTIONS ( )]. 12.3 Pharmacokinetics Absorption: In a study with C-tolterodine solution in healthy volunteers who received a 5 mg oral dose, at least 77% of the radiolabeled dose was absorbed. C max and area under the concentration-time curve (AUC) determined after do

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