a is:
The tablet also contains the following inactive ingredients: colloidal silicon dioxide (NF), ethylcellulose (NF), hydrogenated castor oil (NF), hydroxypropyl methylcellulose (USP), magnesium stearate (NF), mannitol (USP), microcrystalline cellulose (NF), povidone (USP), and yellow ferric oxide (NF).
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12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
Alfuzosin is a selective antagonist of post-synaptic alpha1-adrenoreceptors, which are located in the prostate, bladder base, bladder neck, prostatic capsule, and prostatic urethra.
12.2 Pharmacodynamics
Alfuzosin exhibits selectivity for alpha adrenergic receptors in the lower urinary tract. Blockade of these adrenoreceptors can cause smooth muscle in the bladder neck and prostate to relax, resulting in an improvement in urine flow and a reduction in symptoms of BPH.
Cardiac Electrophysiology
The effect of 10 mg and 40 mg alfuzosin on QT interval was eva luated in a double-blind, randomized, placebo and active-controlled (moxifloxacin 400 mg), 4-way crossover single dose study in 45 healthy white male subjects aged 19 to 45 years. The QT interval was measured at the time of peak alfuzosin plasma concentrations. The 40 mg dose of alfuzosin was chosen because this dose achieves higher blood levels than those achieved with the co-administration of UROXATRAL and ketoconazole 400 mg. Table 3 summarizes the effect on uncorrected QT and mean corrected QT interval (QTc) with different methods of correction (Fridericia, population-specific and subject-specific correction methods) at the time of peak alfuzosin plasma concentrations. No single one of these correction methodologies is known to be more valid. The mean change of heart rate associated with a 10 mg dose of alfuzosin in this study was 5.2 beats/minute and 5.8 beats/minute with 40 mg alfuzosin. The change in heart rate with moxifloxacin was 2.8 beats/minute.
Table 3. Mean QT and QTc changes in msec (95% CI) from baseline at Tmax (relative to placebo) with different methodologies to correct for effect of heart rate. Drug/Dose QT Fridericia method Population-specific method Subject-specific method
*
Active control
Alfuzosin
10 mg -5.8
(-10.2, -1.4) 4.9
(0.9, 8.8) 1.8
(-1.4, 5.0) 1.8
(-1.3, 5.0)
Alfuzosin
40 mg -4.2
(-8.5, 0.2) 7.7
(1.9, 13.5) 4.2
(-0.6, 9.0) 4.3
(-0.5, 9.2)
Moxifloxacin
* 400 mg 6.9
(2.3, 11.5) 12.7
(8.6, 16.8) 11.0
(7.0, 15.0) 11.1
(7.2, 15.0)
The QT effect appeared greater for 40 mg compared to 10 mg alfuzosin. The effect of the highest alfuzosin dose (four times the therapeutic dose) studied did not appear as large as that of the active control moxifloxacin at its therapeutic dose. This study, however, was not designed to make direct statistical comparisons between the drugs or the dose levels. There has been no signal of Torsade de Pointes in the extensive post-marketing experience with alfuzosin outside the United States.
A separate post-marketing QT study eva luated the effect of the co-administration of 10 mg alfuzosin with a drug of similar QT effect size. In this study, the mean placebo-subtracted QTcF increase of alfuzosin 10 mg alone was 1.9 msec (upperbound 95% CI, 5.5 msec). The concomitant administration of the two drugs showed an increased QT effect when compared with either drug alone. This QTcF increase [5.9 msec (UB 95% CI, 9.4 msec)] was not more than additive. Although this study was not designed to make direct statistical compar |
