CLINICAL PHARMACOLOGY
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.
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 evaluated 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 |
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 (S. 6. 16.3) |
11.0 (7.0. 15.0) |
11.1 (7.2. 15.0) |
*Active control |
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 evaluated 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 comparisons between drugs, the QT increase
with both drugs given together appeared to be lower than the QTcF increase seen
with the positive control moxifloxacin 400 mg [10.2 msec (UB 95% CI, 13.8
msec)]. The clinical impact of these QTc changes is unknown.
Pharmacokinetics
The pharmacokinetics of UROXATRAL have been evaluated in
adult healthy male volunteers after single and/or multiple administration with
daily doses ranging from 7.5 mg to 30 mg, and in patients with BPH at doses
from 7.5 mg to 15 mg.
Absorption
The absolute bioavailability of UROXATRAL 10 mg tablets
under fed conditions is 49%. Following multiple dosing of 10 mg UROXATRAL under
fed conditions, the time to maximum concentration is 8 hours. Cmax and AUC0-24 are
13.6 (SD = 5.6) ng/mL and 194 (SD = 75) ng·h/mL, respectively. UROXATRAL
exhibits linear kinetics following single and multiple dosing up to 30 mg.
Steady-state plasma levels are reached with the second dose of UROXATRAL
administration. Steady-state alfuzosin plasma concentrations are 1.2-to
1.6-fold higher than those observed after a single administration.
Effect of Food
As illustrated in Figure 1, the extent of absorption is 50%
lower under fasting conditions. Therefore, UROXATRAL should be taken with food
and with the same meal each day [see DOSAGE AND ADMINISTRATION].
Figure 1 :Mean (SEM) Alfuzosin Plasma Concentration-Time
Profiles after a Single Administration of UROXATRAL 10 mg tablets to 8 Healthy
Middle-Aged Male Volunteers in Fed and Fasted States
Distribution
The volume of distribution following intravenous
administration in healthy male middle-aged volunteers was 3.2 L/kg. Results of in
vitro studies indicate that alfuzosin is moderately bound to human plasma
proteins (82% to 90%), with linear binding over a wide concentration range (5
to 5,000 ng/mL).
Metabolism
Alfuzosin undergoes extensive metabolism by the liver,
with only 11% of the administered dose excreted unchanged in the urine.
Alfuzosin is metabolized by three metabolic pathways: oxidation,
O-demethylation, and N-dealkylation. The metabolites are not pharmacologically
active. CYP3A4 is the principal hepatic enzyme isoform involved in its
metabolism.
Excretion
Following oral administration of 14C-labeled
alfuzosin solution, the recovery of radioactivity after 7 days (expressed as a
percentage of the administered dose) was 69% in feces and 24% in urine.
Following oral administration of UROXATRAL 10 mg tablets, the apparent elimination
half-life is 10 hours.
Specific Populations
Geriatric Use: In a pharmacokinetic assessment
during phase 3 clinical studies in patients with BPH, there was no relationship
between peak plasma concentrations of alfuzosin and age. However, trough levels
were positively correlated with age. The concentrations in subjects ≥75 Â years
of age were approximately 35% greater than in those below 65 years of age.
Renal Impairment: The Pharmacokinetic profiles of
UROXATRAL 10 mg tablets in subjects with normal renal function (CLCR > 80
mL/min), mild impairment (CLCR 60 to 80 mL/min), moderate impairment (CLCR 30
to 59 mL/min), and severe impairment (CLCR <30 mL/min) were compared. These
clearances were calculated by the Cockcroft-Gault formula. Relative to subjects
with normal renal function, the mean Cmax and AUC values were increased by
approximately 50% in patients with mild, moderate, or severe renal impairment [see
WARNINGS AND PRECAUTIONS and Use In Specific Populations].
Hepatic Impairment: The pharmacokinetics of
UROXATRAL have not been studied in patients with mild hepatic impairment. In
patients with moderate or severe hepatic insufficiency (Child-Pugh categories B
and C), the plasma apparent clearance (CL/F) was reduced to approximately
one-third to one-fourth that observed in healthy subjects. This reduction in
clearance results in three to four-fold higher plasma concentrations of
alfuzosin in these patients compared to healthy subjects. Therefore, UROXATRAL
is contraindicated in patients with moderate to severe hepatic impairment [see CONTRAINDICATIONS,
WARNINGS AND PRECAUTIONS and Use In Specific Populations].
Pediatric Use: UROXATRAL tablets are not indicated
for use in the pediatric population [see INDICATIONS AND USAGE and Use
in Specific Populations].
Drug-Drug Interactions
Metabolic Interactions
CYP3A4 is the principal hepatic enzyme isoform involved
in the metabolism of alfuzosin.
Potent CYP3A4 Inhibitors
Repeated oral administration of 400 mg/day of
ketoconazole, a potent inhibitor of CYP3A4, increased alfuzosin Cmax by
2.3-fold and AUClast by 3.2-fold, following a single 10 mg dose of alfuzosin.
In another study, repeated oral administration of a lower
(200 mg/day) dose of ketoconazole increased alfuzosin Cmax by 2.1-fold and AUClast
by 2.5-fold, following a single 10 mg dose of alfuzosin.
Therefore, UROXATRAL is contraindicated for
co-administration with potent inhibitors of CYP3A4 (e.g., ketoconazole, itraconazole,
or ritonavir) because of increased alfuzosin exposure[see CONTRAINDICATIONS,
WARNINGS AND PRECAUTIONS and DRUG INTERACTIONS].
Moderate CYP3A4 Inhibitors
Diltiazem: Repeated co-administration of 240
mg/day of diltiazem, a moderately-potent inhibitor of CYP3A4, with 7.5 mg/day
(2.5 mg three times daily) alfuzosin (equivalent to the exposure with
UROXATRAL) increased the Cmax and AUC0-24 of alfuzosin 1.5-and 1.3-fold,
respectively. Alfuzosin increased the Cmax and AUC0-12 of diltiazem 1.4-fold.
Although no changes in blood pressure were observed in this study, diltiazem is
an antihypertensive medication and the combination of UROXATRAL and
antihypertensive medications has the potential to cause hypotension in some
patients [see WARNINGS AND PRECAUTIONS].
In human liver microsomes, at concentrations that are
achieved at the therapeutic dose, alfuzosin did not inhibit CYP1A2, 2A6, 2C9,
2C19, 2D6 or 3A4 isoenzymes. In primary culture of human hepatocytes, alfuzosin
did not induce CYP1A, 2A6 or 3A4 isoenzymes.
Other Interactions
Warfarin: Multiple dose administration of an
immediate release tablet formulation of alfuzosin 5 mg twice daily for six days
to six healthy male volunteers did not affect the pharmacological response to a
single 25 mg oral dose of warfarin.
Digoxin: Repeated co-administration of UROXATRAL
10 mg tablets and digoxin 0.25 mg/day for 7 days did not influence the
steady-state pharmacokinetics of either drug.
Cimetidine: Repeated administration of 1 g/day
cimetidine increased both alfuzosin Cmax and AUC values by 20%.
Atenolol: Single administration of 100 mg atenolol
with a single dose of 2.5 mg of an immediate release alfuzosin tablet in eight
healthy young male volunteers increased alfuzosin Cmax and AUC values by 28%
and 21%, respectively. Alfuzosin increased atenolol Cmax and AUC values by 26%
and 14%, respectively. In this study, the combination of alfuzosin with
atenolol caused significant reductions in mean blood pressure and in mean heart
rate. [see WARNINGS AND PRECAUTIONS].
Hydrochlorothiazide: Single administration of 25
mg hydrochlorothiazide did not modify the pharmacokinetic parameters of
alfuzosin. There was no evidence of pharmacodynamic interaction between
alfuzosin and hydrochlorothiazide in the 8 patients in this study.
Clinical Studies
Three randomized placebo-controlled, double-blind,
parallel-arm, 12-week trials were conducted with the 10 mg daily dose of
alfuzosin. In these three trials, 1,608 patients [mean age 64.2 years, range
49-92 years; Caucasian (96.1%), Black (1.6%), Asian (1.1%), Other (1.2%)] were
randomized and 473 patients received UROXATRAL 10 mg daily. Table 4 provides
the results of the three trials that evaluated the 10 mg dose.
There were two primary efficacy variables in these three
studies. The International Prostate Symptom Score (IPSS, or AUA Symptom Score)
consists of seven questions that assess the severity of both irritative
(frequency, urgency, nocturia) and obstructive (incomplete emptying, stopping
and starting, weak stream, and pushing or straining) symptoms, with possible
scores ranging from 0 to 35 with higher numerical scores on the IPSS total
symptom score representing greater severity of symptoms. The second efficacy
variable was peak urinary flow rate. The peak flow rate was measured just prior
to the next dose in study 2 and on average at 16 hours post-dosing in trials 1
and 3.
There was a statistically significant reduction from
baseline to last assessment (Week 12) in the IPSS total symptom score versus
placebo in all three studies, indicating a reduction in symptom severity (Table
5 and Figures 2, 3, and 4).
Table 4 :Mean Change (SD) from Baseline to week 12 in
International Prostate Symptom Score in Three Randomized, Controlled, Double
Blind Trials
Symptom Score |
Trial 1 |
Trial 2 |
Trial 3 |
Placebo
(n=167) |
UROXATRAL 10 mg
(n=170) |
Placebo
(n=152) |
UROXATRAL 10 mg
(n=137) |
Placebo
(n=150) |
UROXATRAL 10 mg
(n=151) |
Total symptom score |
Baseline |
18.2 (6.4) |
18.2 (6.3) |
17.7 (4.1) |
17.3 (3.5) |
17.7 (5.0) |
18.0 (5.4) |
Changea |
-1.6 (5.8) |
-3.6 (4.8) |
-4.9 (5.9) |
-6.9 (4.9) |
-4.6 (5.8) |
-6.5 (5.2) |
p-value |
0.001 |
0.002 |
0.007 |
aDifference between baseline and week 12. |
Figure 2 :Mean Change from Baseline in IPSS Total
Symptom Score: Trial 1
Figure 3 :Mean Change from Baseline in IPSS Total
Symptom Score: Trial 2
Figure 4 : Mean Change from Baseline in IPSS Total
Symptom Score: Trial 3
Peak urinary flow rate was increased statistically
significantly from baseline to last assessment (Week 12) versus placebo in
trials 1 and 2 (Table 5 and Figures 5, 6, and 7).
Table 5 :Mean (SD) Change from Baseline to Week 12 in
Peak Urine Flow Rate (mL/sec) in Three Randomized, Controlled, Double-Blind
Trials
|
Trial 1 |
Trial 2 |
Trial 3 |
Placebo
(n=167) |
UROXATRAL 10 mg
(n=170) |
Placebo
(n=147) |
UROXATRAL 10 mg
(n=136) |
Placebo
(n=150) |
UROXATRAL 10 mg
(n=151) |
Mean Peak flow rate |
Baseline |
10.2 (4.0) |
9.9 (3.9) |
9.2 (2.0) |
9.4 (1.9) |
9.3 (2.6) |
9.5 (3.0) |
Changea |
0.2 (3.5) |
1.7 (4.2) |
1.4 (3.2) |
2.3 (3.6) |
0.9 (3.0) |
1.5 (3.3) |
p-value |
0.0004 |
0.03 |
0.22 |
aDifference between baseline and week 12. |
Figure 5 : Mean Change from Baseline in Peak Urine
Flow Rate (mL/s): Trial 1
Figure 6 : Mean Change from Baseline in Peak Urine Flow
Rate (mL/s): Trial 2
Figure 7 :Mean Change from Baseline in Peak Urine Flow
Rate (mL/s): Trial 3
Mean total IPSS decreased at the first scheduled
observation at Day 28 and mean peak flow rate increased starting at the first
scheduled observation at Day 14 in trials 2 and 3 and Day 28 in trial 1.