12.3 Pharmacokinetics
The pharmacokinetics of tamsulosin hydrochloride have been evaluated in adult 
healthy volunteers and patients with BPH after single and/or multiple 
administration with doses ranging from 0.1 mg to 1 mg. 
Absorption 
Absorption of tamsulosin hydrochloride from 
tamsulosin hydrochloride capsules 0.4 mg is essentially complete (>90%) 
following oral administration under fasting conditions. Tamsulosin hydrochloride 
exhibits linear kinetics following single and multiple dosing, with achievement 
of steady-state concentrations by the fifth day of once-a-day dosing. 
Effect of Food 
The time to maximum 
concentration (T
max) is reached by four to five hours 
under fasting conditions and by six to seven hours when tamsulosin hydrochloride 
capsules are administered with food. Taking tamsulosin hydrochloride under 
fasted conditions results in a 30% increase in bioavailability (AUC) and 40% to 
70% increase in peak concentrations (C
max) compared to 
fed conditions (Figure 1). 
Figure 1 Mean Plasma 
Tamsulosin Hydrochloride Concentrations Following Single-Dose Administration of 
Tamsulosin Hydrochloride Capsules 0.4 mg Under Fasted and Fed Conditions (n=8) 
The effects of food on the pharmacokinetics of tamsulosin hydrochloride are 
consistent regardless of whether a tamsulosin hydrochloride capsule is taken 
with a light breakfast or a high-fat breakfast (Table 2). 
Table 2 Mean (± S.D.) Pharmacokinetic Parameters Following Tamsulosin 
Hydrochloride Capsules 0.4 mg Once Daily or 0.8 mg Once Daily with a Light 
Breakfast, High-Fat Breakfast or Fasted
C
min = observed minimum concentration 
C
max = observed maximum tamsulosin hydrochloride plasma 
concentration 
T
max = median time-to-maximum 
concentration 
T
1/2 = observed half-life 
AUC
τ = area under the tamsulosin hydrochloride plasma time curve 
over the dosing interval 
Distribution 
The mean steady-state apparent volume of 
distribution of tamsulosin hydrochloride after intravenous administration to ten 
healthy male adults was 16 L, which is suggestive of distribution into 
extracellular fluids in the body.
Tamsulosin hydrochloride is extensively 
bound to human plasma proteins (94% to 99%), primarily alpha
1 acid glycoprotein 
(AAG), with linear binding over a wide concentration range (20 to 600 ng/mL). 
The results of two-way 
in vitro studies indicate that 
the binding of tamsulosin hydrochloride to human plasma proteins is not affected 
by amitriptyline, diclofenac, glyburide, simvastatin plus simvastatin-hydroxy 
acid metabolite, warfarin, diazepam, propranolol, trichlormethiazide, or 
chlormadinone. Likewise, tamsulosin hydrochloride had no effect on the extent of 
binding of these drugs. 
Metabolism 
There 
is no enantiomeric bioconversion from tamsulosin hydrochloride [R(-) isomer] to 
the S(+) isomer in humans. Tamsulosin hydrochloride is extensively metabolized 
by cytochrome P450 enzymes in the liver and less than 10% of the dose is 
excreted in urine unchanged. However, the pharmacokinetic profile of the 
metabolites in humans has not been established. Tamsulosin is extensively 
metabolized, mainly by CYP3A4 and CYP2D6, as well as via some minor 
participation of other CYP isoenzymes. Inhibition of hepatic drug-metabolizing 
enzymes may lead to increased exposure to tamsulosin [ 
see Warnings and Precautions (5.2) and Drug Interactions 
(7.1)]. The metabolites of tamsulosin hydrochloride undergo extensive 
conjugation to glucuronide or sulfate prior to renal excretion. 
Incubations with human liver microsomes showed no evidence of clinically 
significant metabolic interactions between tamsulosin hydrochloride and 
amitriptyline, albuterol (beta agonist), glyburide (glibenclamide) and 
finasteride (5alpha-reductase inhibitor for treatment of BPH). However, results 
of the in vitro testing of the tamsulosin hydrochloride interaction with 
diclofenac and warfarin were equivocal. 
Excretion 
On administration of the radiolabeled dose of tamsulosin 
hydrochloride to four healthy volunteers, 97% of the administered radioactivity 
was recovered, with urine (76%) representing the primary route of excretion 
compared to feces (21%) over 168 hours. 
Following intravenous or oral 
administration of an immediate-release formulation, the elimination half-life of 
tamsulosin hydrochloride in plasma ranged from five to seven hours. Because of 
absorption rate-controlled pharmacokinetics with tamsulosin hydrochloride 
capsules, the apparent half-life of tamsulosin hydrochloride is approximately 9 
to 13 hours in healthy volunteers and 14 to 15 hours in the target population. 
Tamsulosin hydrochloride undergoes restrictive clearance in humans, with 
a relatively low systemic clearance (2.88 L/h).
Special Populations
Pediatric Use 
Tamsulosin hydrochloride capsules are not indicated for use in 
pediatric populations [ 
see Use in Specific Populations 
(8.4)]. 
Geriatric (Age) Use 
Cross-study comparison of tamsulosin hydrochloride capsules overall 
exposure (AUC) and half-life indicates that the pharmacokinetic disposition of 
tamsulosin hydrochloride may be slightly prolonged in geriatric males compared 
to young, healthy male volunteers. Intrinsic clearance is independent of 
tamsulosin hydrochloride binding to AAG, but diminishes with age, resulting in a 
40% overall higher exposure (AUC) in subjects of age 55 to 75 years compared to 
subjects of age 20 to 32 years [ 
see Use in Specific Populations (8.5)]. 
Renal Impairment 
The pharmacokinetics 
of tamsulosin hydrochloride have been compared in 6 subjects with mild-moderate 
(30 ≤CL
cr <70 mL/min/1.73 m
2) 
or moderate-severe (10 ≤CL
cr <30 mL/min/1.73 m
2) renal impairment and 6 normal subjects (CL
cr >90 mL/min/1.73 m
2). While a change in the overall plasma concentration of 
tamsulosin hydrochloride was observed as the result of altered binding to AAG, 
the unbound (active) concentration of tamsulosin hydrochloride, as well as the 
intrinsic clearance, remained relatively constant. Therefore, patients with 
renal impairment do not require an adjustment in tamsulosin hydrochloride 
capsules dosing. However, patients with endstage renal disease (CL
cr <10 mL/min/1.73 m
2) have not been 
studied [
see Use in Specific Populations (8.6)]. 
Hepatic Impairment 
The pharmacokinetics 
of tamsulosin hydrochloride have been compared in 8 subjects with moderate 
hepatic impairment (Child-Pugh's classification: Grades A and B) and 8 normal 
subjects. While a change in the overall plasma concentration of tamsulosin 
hydrochloride was observed as the result of altered binding to AAG, the unbound 
(active) concentration of tamsulosin hydrochloride does not change 
significantly, with only a modest (32%) change in intrinsic clearance of unbound 
tamsulosin hydrochloride. Therefore, patients with moderate hepatic impairment 
do not require an adjustment in tamsulosin hydrochloride capsules dosage. 
Tamsulosin hydrochloride have not been studied in patients with severe hepatic 
impairment [
see Use in Specific Populations (8.7)]. 
Drug Interactions 
Cytochrome P450 Inhibition 
Strong and Moderate Inhibitors of CYP3A4 or CYP2D6 
The 
effects of ketoconazole (a strong inhibitor of CYP3A4) at 400 mg once daily for 
5 days on the pharmacokinetics of a single tamsulosin hydrochloride capsule 0.4 
mg dose was investigated in 24 healthy volunteers (age range 23 to 47 years). 
Concomitant treatment with ketoconazole resulted in an increase in the C
max and AUC of tamsulosin by a factor of 2.2 and 2.8, 
respectively [
see Warnings and Precautions (5.2) and 
Clinical Pharmacology (12.3)]. The effects of concomitant administration 
of a moderate CYP3A4 inhibitor (e.g., erythromycin) on the pharmacokinetics of 
tamsulosin hydrochloride have not been evaluated [
see Warnings and Precautions (5.2) and Drug Interactions 
(7.1)]. 
The effects of paroxetine (a strong inhibitor of CYP2D6) 
at 20 mg once daily for 9 days on the pharmacokinetics of a single tamsulosin 
hydrochloride capsule 0.4 mg dose was investigated in 24 healthy volunteers (age 
range 23 to 47 years). Concomitant treatment with paroxetine resulted in an 
increase in the C
max and AUC of tamsulosin by a factor of 
1.3 and 1.6, respectively [
see Warnings and Precautions 
(5.2) and Drug Interactions (7.1)]. A similar increase in exposure is 
expected in CYP2D6 poor metabolizers (PM) as compared to extensive metabolizers 
(EM). A fraction of the population (about 7% of Caucasians and 2% of African 
Americans) are CYP2D6 PMs. Since CYP2D6 PMs cannot be readily identified and the 
potential for significant increase in tamsulosin exposure exists when tamsulosin 
hydrochloride 0.4 mg is coadministered with strong CYP3A4 inhibitors in CYP2D6 
PMs, tamsulosin hydrochloride 0.4 mg capsules should not be used in combination 
with strong inhibitors of CYP3A4 (e.g., ketoconazole) [
see Warnings and Precautions (5.2) and Drug Interactions 
(7.1)]. 
The effects of concomitant administration of a moderate 
CYP2D6 inhibitor (e.g., terbinafine) on the pharmacokinetics of tamsulosin 
hydrochloride have not been evaluated [
see Warnings and 
Precautions (5.2) and Drug Interactions (7.1)]. 
The effects of 
coadministration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin 
hydrochloride capsules have not been evaluated. However, there is a potential 
for significant increase in tamsulosin exposure when tamsulosin hydrochloride 
0.4 mg is coadministered with a combination of both CYP3A4 and CYP2D6 
inhibitors [
see Warnings and Precautions (5.2) and Drug 
Interactions (7.1)]. 
Cimetidine 
The effects of cimetidine at the highest recommended dose (400 mg 
every 6 hours for 6 days) on the pharmacokinetics of a single tamsulosin 
hydrochloride capsule 0.4 mg dose was investigated in 10 healthy volunteers (age 
range 21 to 38 years). Treatment with cimetidine resulted in a significant 
decrease (26%) in the clearance of tamsulosin hydrochloride, which resulted in a 
moderate increase in tamsulosin hydrochloride AUC (44%) [
see Warnings and Precautions (5.2) and Drug Interactions 
(7.1)]. 
Other Alpha Adrenergic Blocking 
Agents 
The pharmacokinetic and pharmacodynamic interactions between 
tamsulosin hydrochloride capsules and other alpha adrenergic blocking agents 
have not been determined; however, interactions between tamsulosin hydrochloride 
capsules and other alpha adrenergic blocking agents may be expected [
see Warnings and Precautions (5.2) and Drug Interactions 
(7.2)]. 
PDE5 Inhibitors 
Caution 
is advised when alpha adrenergic blocking agents including tamsulosin 
hydrochloride are coadministered with PDE5 inhibitors Alpha-adrenergic blockers 
and PDE5 inhibitors are both vasodilators that can lower blood pressure. 
Concomitant use of these two drug classes can potentially cause symptomatic 
hypotension [
see Warnings and Precautions (5.2) and Drug 
Interactions (7.3)] 
Warfarin 
A 
definitive drug-drug interaction study between tamsulosin hydrochloride and 
warfarin was not conducted. Results from limited 
in vitro and 
in vivo studies 
are inconclusive. Therefore, caution should be exercised with concomitant 
administration of warfarin and tamsulosin hydrochloride capsules [
see Warnings and Precautions (5.2) and Drug Interactions 
(7.4)]. 
Nifedipine, Atenolol, Enalapril 
In three studies in hypertensive subjects (age range 47 to 79 years) 
whose blood pressure was controlled with stable doses of nifedipine, atenolol, 
or enalapril for at least 3 months, tamsulosin hydrochloride capsules 0.4 mg for 
7 days followed by tamsulosin hydrochloride capsules 0.8 mg for another 7 days 
(n=8 per study) resulted in no clinically significant effects on blood pressure 
and pulse rate compared to placebo (n=4 per study). Therefore, dosage 
adjustments are not necessary when tamsulosin hydrochloride capsules are 
administered concomitantly with nifedipine, atenolol, or enalapril [
see Drug Interactions (7.5)]. 
Digoxin and Theophylline 
In two studies in healthy 
volunteers (n=10 per study; age range 19 to 39 years) receiving tamsulosin 
hydrochloride capsules 0.4 mg/day for 2 days, followed by tamsulosin 
hydrochloride capsules 0.8 mg/day for 5 to 8 days, single intravenous doses of 
digoxin 0.5 mg or theophylline 5 mg/kg resulted in no change in the 
pharmacokinetics of digoxin or theophylline. Therefore, dosage adjustments are 
not necessary when a tamsulosin hydrochloride capsule is administered 
concomitantly with digoxin or theophylline [
see Drug 
Interactions (7.6)]. 
Furosemide 
The pharmacokinetic and pharmacodynamic interaction between 
tamsulosin hydrochloride capsules 0.8 mg/day (steady-state) and furosemide 20 mg 
intravenously (single dose) was evaluated in ten healthy volunteers (age range 
21 to 40 years). Tamsulosin hydrochloride capsules had no effect on the 
pharmacodynamics (excretion of electrolytes) of furosemide. While furosemide 
produced an 11% to 12% reduction in tamsulosin hydrochloride C
max and AUC, these changes are expected to be clinically 
insignificant and do not require adjustment of the tamsulosin hydrochloride 
capsules dosage [
see Drug Interactions (7.7)].