Dosing and uses of Flomax (tamsulosin)
Adult dosage forms and strengths
capsule
- 0.4mg
Benign Prostatic Hypertrophy
0.4 mg PO once daily, 30 minutes after same meal each day; if response is inadequate after 2-4 weeks, may be increased to 0.8 mg once daily; if therapy is interrupted, should be resumed at 0.4 mg once daily
Bladder Outlet Obstruction
Relief of symptoms
0.4 mg PO once daily
Ureteral Stones
Facilitation of stone expulsion
0.4 mg PO once daily; discontinued after successful expulsion (average, 1-2 weeks)
Dosing Modifications
Renal impairment
- CrCl ≥10 mL/min: Dosage adjustment not necessary
- CrCl <10 mL/min: Not studied
Hepatic impairment
- Mild to moderate: Dosage adjustment not necessary
- Severe: Not studied
Pediatric dosage forms and strengths
Safety and efficacy not established
Flomax (tamsulosin) adverse (side) effects
>10%
Headache (19-21%)
Orthostatic hypotension (6-19%)
Rhinitis (13-18%)
Abnormal ejaculation (8-18%)
Dizziness (15-17%)
Arthralgia (11%)
Infection (9-11%)
1-10%
Asthenia (8%)
Back pain (7-8%)
Skin rash (7%)
Pharyngitis (5-6%)
Diarrhea (4-6%)
Myalgia (5%)
Chest pain (4%)
Cough (3-4%)
Somnolence (3-4%)
Nausea (2-4%)
Sinusitis (2-4%)
Abdominal discomfort (2-3%)
Bitter taste (2-3%)
Decreased libido (1-2%)
Insomnia (1-2%)
Postmarketing Reports
Priapism (rare)
Signs and symptoms of orthostasis, including syncope
Infrequent reports of dyspnea, palpitations, hypotension, atrial fibrillation, arrhythmia, and tachycardia
Visual impairment
During cataract and glaucoma surgery, a variant of small pupil syndrome known as Intraoperative Floppy Iris Syndrome (IFIS) has been reported in association with alpha1 blocker therapy
Skin desquamation including reports of Stevens-Johnson syndrome, erythema multiforme, and dermatitis exfoliative
Constipation, vomiting, and epistaxis
Allergic-type reactions (eg, skin rash, urticaria, pruritus, angioedema, respiratory symptoms) have been reported with positive rechallenge
Dry mouth
Warnings
Contraindications
Hypersensitivity
Cautions
Use with caution in coronary artery disease, liver disease, general anesthesia
Orthostatic hypotension may occur
Priapism rarely reported
Prostatic cancer should be ruled out before therapy is initiated
May cause syncope (first-dose effect)
Discontinue if angina symptoms occur or worsen
Intraoperative floppy iris syndrome has been reported in patients receiving alpha1 blockers at time of cataract surgery; association is unclear
Patients with sulfa allergy have rarely developed allergic reaction; avoid use if previous sulfa allergy reactions have been life-threatening
Not for use as antihypertensive drug
May exacerbate heart failure
Pregnancy and lactation
Pregnancy category: B
Lactation: Women are unlikely to use drug
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Flomax (tamsulosin)
Mechanism of action
Blocks alpha1a adrenergic receptor in smooth muscle of prostate, decreasing bladder neck and urethral resistance
Absorption
Bioavailability: Fasting, 30%
Onset: 4-8 hr
Peak plasma time: With food, 6-7 hr; fasting, 4-5 hr
Distribution
Protein bound: 90%
Vd: 0.2 L/kg or 16 L
Metabolism
Metabolized in liver
Metabolites: Glucuronide and sulfate conjugates (inactive)
Elimination
Half-life: 14-15 hr
Excretion: Urine (76%), feces (21%)
