Flomax
Flomax
Generic Name
Flomax
Mechanism
- Selective α₁A‑adrenergic blockade:
- Tamsulosin binds preferentially to α₁A receptors located in the prostate, bladder neck, and proximal urethra.
- This reduces smooth‑muscle tone, leading to relaxation of the prostate and bladder neck.
- Result: decreased urethral resistance → improved urinary flow and reduced post‑void residual volume.
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Pharmacokinetics
| Parameter | Typical Value | Notes |
| Bioavailability | ~44% (after oral dosing) | Food may modestly increase absorption. |
| Elimination half‑life | 8–10 h | Steady‑state achieved in ~1 week. |
| Metabolism | Hepatic (CYP3A4 & CYP2D6) | No major drug interactions with CYP2D6 inhibitors. |
| Excretion | Renal (≈45 %) and fecal (≈55 %) | No dose adjustment for mild‑moderate renal impairment. |
| Peak plasma concentration (Tmax) | 1–2 h (after 0.5 mg dose) | Most common clinical dose. |
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Indications
- Men 40 + yr with moderate‑to‑severe LUTS due to BPH.
- Improves urinary flow rate, decreases post‑void residual, and reduces the need for alpha‑blocker → 5‑alpha‑reductase inhibitor sequential therapy.
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Contraindications
- Hypersensitivity to tamsulosin or any component.
- Severe cardiovascular disease where orthostatic hypotension could precipitate syncope.
- Pregnancy: category C – animal studies show fetal risk; human data lacking.
- Concurrent use of non‑selective alpha blockers (e.g., prazosin) or alpha‑2 agonists can potentiate hypotension.
- Tamsulosin + antihypertensives: increased risk of orthostatic dizziness.
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Dosing
| Dose | Frequency | Administration Notes |
| 0.5 mg | Once daily | Typical start dose. |
| 1.0 mg | Once daily | Optional ↑ if inadequate response. |
| Timing | With or without food | Food may increase absorption; keep intake consistent. |
| Adjunct therapy | May add 5‑alpha‑reductase inhibitor (e.g., finasteride) for > 12 mo in severe BPH. |
• Take at the same time each day to maintain steady‑state levels.
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Monitoring
- Baseline: history of orthostatic symptoms, BP, renal function.
- Follow‑up (4–6 wk):
- Symptom score (IPSS).
- Urine flow rate (Qmax).
- Post‑void residual volume (PVR).
- Blood pressure, especially orthostatic.
- Long‑term: monitor PSA if combining with 5‑α‑reductase inhibitors.
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Clinical Pearls
- Low dose first: 0.5 mg reduces side‑effect profile while providing symptomatic benefit; upgrade only if clinically necessary.
- Timing matters: Take the medication before bedtime if dizziness occurs, as orthostatic hypotension may manifest during the day.
- Fluid intake: Avoid excessive fluid at night to reduce nocturia exacerbation.
- Ejaculation impact: Men may notice decreased ejaculate volume; counsel about possible impact on fertility.
- Drug interactions: Tamsulosin’s CYP3A4 metabolism can be inhibited by ketoconazole or grapefruit pulp → increased serum levels → hypotension.
- Retention risk: In patients with significant residual urine (>50 mL), consider urodynamic studies before initiating therapy.
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