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Tamsulosin (Flomax)

Alpha Blockerprescriptionoral · inferred

Selective alpha-1A adrenergic receptor antagonist used for benign prostatic hyperplasia (BPH) and as medical expulsive therapy for distal ureteral stones. Relaxes prostatic smooth muscle with less systemic hypotension than older non-selective alpha-blockers. 0.4-0.8 mg PO daily 30 min after the same meal. Fasted bioavailability >90%; reduced by food. Intraoperative floppy iris syndrome reported in cataract surgery.

Projected serum levels — 0.40 mg, once daily

Tamsulosin (Flomax)
Tamsulosin (Flomax) modeled serum levels, 0.40 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 2 days. 0 0.25 0.50 0.75 1 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 2
Tamsulosin (Flomax) modeled serum levels with a loading dose of 0.59 mg, then 0.40 mg once daily The first dose is larger so levels approach steady state faster. 0 0.25 0.50 0.75 1 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 0.40 mg once daily (oral).

Loading schedule: 0.59 mg on day 1, then 0.40 mg once daily — reaching therapeutic levels sooner.

Modeled steady state after ~2 days: peak ≈ 0.42 mg, trough ≈ 0.17 mg body load. Population-based estimate over 15 days for a 0.40 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Alpha Blocker
Route modeled
Oral
Model confidence
inferred
Half-life
14 h
Common dose
0.40 mg
Suggested maximum
0.80 mg/day
Reference dose range
0.20–0.80 mg (single dose)
Suggested cadence
once daily
Validated against
0.40 mg oral — Cmax 0.010 mg/L at 5 h

Documented interactions

  • danger
    Carbamazepine (Tegretol) + Tamsulosin (Flomax) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Tamsulosin (Flomax) AUC by ~0.31x

  • danger
    Clarithromycin (Biaxin) + Tamsulosin (Flomax) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Tamsulosin (Flomax) AUC by ~2.00x

  • danger
    Diltiazem + Tamsulosin (Flomax) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Tamsulosin (Flomax) AUC by ~2.00x

  • danger
    Efavirenz (Sustiva) + Tamsulosin (Flomax) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Tamsulosin (Flomax) AUC by ~0.20x

  • danger
    Grapefruit (whole fruit) + Tamsulosin (Flomax) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Tamsulosin (Flomax) AUC by ~2.00x

  • danger
    Grapefruit Juice + Tamsulosin (Flomax) CYP inhibition

    Grapefruit Juice mechanism_based of CYP3A4 predicted to change Tamsulosin (Flomax) AUC by ~2.00x

Serum checks 98 modeled interaction pairings for tamsulosin (flomax) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Clinical pharmacokinetics of tamsulosin van Hoogdalem EJ et al. · European Urology, 1997 DOI

    PK review establishing tamsulosin's ~12h half-life, food-reduced bioavailability, and alpha-1A selectivity underpinning its BPH efficacy.

  2. Tamsulosin: a review of its pharmacology and therapeutic efficacy in the management of symptomatic benign prostatic hyperplasia Wilde MI, McTavish D · Drugs, 1996 DOI

    Foundational therapeutic review summarizing tamsulosin's efficacy, safety, and differentiation from non-selective alpha-blockers in BPH.

2 published studies referenced in the app, each with a plain-language summary.