Tamsulosin

FLOMAX

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Pronunciation: tam-SOO-loe-sin

Tamsulosin ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Tamsulosin ballicule

Tamsulosin FLOMAX mascot mnemonic cartoon — Visual mnemonic: Tamsulosin mascot
**“Tiramisu losin' Flow maximizer”**

What it isAlpha-1A selective antagonist; benign prostatic hyperplasia.

Why this oneUroselective, so it relieves obstruction with less hypotension than the older alpha blockers.

What limits itIntraoperative floppy iris syndrome — the ophthalmologist must be told before cataract surgery. Retrograde ejaculation is common.

Pearls

Highest floppy-iris risk of alpha blockers; stopping beforehand only partly helps.
Take 30 minutes after the same meal daily.

Tamsulosin molecular structure (skeletal formula) — Molecular structure: Tamsulosin

Tamsulosin prescription history

Animated chart of estimated U.S. prescriptions per year, BPH meds (1987–2026). Tamsulosin enters in 1997 (estimated).

FDA-approved for

BPH (1997)

Off-label

ureteral stone passage

Principal riskOrthostatic hypotension and intraoperative floppy iris

Sulfonamide

Sulfonamide-derived drug (non-antibacterial) — label warns

No N4 aromatic amine, no N1 heterocycle: cross-reactivity after a sulfonamide-antimicrobial reaction is unlikely — sulfa-allergic patients reacted to sulfonamide non-antibiotics at 9.9% vs 1.6%, less often than to penicillin. The label warns anyway.

Open the sulfonamide hypersensitivity presentation → · sources [n] are on its References slide.

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryC

Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.

FDA label

Read the full label on DailyMed ↗

NO BOXED WARNINGS

FDA dosing	Population	Start	Target	Max
Benign prostatic hyperplasia (BPH) signs/symptoms	Adults	0.4 mg QD	0.4 mg QD	0.8 mg QD

Titration May increase to 0.8 mg QD after 2-4 weeks if inadequate response to 0.4 mg

Renal Not studied in end-stage renal disease

Hepatic Not studied in severe hepatic impairment

Instructions

Take approximately one-half hour after the same meal each day
Do not crush, chew, or open capsules
If discontinued/interrupted for several days, restart at 0.4 mg QD
Do not use with strong CYP3A4 inhibitors

Available strengths

cap 0.4 mg

Cautions

Postural hypotension / syncope — avoid injury-risk situations
Avoid strong CYP3A4 inhibitors; caution with moderate CYP3A4 or CYP2D6 inhibitors / poor metabolizers
Do not combine with other alpha-blockers
Priapism
Intraoperative Floppy Iris Syndrome — inform ophthalmologist before cataract/glaucoma surgery

Adverse reactions

Headache
Dizziness
Rhinitis
Abnormal ejaculation
Asthenia
Back pain
Diarrhea
Somnolence
Decreased libido
Blurred vision

Pregnancy Not indicated for use in women

Lactation Not indicated for use in women

Cost

Tamsulosin (FLOMAX)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $/mo	CostPlus
0.4 mg	cap	30 qd	$1.50	offered

Generic entry2010

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Memory aids: interaction avatars

CYP3A4 substrate

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Self-check

What should an ophthalmologist know before cataract surgery?
Tamsulosin use, because of floppy iris syndrome.
How does tamsulosin hypotension compare with older alpha blockers?
Less hypotension.