Dutasteride/Tamsulosin Drug Interactions: What to Avoid and What to Tell Your Doctor

Dutasteride/tamsulosin (Jalyn) contains two active medications — dutasteride and tamsulosin — each with its own set of drug interactions. Understanding these interactions is important because some combinations can cause dangerous drops in blood pressure, increase your exposure to one of the medications to unsafe levels, or interfere with monitoring your prostate health. This guide covers what you need to know and what to tell your doctor and pharmacist.

Most Important Interaction: PDE5 Inhibitors (ED Medications)

If you take a medication for erectile dysfunction, this is the interaction you most need to know about. Phosphodiesterase type 5 (PDE5) inhibitors include:

Sildenafil (Viagra)

Tadalafil (Cialis)

Vardenafil (Levitra, Staxyn)

Avanafil (Stendra)

Both PDE5 inhibitors and tamsulosin lower blood pressure. When combined, the additive vasodilatory effect can cause a significant, potentially dangerous drop in blood pressure — leading to dizziness, fainting, or even falls. This interaction is particularly risky in older men. If you need to take a PDE5 inhibitor while on dutasteride/tamsulosin, talk to your doctor before combining them. This does not mean they can never be used together, but they must be combined with caution and under medical supervision.

Other Alpha-Blockers

Do not take dutasteride/tamsulosin with other alpha-1 adrenergic blockers. These include:

Alfuzosin (Uroxatral)

Silodosin (Rapaflo)

Doxazosin (Cardura)

Terazosin (Hytrin)

Prazosin (Minipress)

Combining two alpha-blockers significantly increases the risk of low blood pressure (hypotension), which can cause dizziness, fainting, and dangerous falls. Since Jalyn already contains tamsulosin, adding another alpha-blocker is medically inappropriate.

CYP3A4 Inhibitors (Affects Dutasteride and Tamsulosin Levels)

Both dutasteride and tamsulosin are metabolized by the liver enzyme CYP3A4. Drugs that strongly inhibit CYP3A4 can increase blood levels of both components:

Major CYP3A4 inhibitors (use with caution or avoid): Ketoconazole (Nizoral), itraconazole, ritonavir (HIV medication), indinavir

Moderate CYP3A4 inhibitors (use with caution): Verapamil (Calan), diltiazem (Cardizem), fluconazole, erythromycin, clarithromycin, ciprofloxacin, cimetidine

Higher drug levels can amplify side effects, including low blood pressure. If you're prescribed one of these medications, inform your prescriber that you're on dutasteride/tamsulosin. A dose adjustment or closer monitoring may be needed.

CYP2D6 Inhibitors (Affects Tamsulosin Specifically)

Tamsulosin is also metabolized by the CYP2D6 enzyme. Strong CYP2D6 inhibitors can significantly raise tamsulosin blood levels, increasing the risk of blood pressure-related side effects:

Paroxetine (Paxil) — One of the most potent CYP2D6 inhibitors; clinical data shows paroxetine increases tamsulosin's Cmax by 1.3x and AUC by 1.6x.

Fluoxetine (Prozac) — Moderate CYP2D6 inhibitor; use with caution.

Bupropion (Wellbutrin) — Also a moderate CYP2D6 inhibitor; inform your prescriber.

39,333+ patients found their medications in stock

39K+

Find Dutasteride/Tamsulosin In Stock Today →

Blood Pressure Medications (Additive Hypotension Risk)

Any antihypertensive medication can compound the blood-pressure-lowering effect of tamsulosin. This includes:

ACE inhibitors (lisinopril, enalapril)

ARBs (losartan, valsartan)

Calcium channel blockers (amlodipine, nifedipine)

Beta-blockers (metoprolol, atenolol)

Diuretics (furosemide, hydrochlorothiazide)

This interaction is manageable — many men with BPH also have hypertension. Your doctor is likely aware and will monitor you, but it's worth flagging if you're starting any new blood pressure medications.

Warfarin (Blood Thinner)

Caution should be exercised when combining dutasteride/tamsulosin with warfarin (Coumadin). Limited data suggest a possible interaction; your doctor should monitor your INR (blood clotting test) more closely when starting or stopping dutasteride/tamsulosin if you're on warfarin.

Skip the calls, skip the stress.

Find Dutasteride/Tamsulosin In Stock Today →

50K+

Medications
Found

99%

Success
Rate

6+

Hours saved
on average

Food and Supplement Interactions

Grapefruit juice: Grapefruit inhibits CYP3A4 in the gut and can increase both dutasteride and tamsulosin levels. Limit or avoid grapefruit juice while on this medication.

Alcohol: Alcohol can compound tamsulosin's blood pressure-lowering effect, increasing the risk of dizziness and falls. Drink with caution.

Saw palmetto: Some men take saw palmetto for BPH symptoms. Evidence for its effectiveness is mixed, and it should not replace prescribed therapy. Discuss with your doctor before combining.

What to Tell Your Doctor and Pharmacist

Always provide a complete medication list — including OTCs, vitamins, and supplements — to every prescriber and pharmacist. The interactions above don't mean you can never combine these medications, but your care team needs to know to monitor you appropriately. See also our guide to dutasteride/tamsulosin side effects for a full picture of what to watch for.