Tadalafil Drug Profile

What is Tadalafil?

Tadalafil is a prescription medication belonging to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. It is primarily used to treat erectile dysfunction in men and symptoms of benign prostatic hyperplasia (enlarged prostate). Tadalafil is also approved for treating pulmonary arterial hypertension, a condition affecting blood vessels in the lungs.

Uses

Tadalafil has several FDA-approved medical uses:

• Erectile dysfunction: Helps men achieve and maintain erections sufficient for sexual activity by improving blood flow to the penis
• Benign prostatic hyperplasia (BPH): Relieves urinary symptoms such as difficulty urinating, weak stream, and frequent urination caused by an enlarged prostate
• Combined erectile dysfunction and BPH: Can treat both conditions simultaneously in men who have both diagnoses
• Pulmonary arterial hypertension: Reduces high blood pressure in the arteries of the lungs, improving exercise capacity and slowing disease progression

How it works

Tadalafil works by blocking the enzyme phosphodiesterase type 5 (PDE5), which breaks down a chemical messenger called cyclic GMP. By inhibiting this enzyme, tadalafil allows cyclic GMP levels to remain elevated, leading to smooth muscle relaxation and increased blood flow in targeted areas. This mechanism improves blood flow to the penis during sexual stimulation and relaxes smooth muscle in the prostate and bladder, while also dilating pulmonary blood vessels.

Side effects

Common side effects include:

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• Headache
• Indigestion or upset stomach
• Back pain
• Muscle aches
• Flushing (warmth, redness in face, neck, or chest)
• Stuffy or runny nose
• Dizziness
• Nausea

Serious side effects requiring immediate medical attention:

• Sudden vision loss or changes in vision
• Sudden hearing loss or ringing in ears
• Chest pain or irregular heartbeat
• Erection lasting more than 4 hours (priapism)
• Severe drop in blood pressure causing fainting

Warnings and precautions

• Heart conditions: Men with serious heart problems, recent heart attack, stroke, or life-threatening arrhythmias should not use tadalafil without careful medical supervision
• Blood pressure medications: Patients taking nitrates or alpha-blockers should avoid tadalafil due to risk of dangerous blood pressure drops
• Liver and kidney impairment: Dosage adjustments may be necessary for patients with moderate to severe liver or kidney disease
• Vision problems: Men with retinitis pigmentosa or previous episodes of vision loss should use caution
• Pregnancy category: Not indicated for use in women; effects during pregnancy have not been established

Interactions

Tadalafil has several important drug interactions:

• Nitrates: Can cause life-threatening drop in blood pressure when combined with nitroglycerin or other nitrate medications
• Alpha-blockers: May enhance blood pressure-lowering effects, requiring careful dose timing and monitoring
• CYP3A4 inhibitors: Drugs like ketoconazole, ritonavir, and clarithromycin can increase tadalafil levels, requiring dose reduction
• Blood pressure medications: May enhance hypotensive effects of antihypertensive drugs
• Grapefruit juice: Can increase tadalafil blood levels and should be avoided
• Other PDE5 inhibitors: Should not be used together with sildenafil or vardenafil
• Guanylate cyclase stimulators: Combination with riociguat is contraindicated due to hypotension risk
• Alcohol: Excessive alcohol consumption may increase risk of side effects and reduce effectiveness

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Dosage

Typical adult dosages vary based on the condition being treated:

• Erectile dysfunction (as needed): 10mg taken before sexual activity, may be adjusted to 5mg or 20mg based on effectiveness and tolerance
• Erectile dysfunction (daily use): 2.5mg to 5mg once daily
• Benign prostatic hyperplasia: 5mg once daily
• Pulmonary arterial hypertension: 40mg once daily

Dosage should always be determined by a healthcare provider based on individual medical history, other medications, and response to treatment. Patients with liver or kidney problems may require lower doses.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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