PDE5 inhibitors: What they do and what to watch for

PDE5 inhibitors are the main medicines used for erectile dysfunction (ED) and some lung problems. They work by relaxing blood vessels so blood flows easier to the penis or the lungs. The most common drugs in this group are sildenafil, tadalafil and avanafil. Knowing how they differ and how to use them safely helps you get better results and avoid risks.

How PDE5 inhibitors differ

Sildenafil (often sold as Viagra) usually starts working in 30–60 minutes and lasts about 4–6 hours. Tadalafil (Cialis) can take up to 2 hours to peak, but it lasts much longer—up to 36 hours for the standard dose and daily low-dose options are available. Avanafil often acts fastest, sometimes within 15–30 minutes, and lasts around 6–12 hours. Those timing and duration differences matter when you plan sex or daily dosing.

Effectiveness is similar across them when dosed correctly, but side effects and individual responses vary. Common side effects are headache, flushing, nasal congestion and mild stomach upset. Tadalafil is a bit more linked to muscle or back pain. If you have other health issues—heart disease, low blood pressure, or severe liver or kidney problems—your doctor will pick the best option or adjust the dose.

Safety, interactions and buying advice

Never take a PDE5 inhibitor with nitrates (often used for chest pain). That combo can drop blood pressure very fast and be dangerous. Avoid or be cautious with alpha-blockers, some blood pressure meds, and certain antifungals or antibiotics that change how these drugs are broken down. If you take medicines for HIV, hepatitis C, or some heart drugs, talk to your prescriber—dosage changes may be needed.

If you have chest pain, sudden vision loss, a painful or prolonged erection lasting more than 4 hours, or severe dizziness after taking one of these drugs, seek emergency care. These are rare but real risks.

Thinking of buying PDE5 inhibitors online? Use verified pharmacies that require a prescription. Look for clear contact info, pharmacy certification badges, and a licensed pharmacist available to answer questions. Beware of ultra-cheap offers that don’t ask for a prescription—those pills may be fake or unsafe.

For men with pulmonary arterial hypertension, different PDE5 dosing is used and a specialist should manage care. For ED, start with the recommended initial dose, see how you respond, and adjust under medical guidance. Lifestyle changes—stopping smoking, losing weight, and managing blood sugar—often improve results and may allow lower doses.

If you’re unsure which PDE5 inhibitor fits your routine, talk to your doctor. Tell them about other drugs you take, heart health, and how often you need the medicine. That helps pick the safest, most effective option for you.