Cialis (tadalafil)
- Name: tadalafil
- Half‑life: ~17.5 hours (range ~14–19 hours)
- Typical dosing:
- On‑demand: 10 mg ~30 minutes before activity (adjust 5–20 mg based on response).
- Daily: 2.5–5 mg once daily for continuous effect.
- Frequency: at most once daily for on‑demand dosing.
- Food: high‑fat meals may slightly delay onset.
- Onset & duration: onset ~30 minutes; duration up to ~36 hours (variable).
- Common side effects: headache, flushing, nasal congestion, dyspepsia, back/muscle pain (more common).
- Serious risks: priapism (>4 hours), sudden vision loss (rare), sudden hearing loss (rare), significant hypotension with nitrates.
- Major interactions/contraindications: absolute contraindication with nitrates; caution with alpha‑blockers, antihypertensives, strong CYP3A4 inhibitors (dose adjustment/avoidance); adjust in severe renal/hepatic impairment.
- Practical notes: preferred when a longer window or daily dosing for spontaneity is desired; muscle/back pain more common; interactions/effects last longer due to long half‑life.
Sildenafil (Viagra)
- Name: sildenafil
- Half‑life: ~3–5 hours
- Typical dosing:
- Usual start: 50 mg ~1 hour before activity (range 25–100 mg).
- Frequency: not more than once every 24 hours.
- Food: high‑fat meals can delay onset.
- Onset & duration: onset 30–60 minutes; duration ~4–6 hours.
- Common side effects: headache, flushing, nasal congestion, dyspepsia, visual disturbances (blue tint) more commonly reported.
- Serious risks: priapism, sudden vision loss (rare), sudden hearing loss (rare), severe hypotension with nitrates.
- Major interactions/contraindications: contraindicated with nitrates; caution with alpha‑blockers and antihypertensives; dose reduction/avoidance with strong CYP3A4 inhibitors and in significant liver/renal impairment.
- Practical notes: well‑studied and commonly used; visual side effects more prominent than with others for some men.
Levitra (vardenafil)
- Name: vardenafil
- Half‑life: ~4–5 hours
- Typical dosing:
- Usual start: 10 mg ~60 minutes before activity (range 5–20 mg).
- Frequency: not more than once every 24 hours.
- Food: high‑fat meals can delay onset; orally disintegrating tablet available in some markets.
- Onset & duration: onset ~30–60 minutes; duration ~4–5 hours.
- Common side effects: headache, flushing, nasal congestion, dyspepsia, dizziness; visual effects less common than sildenafil.
- Serious risks: priapism, rare sudden vision or hearing loss, severe hypotension with nitrates.
- Major interactions/contraindications: contraindicated with nitrates; caution with alpha‑blockers and antihypertensives; dose adjustment with strong CYP3A4 inhibitors and in hepatic/renal impairment.
- Practical notes: similar to sildenafil in onset/duration; some men respond to vardenafil when sildenafil fails; ODT formulation useful for those with swallowing issues.
Shared points (applies to all three)
- Do not combine any with nitrates (risk of severe hypotension).
- Seek urgent care for erection >4 hours, sudden vision/hearing loss, chest pain, or severe adverse effects.
- Generics are available for all three; choice guided by desired duration, side‑effect profile, comorbidities, and drug interactions.