Sildenafil Side Effects
The most common side effects of sildenafil are headache, flushing, dyspepsia (heartburn), nasal congestion, and visual disturbances, which are generally mild to moderate and transient in nature. 1, 2
Common Side Effects
Sildenafil's side effects are primarily related to its vasodilatory properties and typically include:
- Headache (25-30%): Most frequently reported side effect 3
- Flushing (30%): Facial redness and warmth due to vasodilation 3
- Dyspepsia/heartburn (10%): Due to relaxation of the gastroesophageal sphincter 4
- Nasal congestion (19%): Due to vasodilation of nasal blood vessels 3
- Visual disturbances: Including blue-tinged vision, increased light sensitivity, and blurred vision 2
Cardiovascular Side Effects
Sildenafil causes transient reductions in blood pressure that are generally not clinically significant in healthy individuals:
- Mean peak reductions in systolic/diastolic blood pressure of approximately 10/7 mmHg 5
- No significant change in heart rate 5
- Contraindication: Absolutely contraindicated with nitrates in any form due to potentially life-threatening hypotension 6
- Caution: Use with caution in patients with:
- Cardiac failure
- Recent myocardial infarction or stroke (within 6 months)
- Unstable angina
- Uncontrolled hypertension 4
Less Common and Serious Side Effects
- Prolonged visual disturbances: In rare cases, visual disturbances may persist beyond 24 hours, including photophobia, color vision impairment, and impaired visual acuity 7
- Priapism: Erections lasting more than 4 hours requiring immediate medical attention 1
- Sudden hearing loss: Rare but serious side effect 1
- Non-arteritic anterior ischemic optic neuropathy (NAION): Sudden decrease or loss of vision 1
Dose-Related Effects
The incidence of side effects is dose-related, with higher doses associated with increased frequency of adverse events:
- Starting dose is typically 50mg, with adjustments based on efficacy and tolerability 8
- Lower doses (25mg) recommended for elderly patients, those with hepatic or renal impairment, or patients taking CYP3A4 inhibitors 8
Drug Interactions
Sildenafil has important interactions with several medications:
- Nitrates: Absolutely contraindicated due to risk of severe hypotension 6, 1
- Riociguat: Contraindicated due to risk of hypotension 6
- CYP3A4 inhibitors: Medications like ketoconazole, itraconazole, ritonavir, erythromycin, and fluconazole can significantly increase sildenafil levels 6
- Dose reduction recommended when used concurrently with these medications
- Bosentan: Reduces sildenafil levels by approximately 50% 6
Monitoring Recommendations
- Monitor blood pressure when initiating therapy, particularly in patients with cardiovascular risk factors
- Patients should be educated about potential side effects and when to seek medical attention
- Patients with hepatic or renal impairment may require dose adjustments 6
Important Considerations
- Side effects are typically short-lived and mild in nature 3
- The incidence of serious cardiovascular events is not significantly increased in patients without contraindications 5
- Discontinuation rates due to adverse events are low (<3%) 5
- Visual disturbances typically resolve within 21 days in cases of prolonged symptoms 7
When prescribed appropriately and with attention to contraindications, sildenafil has a favorable safety profile with manageable and generally mild side effects.