How To Use Sildenafil
Complete Step-by-Step Usage Guide, Dosage Instructions & Safety Information
Key Takeaways: How to Use Sildenafil Safely
- Optimal Timing: Take 30-60 minutes before sexual activity
- Starting Dose: 50mg is standard, adjust based on response and tolerability
- Frequency: Maximum once every 24 hours
- Food Effect: Take on empty stomach for fastest onset (1 hour delay with high-fat meal)
- Essential Requirement: Sexual stimulation needed for medication to work
- Absolute Contraindication: Never take with nitrate medications (dangerous blood pressure drop)
Sildenafil requires proper timing and administration to work effectively for erectile dysfunction. Following the correct usage guidelines ensures you get the maximum benefit while minimising potential side effects and risks.
Emergency Medical Warning
If you experience chest pain, an erection lasting more than 4 hours (priapism), sudden vision loss, or severe allergic reaction while taking sildenafil, seek immediate medical attention. Do not take sildenafil with nitrate medications.
How to Take Sildenafil: Step by Step Usage Guide
Following these steps ensures you use sildenafil correctly and safely for optimal results in treating erectile dysfunction.
Consultation & Prescription
Speak with a UK-registered doctor who will assess your suitability for sildenafil. Never use sildenafil without a proper prescription, as it requires medical evaluation of your heart health and medication interactions.
Dose Selection
Start with the prescribed dose (usually 50mg). Your doctor may recommend starting with 25mg if you're over 65, have liver or kidney problems, or are taking certain other medications.
Timing & Planning
Take sildenafil approximately 30-60 minutes before planned sexual activity. The medication typically remains effective for 4-6 hours after taking, but works best within the first few hours.
Administration
Swallow the tablet whole with a glass of water. Do not crush, chew, or break the tablet. Sildenafil can be taken with or without food, but avoid heavy, high-fat meals before taking.
Sexual Stimulation
Remember that sildenafil requires sexual stimulation to work. The medication enhances your body's natural response but doesn't cause an erection spontaneously.
Dose Adjustment
If 50mg is too strong or causes side effects, reduce to 25mg. If ineffective, your doctor may increase to 100mg. Never take more than 100mg in 24 hours.
🗒️ Important Reminder: Sildenafil should only be taken once per day. Taking more frequent doses won't increase effectiveness and significantly increases the risk of side effects. If a dose doesn't work as expected, wait until the next day to try again.
Sildenafil Dosage Guide
Sildenafil comes in three strengths: 25mg, 50mg, and 100mg tablets. The correct dose depends on your individual response, tolerance, and medical circumstances.
Standard Dosage Recommendations
| Dose Strength | Recommended For | Timing & Frequency | Maximum Effect |
|---|---|---|---|
| 25mg | Elderly (≥65), liver/kidney impairment, those on CYP3A4 inhibitors | 30-60 mins before activity, once daily max | Mild to moderate ED, good for first-time users testing tolerance |
| 50mg | Most adults with ED (standard starting dose) | 30-60 mins before activity, once daily max | Effective for majority of ED cases, balanced efficacy/safety |
| 100mg | When 50mg ineffective, severe ED cases (doctor's advice only) | 30-60 mins before activity, once daily max | Maximum therapeutic effect, higher side effect risk |
Dosage Adjustment Scenarios
If Dose is Too Strong
- Experiencing headaches, flushing, indigestion
- Vision changes (blue tint, light sensitivity)
- Dizziness or nasal congestion
- Action: Reduce to next lower dose
If Dose is Too Weak
- Insufficient erection for sexual activity
- Erection doesn't last long enough
- No noticeable effect after 1 hour
- Action: Consult doctor about increasing dose
If No Effect at All
- No improvement after 2-3 attempts
- Remember: Requires sexual stimulation
- May need different ED treatment
- Action: Consult doctor for reassessment
🗒️ Dosage Warning: Never exceed 100mg in 24 hours. Higher doses don't increase efficacy and significantly raise the risk of serious side effects including priapism (painful prolonged erection), severe hypotension, and vision changes.
Who Should Use Sildenafil
Sildenafil is specifically designed for certain individuals with erectile dysfunction and should only be used under medical supervision.
Appropriate Candidates for Sildenafil
Primary Indication
Adult men with erectile dysfunction - difficulty achieving or maintaining an erection sufficient for satisfactory sexual activity.
Age Group
Men aged 18 years and older - Not approved for use in children or adolescents.
ED Causes
Suitable for ED from various causes: psychological, vasculogenic, diabetes-related, or mixed etiology.
Medical Evaluation Requirements
| Assessment Needed | Reason | Typical Evaluation |
|---|---|---|
| Cardiovascular Health | Sildenafil affects blood pressure; heart must withstand sexual activity | Blood pressure check, heart history, stress test if indicated |
| Current Medications | Dangerous interactions with nitrates and some other drugs | Complete medication review including over-the-counter medicines |
| ED Underlying Cause | To ensure appropriate treatment and rule out reversible causes | Medical history, possible blood tests (testosterone, glucose) |
| Vision Assessment | Rare risk of vision changes, especially with pre-existing eye conditions | Discussion of eye health history, particularly NAION risk factors |
🗒️ Clinical Insight: Good candidates for sildenafil typically have at least some intact nitric oxide production (needed for the medication to work). Those with severe nerve damage or very poor blood flow may respond less effectively.
Who Should Not Use Sildenafil
Certain individuals must absolutely avoid sildenafil due to potentially life-threatening risks and complications.
Absolute Contraindications
Nitrate Users
Absolute prohibition with any nitrate medication (for angina) or recreational poppers (amyl nitrite). Combination causes dangerous blood pressure drop.
Rictoiguat Users
Contraindicated with rictoiguat (for pulmonary hypertension). Combined use can cause severe hypotension.
Recent Cardiovascular Events
Avoid if recent heart attack, stroke, or life-threatening arrhythmia. Sexual activity may strain compromised cardiovascular system.
Additional Precautions and Warnings
| Condition | Risk Level | Precaution Needed |
|---|---|---|
| Severe Liver Impairment | High | Maximum 25mg dose, close monitoring required |
| Severe Kidney Impairment | High | Maximum 25mg dose, creatinine clearance <30 mL/min |
| Hypotension (low blood pressure) | High | Sildenafil may further lower blood pressure |
| Hypertension (high blood pressure) | Medium | Ensure blood pressure controlled before use |
| Anatomical Penile Deformity | Medium | Risk of priapism; includes Peyronie's disease |
| Bleeding Disorders | Medium | Increased bleeding risk (e.g., haemophilia) |
| Stomach Ulcers | Medium | May exacerbate gastrointestinal bleeding |
| Retinitis Pigmentosa | Medium | Genetic eye disorder - use with extreme caution |
🗒️ Safety Alert: Sildenafil is not for use by women, children, or men without erectile dysfunction. Using it recreationally or for enhancement without medical need is dangerous and medically inappropriate.
To Be Taken With or Without Food
Food significantly affects how quickly sildenafil starts working, but doesn't prevent it from working eventually.
How Food Affects Sildenafil Absorption
Empty Stomach (Recommended)
Onset Time: 30-60 minutes
Peak Concentration: Maximum absorption
Effectiveness: Optimal
Best For: Fastest results, predictable timing
With Light Meal
Onset Time: 45-75 minutes
Peak Concentration: Slightly reduced
Effectiveness: Good
Best For: Those prone to stomach upset
With High-Fat Meal
Onset Time: Delayed by 1+ hours
Peak Concentration: Reduced by 30%
Effectiveness: Reduced and unpredictable
Recommendation: Avoid for optimal results
Food Interaction Guidelines
| Food Type | Effect on Sildenafil | Recommendation |
|---|---|---|
| High-fat meals (burgers, chips, fried foods) | Delays absorption by 60+ minutes, reduces peak concentration by 30% | Avoid within 2 hours of taking sildenafil |
| Light meals (sandwich, salad, fruit) | Minimal delay (15-30 minutes), slight absorption reduction | Acceptable if needed to prevent stomach upset |
| Grapefruit juice | Inhibits metabolism, increases sildenafil levels and side effect risk | Avoid completely on days taking sildenafil |
| Alcohol | Can impair erection ability, increases dizziness and blood pressure drop risk | Limit alcohol, avoid excessive consumption |
🗒️ Practical Tip: If you've eaten a heavy meal and need to take sildenafil, wait at least 2 hours after eating, or plan sexual activity for 2-3 hours after taking the medication to allow for delayed absorption.
Special Conditions: Pregnancy, Breastfeeding & Other Considerations
While sildenafil is not indicated for women, understanding its use in special populations and conditions is important for comprehensive patient care.
Pregnancy and Breastfeeding
Pregnancy Category
Not indicated for use in women - Sildenafil is not approved for use during pregnancy. Some specialised hospital settings may use it for specific pregnancy-related conditions under close supervision, but this is not relevant for ED treatment.
Breastfeeding
Not indicated for use in women - Since sildenafil is not prescribed to women for erectile dysfunction, breastfeeding considerations don't apply. However, if accidentally ingested by a breastfeeding woman, consult a doctor immediately.
Other Special Considerations
| Special Condition | Consideration | Recommendation |
|---|---|---|
| Elderly (≥65 years) | Reduced clearance, increased sensitivity | Start with 25mg dose, monitor closely for side effects |
| Hepatic Impairment | Reduced metabolism, increased exposure | Severe impairment: max 25mg; mild-moderate: consider 25mg starting dose |
| Renal Impairment | Reduced elimination, increased exposure | Creatinine clearance <30 mL/min: max 25mg; 30-50 mL/min: consider 25mg start |
| Diabetes | May have reduced response due to neuropathy/vascular changes | May require higher dose (100mg), monitor blood glucose effects |
| Prostate Problems | Alpha-blockers interaction risk | Separate doses by 4+ hours if taking alpha-blockers for prostate |
| Driving & Machinery | May cause dizziness, visual disturbances | Don't drive/operate machinery until you know how it affects you |
Lactose and Sodium Content
Lactose Content
Sildenafil tablets contain lactose monohydrate. If you have lactose intolerance or galactose intolerance, consult your doctor before use.
Sodium Content
Each tablet contains less than 1 mmol sodium (23 mg), which is essentially 'sodium-free' and suitable for low-sodium diets.
🗒️ Storage Information: Store sildenafil at room temperature (15-30°C), in original packaging, away from moisture and direct sunlight. Keep out of sight and reach of children. Do not use after expiry date printed on packaging.
Sildenafil Usage FAQs
How long before sex should I take sildenafil?
Take sildenafil 30-60 minutes before planned sexual activity. If taken on an empty stomach, it may work in 30 minutes; with a heavy meal, it could take 2 hours. The effects typically last 4-6 hours.
Can I take sildenafil every day?
No, sildenafil should not be taken daily for erectile dysfunction. Maximum frequency is once per 24 hours. Daily use is only for specific pulmonary hypertension treatment with different dosing.
What should I do if sildenafil doesn't work?
If ineffective after 2-3 attempts: 1) Ensure sexual stimulation, 2) Take on empty stomach, 3) Try different timing, 4) Consult your doctor about dose adjustment or alternative treatments.
Can I cut sildenafil tablets in half?
Tablets should be swallowed whole with water. However, if prescribed a lower dose, your doctor can prescribe the appropriate strength. Don't split tablets unless advised by your doctor.
Is it safe to drink alcohol with sildenafil?
Limit alcohol as it can impair erection ability and increase side effects like dizziness and blood pressure drops. Heavy drinking with sildenafil is not recommended.
Ready to Start Sildenafil Treatment?
If you're experiencing erectile dysfunction and believe sildenafil could help, speak with a UK-registered doctor through our confidential online consultation service. Get genuine medication with proper medical supervision.
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Medical Content Manager
Nabeel is a co-founder, and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder, and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 20 January 2024
Next Review: 20 July 2024
Published on: 20 January 2024
Last Updated: 20 January 2024
