Sildenafil (Viagra) in Singapore: Dosage, Side Effects, Cost & How to Get It

Medically reviewed by Dr. Kevin Chua, Medical Director

Disclaimer: This article provides general medical information and is not a substitute for professional medical advice. Sildenafil is a prescription-only medication in Singapore. Always consult a licensed doctor before use.

Introduction

Sildenafil — marketed as Viagra and available in multiple generic forms — was the first oral medication approved for erectile dysfunction (ED) and remains one of the most prescribed treatments worldwide. Since its approval in 1998, it has been used by tens of millions of men with a well-established safety record¹.

This guide covers everything Singaporean men need to know about sildenafil: how it works, correct dosing, what side effects to expect, how much it costs in Singapore, and how to get a legitimate prescription.

How Sildenafil Works

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor. To understand how it works, it helps to understand the mechanics of erection.

During sexual arousal, nerves in the penis release nitric oxide (NO). This triggers production of a chemical called cyclic GMP (cGMP), which relaxes the smooth muscle in the penile arteries and allows blood to flow in, producing an erection. PDE5 is the enzyme responsible for breaking down cGMP. By inhibiting PDE5, sildenafil allows cGMP to accumulate, enhancing the natural erectile response¹.

Key point: Sildenafil does not create an erection on its own. It enhances the body's natural response to sexual stimulation. Without arousal, the medication will not produce an erection.

Dosage Guide

Sildenafil is available in 25 mg, 50 mg, and 100 mg tablets. The right dose depends on your individual response and tolerability, determined during your consultation.

Standard Dosing

How to Take It

• Take 30–60 minutes before anticipated sexual activity
• On an empty stomach or after a light meal — high-fat meals significantly delay absorption
• Maximum one dose per day
• Do not split or crush extended-release formulations (standard tablets may be split if scored)

Tips for Best Results

• Give sildenafil at least 4–6 attempts before concluding it doesn't work — initial doses may not produce optimal results
• Avoid heavy meals and excessive alcohol before taking it
• Allow adequate sexual stimulation — foreplay matters
• If 50 mg doesn't work after several attempts, your doctor may increase to 100 mg

Side Effects

Most side effects are mild to moderate and diminish with continued use. They result from PDE5 inhibition in other tissues (blood vessels, sinuses, retina).

Common Side Effects (>10% of users)

• Headache — the most common side effect, caused by vasodilation
• Facial flushing — warmth or redness in the face and neck
• Nasal congestion — due to vasodilation in nasal mucosa

Less Common Side Effects (1–10%)

• Dyspepsia (indigestion)
• Visual disturbances — mild blue tinge to vision, increased light sensitivity (temporary)
• Dizziness

Rare but Serious Side Effects

• Priapism — an erection lasting more than 4 hours. Seek emergency medical attention immediately
• Sudden hearing loss — rare; discontinue and seek medical care
• Non-arteritic anterior ischaemic optic neuropathy (NAION) — extremely rare; more associated with pre-existing risk factors

If you experience any serious side effects, contact your doctor or visit an emergency department immediately.

Contraindications and Interactions

Sildenafil must not be used in certain situations due to safety risks.

Absolute Contraindications

• Nitrate medications (GTN spray, isosorbide mononitrate/dinitrate) — combination can cause life-threatening hypotension¹
• Severe cardiovascular disease — recent MI or stroke (within 6 months)
• Severe hepatic impairment
• Hypotension (BP <90/50 mmHg)

Drug Interactions

• Alpha-blockers (e.g., tamsulosin for BPH) — may cause postural hypotension; use lowest sildenafil dose
• CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, erythromycin) — increase sildenafil blood levels; reduce dose to 25 mg
• Other PDE5 inhibitors — do not combine
• Grapefruit juice — may modestly increase blood levels

Cost of Sildenafil in Singapore

Sildenafil is one of the most affordable ED treatments available, especially in generic form.

Price Comparison (SGD)

Prices are approximate and may vary by provider. Updated April 2026.

Are Generics as Effective?

Yes. Generic sildenafil contains the same active pharmaceutical ingredient in the same dose and must meet HSA bioequivalence standards. Multiple clinical studies have confirmed equivalent efficacy¹.

How to Get Sildenafil in Singapore

Sildenafil is a prescription-only medication in Singapore. You cannot legally purchase it without a doctor's prescription. Here's how to access it:

Through noah™ (Online)

1. Complete an online health questionnaire
2. An SMC-registered doctor reviews your assessment
3. If appropriate, a prescription is issued
4. Medication is delivered discreetly to your address

Through a GP or Polyclinic

Visit in person. Consultation fees typically range from S$30–80, plus medication costs.

Through a Urologist

For complex cases. Specialist fees range from S$150–350.

Warning: HSA regularly seizes counterfeit or adulterated sexual enhancement products sold online or at unauthorised retailers. These products may contain dangerous levels of active ingredients or harmful contaminants. Always obtain sildenafil through a legitimate medical channel.

FAQ

1. How long does sildenafil last?

Sildenafil's effects typically last 4–6 hours. Some men report effects up to 8 hours, but this varies by individual. Peak blood levels occur approximately 1 hour after dosing.

2. Can I take sildenafil every day?

Sildenafil is designed for on-demand use (as needed, before sexual activity). Daily dosing of sildenafil is not standard practice — for continuous coverage, tadalafil 5 mg daily is the usual recommendation. → See: Tadalafil Guide (SG-N-ED-03)

3. What happens if I take sildenafil and don't need it?

If you take sildenafil but don't engage in sexual activity, you may experience mild side effects (headache, flushing) but no erection — sexual stimulation is required. The medication will be metabolised normally.

4. Can I drink alcohol with sildenafil?

Moderate alcohol (1–2 standard drinks) is generally safe. Excessive alcohol can worsen ED symptoms and increase the risk of side effects like dizziness and low blood pressure. For best results, limit alcohol use.

5. Is it safe to order sildenafil from overseas websites?

We strongly advise against it. Products from unregulated sources may be counterfeit, contain incorrect doses, or include dangerous contaminants. HSA has issued multiple warnings about illegal ED products. noah™ provides HSA-registered medications dispensed through licensed pharmacies.

References

→ Return to pillar: Complete Guide to ED Treatment in Singapore

This article is for informational purposes only and does not constitute medical advice. Always consult a licensed doctor before starting any treatment. noah™ consultations are conducted by SMC-registered doctors in accordance with MOH telemedicine guidelines.