Erectile Dysfunction
April 20, 2026
·
6 min read
read
ED Medications Compared: Sildenafil vs Tadalafil vs Avanafil vs Vardenafil
Title: ED Medications Compared: Sildenafil vs Tadalafil vs Avanafil vs Vardenafil
Title: ED Medications Compared: Sildenafil vs Tadalafil vs Avanafil vs Vardenafil
CTA: ofnoah.sg
If you've been told you have erectile dysfunction (ED), your doctor has almost certainly mentioned a PDE5 inhibitor. Four are currently available in clinical practice: sildenafil (Viagra), tadalafil (Cialis), avanafil (Stendra/Spedra), and vardenafil (Levitra). They share a mechanism of action, but they are meaningfully different drugs — and choosing the right one matters.
This article compares all four across the dimensions that matter most in real-world use: how fast they work, how long they last, how food and alcohol affect them, their side-effect profiles, and who each drug is best suited for.
Medical disclaimer: This article is for informational purposes only. It does not constitute medical advice. Speak to a licensed physician before starting any ED medication.
Sexual arousal triggers nitric oxide (NO) release in penile tissue. NO activates an enzyme that produces cyclic guanosine monophosphate (cGMP), which relaxes smooth muscle and increases blood flow, producing an erection. Phosphodiesterase type 5 (PDE5) breaks down cGMP, ending the erection.
PDE5 inhibitors block PDE5, prolonging the effect of cGMP and supporting erection in response to sexual stimulation. Critically, they do not cause erections independently — arousal is still required.[1]
All four drugs in this class are prescription-only medications. In Singapore, they are regulated by the Health Sciences Authority (HSA) and require a valid prescription.
| Sildenafil | Tadalafil | Avanafil | Vardenafil | |
|---|---|---|---|---|
| Brand name | Viagra | Cialis | Stendra / Spedra | Levitra |
| Onset | 30–60 min | 30–60 min | 15–30 min | 25–60 min |
| Duration | 4–6 hours | Up to 36 hours | 4–6 hours | 4–6 hours |
| Food interaction | High-fat meal delays | Minimal | Minimal | High-fat meal delays |
| Available as daily dose | No | Yes (2.5–5 mg) | No | No |
| Approved for BPH+ED | No | Yes | No | No |
Sildenafil was the first PDE5 inhibitor approved by the US FDA (1998) and remains the most widely studied ED medication in the world.[2] It is available as 25 mg, 50 mg, and 100 mg oral tablets, with 50 mg typically the starting dose.
Onset and duration: Most men experience onset within 30–60 minutes. The window of effectiveness is roughly 4–6 hours, though this varies by individual metabolism.
Food interaction: A high-fat meal significantly delays and reduces sildenafil absorption. For reliable results, it should be taken on an empty stomach or after a light meal.
Side effects: The most commonly reported side effects are headache, facial flushing, nasal congestion, dyspepsia, and — at higher doses — transient visual disturbances (a blue-tinged hue or increased light sensitivity). These are generally mild and transient.[2]
Who it suits: Men who prefer a well-studied, cost-accessible option with an established clinical track record. Particularly suitable when timing is somewhat predictable.
Tadalafil is distinguished by its dramatically longer half-life — approximately 17.5 hours — giving it an effective window of up to 36 hours. This has earned it the nickname "the weekend pill."[3] It is available in on-demand doses (10 mg and 20 mg) or as a daily low-dose option (2.5 mg or 5 mg).
Onset and duration: Onset is similar to sildenafil at 30–60 minutes, but the extended window means dosing pressure is significantly lower. Men who take the daily dose can achieve a steady-state plasma level that provides readiness without planning around a pill.
Food interaction: Tadalafil can be taken with or without food, including high-fat meals, without meaningful impact on absorption — a practical advantage.
Additional indication: Tadalafil is the only PDE5 inhibitor approved to treat both ED and benign prostatic hyperplasia (BPH), making it a useful option for men dealing with both conditions simultaneously.[3]
Side effects: Back pain and myalgia (muscle aches) are reported more frequently with tadalafil than with other PDE5 inhibitors — a consequence of PDE11 inhibition, which is more pronounced with this compound. Headache and flushing occur but tend to be less intense than with sildenafil.[4]
Who it suits: Men who want flexibility without timing pressure, or those who prefer the low-dose daily regimen for a more "spontaneous" experience.
Avanafil is the newest approved PDE5 inhibitor, with FDA approval granted in 2012. It was developed to address two limitations of earlier drugs: slow onset and cardiovascular safety in specific populations.[5]
Onset and duration: Clinical trials show avanafil can be effective in as little as 15–30 minutes in many patients — significantly faster than other options. Duration is comparable to sildenafil at 4–6 hours.
Food interaction: Minimal. Food does not meaningfully affect avanafil absorption, which contributes to its convenience profile.
Selectivity: Avanafil has a higher selectivity for PDE5 over other PDE isoforms (particularly PDE6, which mediates the visual side effects seen with sildenafil). This contributes to a cleaner side-effect profile at therapeutic doses.[5]
Side effects: Headache, flushing, and nasal congestion occur, but the incidence of visual disturbances is very low. Cardiovascular safety data in patients with stable cardiovascular disease is also notably good compared to earlier compounds.
Who it suits: Men who want the fastest onset available, particularly for less-planned encounters; men who have experienced bothersome visual side effects with sildenafil.
Vardenafil was approved by the FDA in 2003 and shares much of sildenafil's pharmacokinetic profile — onset, duration, and food sensitivity are similar.[6] It is available in 5 mg, 10 mg, and 20 mg doses. An orally disintegrating formulation (Staxyn) is available in some markets.
Onset and duration: 25–60 minutes onset, 4–6 hours effective window.
Food interaction: A high-fat meal delays absorption — similar to sildenafil. Take on an empty or light-meal stomach for best results.
Selectivity: Vardenafil has higher PDE5 selectivity than sildenafil, which may translate to slightly fewer off-target effects in some patients. However, it does have a greater effect on QTc interval prolongation than other PDE5 inhibitors, and is contraindicated with certain antiarrhythmic medications.[6]
Side effects: Similar to sildenafil: headache, flushing, nasal congestion, dyspepsia. Visual disturbances are less common than with sildenafil.
Who it suits: Men who haven't tolerated sildenafil well and are looking for a similar but slightly differentiated option; men who prefer an orally disintegrating format.
Timing and spontaneity: If planning around a pill is frustrating, tadalafil (either 36-hour or daily dosing) or avanafil (fast onset) offer the most flexibility.
Dietary habits: If you frequently eat high-fat meals, tadalafil or avanafil are more forgiving than sildenafil or vardenafil.
Side-effect sensitivity: Men bothered by visual disturbances from sildenafil may prefer avanafil or vardenafil. Men who develop back/muscle aches should note that this is more common with tadalafil.
Comorbidities: Men with both ED and BPH may benefit specifically from tadalafil's dual indication. Men on antiarrhythmics should note vardenafil's QTc effect. All four are contraindicated with nitrate medications (e.g., glyceryl trinitrate) — this is an absolute contraindication regardless of drug choice.
Trial and adjustment: It often takes more than one attempt to establish effective dosing. Clinical guidelines recommend at least 4–6 attempts before concluding a drug isn't effective for a given patient.[7]
Q: Which ED medication works fastest?
Avanafil has the fastest onset, with some patients reporting effects within 15 minutes. Sildenafil and tadalafil typically take 30–60 minutes.
Q: Which ED drug lasts the longest?
Tadalafil — up to 36 hours, versus 4–6 hours for the other three.
Q: Can I take ED medication with alcohol?
Moderate alcohol (1–2 drinks) is generally considered acceptable, but alcohol is itself a cause of erectile dysfunction and can reduce the drug's effectiveness. High alcohol intake combined with PDE5 inhibitors can cause significant blood pressure drops.
Q: Is there a generic version of these medications?
Generic sildenafil and generic tadalafil are widely available. Generic avanafil and vardenafil availability varies by market.
Q: Are these medications safe for everyone?
No. PDE5 inhibitors are contraindicated with nitrates, certain alpha-blockers, and in men with severe cardiovascular disease. A doctor must assess suitability before prescribing.
Q: Do I need a prescription?
Yes — in Singapore, all four PDE5 inhibitors are prescription-only medications regulated by the Health Sciences Authority.
Noah offers clinician-reviewed ED treatment online — discreet, convenient, and delivered to your door.
If you're ready to speak with a licensed doctor about which ED medication is right for you, Noah makes it straightforward. Answer a health questionnaire, consult a Singapore-registered physician, and receive your prescription with fast, private delivery.
Start your consultation at ofnoah.sg →
Noah is not a pharmacy. Prescriptions are issued solely at the discretion of our partner physicians following clinical assessment.
