ED Medications Compared: Sildenafil vs Tadalafil vs Vardenafil vs Avanafil

You've decided to try medication for erectile dysfunction. You open a browser and immediately encounter four options: sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra). They all work through the same mechanism, but they're not identical — and the differences matter more than the marketing suggests.

This is the head-to-head comparison your doctor probably doesn't have time to give you in a 15-minute visit.

How PDE5 Inhibitors Work (All of Them)

All four medications work the same way: they block phosphodiesterase type 5 (PDE5), the enzyme that breaks down cyclic GMP (cGMP) in penile smooth muscle. By blocking this enzyme, they allow cGMP to accumulate, which keeps the smooth muscle relaxed and blood flowing into the penis.

Critical point: PDE5 inhibitors don't create erections on their own. They enhance the natural erectile response that occurs with sexual stimulation. Without stimulation, the drug does nothing. You won't walk around with a spontaneous erection.

Now, the head-to-head comparison.

Sildenafil (Viagra)

The original. FDA-approved in 1998. Over 25 years of data.

• Onset: 30-60 minutes
• Duration: 4-6 hours
• Dosing: 25mg, 50mg, 100mg. Start at 50mg.
• Food interaction: Significant. A high-fat meal delays absorption by up to 1 hour and reduces peak concentration by 29%. Take on an empty stomach for best results, or at least 2 hours after eating.
• Unique characteristics: The most studied PDE5 inhibitor with the longest track record. Available as generic (much cheaper than brand). Also available as Viagra Connect (OTC in some countries).
• Side effects: Headache (16%), flushing (10%), dyspepsia (7%), nasal congestion (4%), visual disturbances — blue-tinged vision (3%) due to cross-reactivity with PDE6 in the retina (unique to sildenafil).
• Best for: Men who want a well-established, affordable on-demand option and don't mind planning around meals.

Tadalafil (Cialis)

The game-changer. FDA-approved in 2003. Changed the conversation with its long duration.

• Onset: 30-60 minutes (some effect as early as 15 minutes)
• Duration: Up to 36 hours — the "weekend pill"
• Dosing:

- On-demand: 10mg or 20mg as needed

- Daily: 2.5mg or 5mg every day for continuous readiness

• Food interaction: Minimal. Can be taken with or without food.
• Unique characteristics:

- The long half-life (17.5 hours) means you don't need to time the dose precisely around sexual activity

- Daily dosing provides continuous erectile readiness — no pill-taking before sex

- Also FDA-approved for BPH/lower urinary tract symptoms — dual benefit for men with both conditions

- Available as generic

• Side effects: Headache (15%), dyspepsia (10%), back pain (6%), myalgia/muscle aches (5%), nasal congestion (3%). The back pain and myalgia are more common with tadalafil than other PDE5 inhibitors.
• Best for: Men who want spontaneity without timing a pill. Men who also have BPH symptoms. Men in relationships with frequent sexual activity (daily dosing). Men who don't want to worry about food.

Vardenafil (Levitra/Staxyn)

The middle ground. FDA-approved in 2003.

• Onset: 30-60 minutes (Staxyn ODT may be slightly faster)
• Duration: 4-6 hours
• Dosing: 5mg, 10mg, 20mg. Start at 10mg. Also available as Staxyn — an orally disintegrating tablet placed on the tongue.
• Food interaction: Moderate. High-fat meals reduce absorption, but less dramatically than sildenafil. Take on a relatively empty stomach when possible.
• Unique characteristics:

- Staxyn (ODT formulation) dissolves on the tongue — no water needed, potentially more discreet

- Slightly more potent PDE5 inhibition than sildenafil at equivalent doses

- QT prolongation potential — avoid in men on class IA or III antiarrhythmics or those with congenital QT prolongation

• Side effects: Headache (15%), flushing (11%), dyspepsia (4%), nasal congestion (9%). Less visual disturbance than sildenafil.
• Best for: Men who want something similar to sildenafil with the option of an orally disintegrating tablet. Men who have visual side effects with sildenafil.

Avanafil (Stendra)

The newest. FDA-approved in 2012. The most selective PDE5 inhibitor.

• Onset: 15-30 minutes — the fastest of the four
• Duration: 6-12 hours (longer than sildenafil/vardenafil but shorter than tadalafil)
• Dosing: 50mg, 100mg, 200mg. Start at 100mg.
• Food interaction: Minimal. Can be taken with or without food. A high-fat meal delays onset slightly but doesn't significantly reduce efficacy.
• Unique characteristics:

- Most PDE5-selective of all four drugs, meaning fewer off-target effects (less PDE6 cross-reactivity = fewer visual effects, less PDE11 cross-reactivity = less myalgia)

- Fastest onset — can work in as little as 15 minutes

- No generic available yet (most expensive option)

• Side effects: Headache (9%), flushing (4%), nasal congestion (3%), back pain (3%). Generally the best side effect profile due to higher selectivity.
• Best for: Men who want fast onset with the fewest side effects. Men who had problematic side effects with other PDE5 inhibitors. Men who need spontaneity but don't want daily dosing.

The Head-to-Head Summary Table

| Feature | Sildenafil | Tadalafil | Vardenafil | Avanafil |

|---------|-----------|-----------|------------|----------|

| Onset | 30-60 min | 30-60 min | 30-60 min | 15-30 min |

| Duration | 4-6 hrs | Up to 36 hrs | 4-6 hrs | 6-12 hrs |

| Food effect | Significant | Minimal | Moderate | Minimal |

| Daily dosing | No | Yes (2.5-5mg) | No | No |

| Generic available | Yes | Yes | Yes | No |

| Treats BPH too | No | Yes | No | No |

| Visual effects | Yes (blue tinge) | Rare | Rare | Rare |

| Back pain/myalgia | Uncommon | Common | Uncommon | Uncommon |

| Cost (generic) | $ | $ | $$ | $$$ |

How to Choose

Choose sildenafil if: You want the most affordable option, you're okay with planning 30-60 minutes ahead, and you can take it without a heavy meal.

Choose tadalafil if: You want spontaneity, you have sex more than twice a week (daily dosing makes sense), you also have BPH/urinary symptoms, or you don't want to think about food timing.

Choose vardenafil if: You want something similar to sildenafil but had visual side effects, or you want the orally disintegrating tablet option.

Choose avanafil if: You want the fastest onset and fewest side effects and cost isn't a primary concern.

What If the First One Doesn't Work?

About 30% of men don't respond adequately to their first PDE5 inhibitor. Before declaring the drug a failure:

1. Try it at least 4-8 times — Response improves with repeated use as anxiety decreases
2. Take it correctly — Empty stomach for sildenafil, adequate time before activity, with sexual stimulation
3. Try the maximum dose — If 50mg sildenafil doesn't work, try 100mg before switching
4. Review medications — Some drugs interact with PDE5 inhibitors or contribute to ED
5. Switch to a different PDE5 inhibitor — Cross-switching works in 30-50% of non-responders. The drugs have different tissue selectivity profiles.

If all PDE5 inhibitors fail, second-line options exist: penile injections, vacuum devices, and surgical implants.

Safety and Interactions

Absolute contraindication: Do not take any PDE5 inhibitor with nitrates (nitroglycerin, isosorbide mononitrate/dinitrate). The combination can cause life-threatening hypotension. This includes recreational use of amyl nitrite ("poppers").

Caution with:

• Alpha-blockers (tamsulosin, doxazosin) — start with the lowest PDE5 inhibitor dose due to additive hypotension
• Antihypertensives — mild additive blood pressure lowering
• CYP3A4 inhibitors (ketoconazole, ritonavir, grapefruit juice) — increase PDE5 inhibitor levels

Getting Started

If you're ready to try ED medication, start with a proper evaluation — not just a prescription. Understanding why you have ED determines which medication and approach will work best.

[Start a visit at coral.clinic/start](https://coral.clinic/start). Dr. Kim provides comprehensive ED evaluation and can prescribe the right PDE5 inhibitor for your specific situation — including helping you switch if the first option doesn't deliver.