Sildenafil vs. tadalafil: which is better for ED?

When comparing sildenafil vs. tadalafil for erectile dysfunction (ED), the main differences are how long each medication lasts and how it is taken. Sildenafil is the active ingredient in Viagra, and tadalafil is the active ingredient in Cialis. Both are PDE5 inhibitors, a type of medication that boosts blood flow to help get and maintain an erection.

Neither medication is better for everyone. Sildenafil is typically taken as needed about an hour before sex and lasts around 4–6 hours, while tadalafil can be taken as needed or daily and lasts up to 36 hours. The difference between sildenafil and tadalafil often comes down to lifestyle, how often a person has sex, and how much flexibility they want with timing. A healthcare provider can help determine which option is the better fit.

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Choose sildenafil if:

• You prefer to take ED medication only when you need it, rather than every day.

• You typically plan sexual activity ahead of time and do not mind taking a pill about 30–60 minutes beforehand. It can also be taken up to 4 hours before.

• You want a shorter window of effectiveness. Sildenafil typically lasts around 4–6 hours, which may be a good fit if you do not need all-day coverage.

• You are comfortable timing your dose around meals, since high-fat meals can delay how quickly sildenafil starts working.

Choose tadalafil if:

• You want more spontaneity. Tadalafil can stay active in your body for up to 36 hours, giving you a much wider window for sexual activity without having to plan as carefully.

• You prefer the convenience of a daily pill. Low-dose tadalafil can be taken every day, so you do not have to think about timing medication before sex.

• You do not want meals to affect your medication. Both sildenafil and tadalafil can be taken with or without food, but taking sildenafil with a high fat meal can delay when it starts working.

• You also have symptoms of benign prostatic hyperplasia (BPH), or enlarged prostate, such as frequent urination. Daily tadalafil is FDA-approved to treat both ED and BPH symptoms.

Sildenafil vs. tadalafil: which works faster?

Sildenafil starts working in about 30–60 minutes and tadalafil in about 30 minutes, but sildenafil’s onset can be delayed by a high-fat meal.

Sildenafil is usually taken about an hour before sex, though it can be taken anywhere from 30 minutes to four hours beforehand.

Tadalafil also begins working within about 30 minutes and is not affected by food. Its effects can last up to 36 hours, which allows a wider window for sexual activity.

People prescribed daily tadalafil do not need to time doses around planned sexual activity. Taking it at about the same time each day helps maintain steady levels.

Sildenafil vs. tadalafil: which lasts longer?

Tadalafil lasts up to 36 hours — much longer than sildenafil, which works for about 4–6 hours.

Because sildenafil provides a shorter window of effectiveness, it may be a better fit for planned sexual activity. ED medication should be taken as prescribed and no more than once per day.

Tadalafil, on the other hand, can stay active for up to 36 hours, so there is less need to plan timing as carefully. Its lower doses also come as a daily option, which keeps a steady amount in your system so you can be ready whenever the moment feels right.

Sildenafil vs. tadalafil: cost comparison 

With discounts, generic sildenafil (100 mg) typically costs about $0–$22 for 30 tablets, and generic tadalafil (5 mg) typically costs about $0–$27.

Without insurance or discounts, the cash price can climb as high as $191 for sildenafil and $97 for tadalafil. Savings programs and coupons from pharmacy discount sites can make both medications much more affordable. Generic sildenafil and tadalafil are also available on Ro, with prices that vary by dose and plan.

The brand-name versions of Viagra and Cialis are far pricier, often costing as much as $550 and $315, respectively, depending on location, even with discounts.

Sildenafil vs. tadalafil: dosage and schedules 

Healthcare providers typically start sildenafil at 50 mg and may adjust the dose to 25 mg or 100 mg, taken as needed about an hour before sex. Tadalafil typically starts at 10 mg as needed (adjusted to 5 mg or 20 mg) or 2.5 mg daily (increased to 5 mg if needed).

Starting doses can vary based on factors such as age, liver or kidney conditions, and other medications. Following a healthcare provider’s instructions closely is important.

Sildenafil should be taken no more than once in a 24-hour period, about 30–60 minutes before sexual activity. A healthcare provider may adjust the dose if side effects occur.

Tadalafil comes in several strengths: 2.5 mg, 5 mg, 10 mg, and 20 mg tablets. It can be taken as needed or, at the lower doses, daily to maintain steady levels in the body. The maximum is 20 mg as needed, no more than once per day, or 5 mg when taken daily.

Research suggests sildenafil and tadalafil are both generally safe and effective for treating ED. Research also suggests that many people prefer tadalafil, possibly because it lasts longer, allows for more spontaneity, and may support sexual confidence.

Sildenafil side effects

Common side effects of sildenafil include:

• Headache

• Facial flushing

• Indigestion

• Nasal congestion

• Dizziness

• Visual changes (such as a blue tint or other color disturbances)

Sildenafil side effects are often mild and short-lived. Still, anyone who has serious symptoms — especially an erection lasting longer than four hours — should get medical help right away.

Sildenafil should not be used with nitrates (such as nitroglycerin for chest pain) or nitrites (“poppers”), because the combination can make blood pressure dangerously low. It also should not be used with guanylate cyclase stimulators, such as riociguat.

Sildenafil can interact with other medications as well. Before starting sildenafil, a healthcare provider can help determine whether it is safe, especially for people with heart, circulation, or blood pressure issues.

Tadalafil side effects 

Tadalafil side effects are similar to those of sildenafil, though back pain and muscle aches are more commonly associated with tadalafil. Some side effects may improve as the body adjusts to the medication.

The most common side effects include:

• Headache

• Indigestion

• Back pain

• Muscle aches

• Nasal congestion

• Facial flushing

Similar to sildenafil, tadalafil should not be used with nitrates or guanylate cyclase stimulators. It also should not be used by anyone who has had a serious allergic reaction to tadalafil or any of its ingredients.

Rarely, PDE5 inhibitors such as sildenafil and tadalafil are linked to sudden vision loss or sudden hearing loss. Anyone who notices either symptom should stop taking the medication and get medical help right away.

Tadalafil or sildenafil: drug interactions 

Sildenafil and tadalafil can interact with certain medications, grapefruit, and alcohol. Some combinations can be dangerous, while others may change how well an ED medication works or raise the risk of side effects, according to the FDA-approved prescribing information for sildenafil and the prescribing information for tadalafil.

Major and dangerous interactions

Some medications should never be combined with sildenafil or tadalafil, while others require extra caution and guidance from a healthcare provider. These include:

• Nitrates: Taking either ED medication with nitrates, such as nitroglycerin or isosorbide, can cause a sudden, potentially life-threatening drop in blood pressure. This also applies to recreational drugs containing nitrites, like "poppers."

• Soluble guanylate cyclase (sGC) stimulators: Medications like riociguat (Adempas), used to treat certain types of pulmonary hypertension, also lower blood pressure. Combining them with sildenafil or tadalafil can cause blood pressure to fall dangerously low.

• Alpha-blockers: Medications such as tamsulosin (Flomax) and doxazosin (Cardura), often prescribed for enlarged prostate or high blood pressure, can amplify the blood pressure-lowering effects of ED medications. This may cause dizziness, fainting, or lightheadedness. A healthcare provider may start with a lower dose or advise against the combination.

Moderate and other interactions

Other substances can affect how sildenafil and tadalafil work in the body or increase the risk of side effects.

• Blood pressure medications: Combining ED medications with other medications used to treat high blood pressure, such as beta-blockers or calcium channel blockers, may lower blood pressure further. A healthcare provider can determine whether a combination is safe.

• CYP3A4 inhibitors and inducers: Certain medications affect an enzyme called CYP3A4, which helps the body break down sildenafil and tadalafil. Inhibitors, such as ketoconazole and ritonavir, can increase ED medication levels in the bloodstream, raising the risk of side effects. Inducers, such as rifampin, can lower those levels and potentially make treatment less effective. A healthcare provider may adjust the dose or limit how often an ED medication is taken when these medications are combined.

• Grapefruit and grapefruit juice: Grapefruit can interfere with CYP3A4, which may increase the amount of tadalafil, and possibly sildenafil, in the bloodstream. A healthcare provider can advise on whether grapefruit is safe to consume while taking either medication.

• Alcohol: Drinking large amounts of alcohol while taking sildenafil or tadalafil may increase the risk of dizziness, headaches, and low blood pressure. Limiting alcohol can help reduce these effects.

• Other PDE5 inhibitors: Taking sildenafil and tadalafil together, or combining either with another ED medication such as vardenafil (Levitra), may increase the risk of side effects, including low blood pressure. ED medications should not be combined unless a healthcare provider specifically instructs it.

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Sildenafil and tadalafil are commonly used to treat ED, among other conditions. They belong to the same class of medications and work by increasing blood flow to the penis.

• Sildenafil (Viagra) is taken as needed about 30 minutes to an hour before sexual activity and typically lasts 4–6 hours, which may suit planned sex.

• Tadalafil (Cialis) can last up to 36 hours, which may allow for more spontaneity. It can be taken as needed or at a lower dose for daily use.

• Both treat ED, and tadalafil can also help with BPH (enlarged prostate) symptoms when it is taken at a low-level daily dose.

• Tadalafil vs. sildenafil often comes down to personal preference and lifestyle: some people prefer sildenafil for its shorter window, while others choose tadalafil for its flexibility and longer effect. 

A healthcare provider can help determine which medication is the better fit.