Erectile dysfunction (ED) is a common and often complex condition that primarily affects men over the age of 40. However, data from the 2021 National Survey of Sexual Wellbeing showed that 17.9% of men in the US aged 18-24 also showed signs of ED. Experts estimate that by 2025, over 322 million men around the world will be living with ED.
Fortunately, there are several treatment options available. These include oral medications, hormone therapy, vacuum devices, injections, and even counseling. Among these, oral drugs remain the most widely used.
In this article, we’ll examine generic sildenafil vs. Cialis vs. Viagra, and compare how they work, how they’ve performed in clinical studies, and which one may be the right choice based on your needs, timing, and treatment goals.
| 🔑 Key Takeaways ➤ Clinical trials confirm that generic and brand-name Viagra perform similarly, with nearly identical drug levels in the bloodstream and no significant differences in side effects. ➤ Cialis may offer added psychological and relationship benefits, such as higher confidence and satisfaction during sex, compared to sildenafil or Viagra. ➤ All three medications begin working within a similar timeframe, around 15 to 30 minutes, with many men reporting successful intercourse within that window. ➤ Cialis lasts significantly longer than Viagra or sildenafil, staying effective for up to 36 hours. ➤ Patient preference studies consistently show a higher preference for Cialis, mainly due to its longer duration and flexibility for timing sexual activity. ➤ Common side effects are shared across all three drugs, including headaches and flushing, though Cialis may be more associated with back pain and Viagra with facial redness. ➤ FDA-approved uses vary slightly. Viagra and sildenafil are only approved for ED, while Cialis is also approved to treat BPH, making it useful for men with both conditions. ➤ Generic versions offer the most affordable options, but brand-name Cialis may be cheaper in low daily doses. |
Effectiveness of Generic Sildenafil, Cialis, and Viagra
Generic sildenafil works just as well as Viagra. Both medications contain the same active ingredient, sildenafil citrate, in identical doses. Since the FDA requires that generics match brand-name drugs in how they’re absorbed and act in the body, they’re held to the same standard for effectiveness.
In a 2015 clinical trial, researchers compared a 50 mg dose of generic sildenafil with the same dose of Viagra to determine whether both versions were processed similarly in the body.
The results showed nearly identical drug levels in the bloodstream. The slight variations fell well within the acceptable range defined by the FDA and European health authorities. Participants tolerated both forms well, with no major side effects reported.
When comparing Viagra and its generic to Cialis, studies have shown that Cialis may offer added benefits.
A meta-analysis comparing Cialis and Viagra found both drugs to be equally effective in improving erectile function and sexual satisfaction, based on International Index of Erectile Function (IIEF) scores. However, Cialis came out ahead in a few specific areas:
- It significantly boosted confidence during sexual activity (based on SEAR Confidence scores).
- It showed greater improvement in sexual relationships (SEAR Sexual Relationship scores).
- It had higher overall satisfaction ratings (based on EDITS scores).
Another study evaluated men who were new to ED treatments, comparing 20 mg Cialis with 100 mg Viagra. Both drugs improved erectile strength, penetration success, and overall sexual performance.
Which Works Faster?
Generic sildenafil, Viagra, and Cialis all begin working within a similar timeframe. Some men experienced results from sildenafil/Viagra in as little as 12 minutes, with most seeing effectiveness by 30 minutes. One study found that about 51% of men had successful intercourse within 20 minutes, with an average onset time of 36 minutes.
Cialis also acts quickly. In a stopwatch-based study, the 20 mg dose showed a significant effect as early as 15 minutes, while the 10 mg dose began showing results around 26 minutes. Moreover, 52% of men on 20 mg Cialis reported a successful sexual experience within 30 minutes, compared to 35.1% on placebo.
Which Acts Longer?
Cialis, often referred to as “the weekend pill,” is well known for its long-lasting effects, staying active for up to 36 hours. Sildenafil (including Viagra) generally lasts for about 4 hours, but recent studies suggest the effects can continue far longer in some men.
A study found that Viagra could remain effective for up to 12 hours, with the ability to support erections during that time. However, the duration of each erection tends to decrease over time:
- 1 hour after taking: Erections can last 26-33 minutes, as the drug is at peak concentration.
- 8 hours after: Duration drops to 11-23 minutes.
- 12 hours after: Effects become weaker, with erections lasting around 8-16 minutes.
These findings are supported by a European trial, where 97% of men achieved successful intercourse within an hour of taking Viagra, and 74% were still able to do so after 12 hours.
Which Is More Preferred?
In a study that compared the effects of 50 mg Viagra and 20 mg Cialis, more men chose Cialis as their preferred treatment. Out of 190 participants who completed the trial, 66.3% selected Cialis, while 33.7% chose Viagra. The results were consistent across different age groups, regardless of how long the participants had been dealing with ED or whether they had used Viagra before.
Another trial showed similar results. Cialis was preferred by 69.1% of men, compared to 30.9% who opted for Viagra. Those who favored Cialis often said they appreciated the longer duration, which allowed for sexual activity hours after taking the pill.
A newer study also supported these findings. Patients who had tried both medications tended to favor Cialis overall. This trend was more noticeable among younger men with fewer health issues and those experiencing ED for the first time.
| ✂️ In Short Studies show that generic sildenafil and Viagra are equally effective. Cialis may offer added psychological and relationship benefits, such as increased sexual confidence and overall satisfaction. Preference studies also show that a majority of men who tried both drugs chose Cialis over Viagra, often because of its longer-lasting effects and greater flexibility. In terms of onset, all three begin working within a similar window, with some men experiencing effects in as little as 12 to 15 minutes, and around half of the participants reporting successful intercourse within 30 minutes. When it comes to duration, Cialis lasts much longer, up to 36 hours, compared to sildenafil and Viagra, which typically remain active for about 4 hours, though newer data suggests it may still support erections up to 12 hours in some users. |
Mechanism of Action of Sildenafil, Cialis, and Viagra
Cialis (tadalafil) and Viagra (sildenafil) are in a group of medications called PDE5 inhibitors. These drugs block an enzyme known as phosphodiesterase type 5 (PDE5). This enzyme normally breaks down cGMP, a chemical that helps relax the muscles in blood vessel walls.
When PDE5 is blocked, cGMP stays in the body longer.
As cGMP levels rise, it triggers a chain reaction inside smooth muscle cells that relaxes them. This happens by lowering calcium levels, pushing potassium out of the cell, and stopping a protein that usually causes muscle tightening. The end result is relaxed blood vessels and increased blood flow. In the penis, this relaxation allows blood to fill the erectile tissue, leading to an erection.
Note that these medications do not cause an erection by themselves. Sexual arousal is still needed for them to work. They only support the body’s natural response when a person is sexually stimulated.
Sildenafil vs. Cialis vs. Viagra’s Side Effects
Cialis, Viagra, and sildenafil share many of the same side effects because they all belong to the same class of drugs. These include:
- Headache
- Stomach discomfort
- Back pain
- Myalgia (muscle pain or muscle soreness)
- Stuffy nose
- Flushing or redness of the skin
- Pain in limb
- Changes in eyesight
- Nausea
- Dizziness
- Rash
A head-to-head comparison showed that Cialis tends to cause back and muscle aches more frequently, whereas Viagra/sildenafil is more commonly linked to facial flushing.
In addition, both medications can occasionally lead to serious side effects, including:
- Priapism – an erection that lasts longer than six hours and is painful. If not treated quickly, it may result in lasting damage to the penis.
- Sudden Vision Loss – a rare complication that may signal NAION (non-arteritic anterior ischemic optic neuropathy), which can lead to permanent or partial vision loss.
- Hearing Loss – unexpected hearing problems, often with symptoms like ringing in the ears or dizziness.
- Allergic Reactions – in some cases, individuals may experience severe symptoms such as hives, facial or throat swelling, breathing difficulty, or extreme dizziness.
These serious reactions are rare, but if they happen, it’s essential to stop using the medication immediately and get medical attention.
FDA-Approved Indications of Sildenafil, Cialis, and Viagra
The FDA first approved Viagra in March 1998 for the treatment of erectile dysfunction (ED) in adult men. Generic sildenafil became available in the US after Viagra’s patent expired in December 2017.
Like Viagra, generic sildenafil is approved for erectile dysfunction, but it is also approved under a different brand name, Revatio, for the treatment of pulmonary arterial hypertension (PAH). While the sildenafil citrate is chemically identical, the approved use and dosing are not interchangeable:
- Revatio (generic) is not approved by the FDA for treating ED.
- Viagra (generic) is not approved for treating PAH.
Cialis received FDA approval in November 2003 for erectile dysfunction. Unlike Viagra and sildenafil, Cialis is also approved to treat benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate that can cause urinary symptoms.
The FDA approved Cialis for BPH in October 2011. It is the only PDE5 inhibitor approved for the treatment of both ED and BPH and for men who have both conditions simultaneously.
Dosage and Administration of Sildenafil, Cialis, and Viagra
Cialis and Viagra are each taken once per day, but Cialis offers more flexible dosing choices. See how they compare below:
| Feature | Cialis | Viagra/Sildenafil |
| Dosage forms and strengths | Oral tablets (2.5 mg, 5 mg, 10 mg, 20 mg) | Oral tablets (25 mg, 50 mg, 100 mg) |
| Starting dose for ED | 10 mg as needed before sex or 2.5 mg daily | 50 mg as needed before sex |
| Dose adjustments | Can go up to 20 mg or down to 5 mg when taken as needed. May increase to 5 mg if taken for daily use in ED treatment. | Can be increased to 100 mg or lowered to 25 mg |
| Maximum dose | 20 mg (as needed) or 5 mg (daily use) | 100 mg |
| When to take it | Taken 30 minutes before sexual activity for as-needed use or taken at the same time each day for daily use. | Taken 30 minutes before sexual activity |
Price Comparison of Generic Sildenafil vs. Cialis vs. Viagra
Among the three, low-dose Cialis is often priced the lowest overall. However, when comparing similar dosages, generic sildenafil usually offers the best value. Keep in mind that actual costs can vary based on the pharmacy, location, and whether you have insurance or use discount programs.
Below is a breakdown of the average prices based on data from GoodRx.
| Formulation | Dose | Average Retail Price (30 tablets) |
| Viagra | 25 mg | $3,195.56 |
| 50 mg | $2,974.28 | |
| 100 mg | $3,022.70 | |
| Sildenafil (generic Viagra) | 25 mg | $900.90 |
| 50 mg | $891.35 | |
| 100 mg | $1,010.15 | |
| Cialis | 2.5 mg | $446 |
| 5 mg | $457 | |
| 10 mg | $2,444 | |
| 20 mg | $2,486 | |
| Tadalafil (generic Cialis) | 2.5 mg | $285 |
| 5 mg | $287 | |
| 10 mg | $1,244 | |
| 20 mg | $1,239 |
Wrap-up
Generic sildenafil works just as well as Viagra. Cialis is also effective but has added benefits, lasts up to 36 hours, and is often preferred by men. All three medications start working within 15 to 30 minutes, and their side effects are mostly the same.
Generic sildenafil usually costs the least when comparing equal doses. Branded versions are significantly more expensive.
If you’re looking for a cheaper, reliable option, generic sildenafil is a good choice. If you prefer longer effects and more freedom in timing, Cialis may be a better fit.
Frequently Asked Questions
Is Cialis 20 mg equal to Viagra 100 mg?
Not exactly. While both doses are considered the highest strengths for each drug, they aren’t directly equivalent. The effectiveness also varies by individual. In one study, both drugs showed similar improvements in erectile function and sexual performance, but participants preferred 20 mg Cialis over 100 mg Viagra.
Is it safe to combine Viagra and Cialis?
No, using both medications together is not recommended. They work in similar ways and combining them increases the risk of side effects like low blood pressure, dizziness, and priapism.
Is it okay to take Viagra or Cialis if you don’t have erectile dysfunction?
It’s not advised. Taking these medications without ED doesn’t improve sexual performance and can lead to side effects like headaches, blood pressure drops, and dependency on the drug for arousal. These medications should only be used under medical supervision and for approved conditions.
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