Combining sildenafil (Viagra) with tadalafil (Cialis) is not advised. Both drugs work in the same way as PDE5 inhibitors. Some studies have examined the use of these two together, but research indicates that combining them does not provide additional benefits. It also increases the risk of side effects.
Both sildenafil and tadalafil improve erections by boosting blood flow to the penis. They block an enzyme called PDE5, which breaks down a molecule called cGMP. cGMP helps relax blood vessels and muscles in the penis. By keeping cGMP active, these drugs make it easier to get and keep an erection when sexually stimulated.
A review in JAMA Network Open (2021) found that combining PDE5 inhibitors with other treatments gave only small improvements in erectile function. The benefits were modest. Moreover, combining the drugs may also increase side effects like headaches, dizziness, or low blood pressure. Using both drugs together is only sometimes considered for men who do not respond to one drug alone.
This article explores how both drugs work. It also covers their benefits, side effects, precautions, and safe combinations to improve erectile function, helping you make informed choices.
Contents
How Cialis and Viagra Work
Cialis (tadalafil) and Viagra (sildenafil) are PDE5 inhibitors. They are a type of medication used to treat erectile dysfunction (ED). They work by improving the body’s natural ability to get and keep an erection during sexual activity. When a man is sexually aroused, the body releases nitric oxide (NO) in the penis. This triggers an enzyme called guanylate cyclase. This enzyme increases a chemical messenger called cyclic guanosine monophosphate (cGMP). cGMP relaxes the walls of the penile blood vessels. This lets more blood enter the corpora cavernosa, leading to an erection.
Normally, another enzyme called PDE5 breaks down cGMP, which makes the erection go away. Cialis and Viagra block PDE5, keeping cGMP levels higher for longer. This helps maintain a firm erection. The main difference is how long they work. Viagra lasts 4 to 6 hours. Cialis can last up to 36 hours, allowing a longer time for sexual activity.
A study published in JAMA Internal Medicine (2002) reviewed 27 clinical trials and found that sildenafil (Viagra) greatly improved erectile function compared to a placebo. About 57% of men taking Viagra had successful intercourse, compared to only 21% in the placebo group. Most side effects were mild. They included flushing, headache, indigestion, and slight vision changes. No serious heart problems were reported.
In a study in Clinical Interventions in Aging (2006), tadalafil (Cialis) was shown to improve erections in men of all ages. They had different causes of ED. Cialis can work for up to 36 hours, allowing more flexibility and sexual spontaneity. Common side effects included headache, indigestion, back pain, nasal congestion, muscle aches, and flushing. The study found it effective and generally safe, but noted that long-term safety should be studied further, especially for older men or those with other health issues.
Let’s examine what happens when both drugs are taken together.
What Happens When You Combine Viagra and Cialis?
Both Viagra (sildenafil) and Cialis (tadalafil) belong to the class of drugs called PDE5 inhibitors. They work in a similar way to increase blood flow to the penis, but taking them together will not double the effect. Both medicines target the same enzyme, so combining them will not make erections stronger. It only increases the amount of PDE5 blocking already happening.
What does increase are the side effects. Using Viagra and Cialis together can cause too much widening of blood vessels. This can lead to low blood pressure, dizziness, fainting, headaches, flushing, or vision changes. In rare cases, it can cause serious heart problems, especially in men with heart disease or those taking nitrates.
As per a study in Andrologia (2015), researchers looked at two treatments for men with erectile dysfunction. One group took tadalafil 5 mg daily. The other group took tadalafil 5 mg daily plus sildenafil 50 mg when needed. The combination worked better, especially for men with more serious ED. It improved erection scores and sexual activity reports from both men and their partners. Both treatments had similar mild side effects, showing the combination was safe and more effective.
However, doctors usually advise not to take two PDE5 inhibitors at the same time. Medical guidelines recommend using only one drug at a time and at the lowest dose needed to avoid dangerous side effects.
Cialis may work for up to 36 hours, whereas Viagra usually lasts around 4 to 6 hours. If you take them on the same day, their effects can overlap. This increases the risk of side effects like low blood pressure or a prolonged erection (priapism).
Even if you take Viagra many hours after Cialis, tadalafil may still be active in your system. This means your body processes both drugs together, which can raise the risk of side effects, even if you do not feel the full effect of both at the same time.
Can I Take Low-Dose Cialis and Viagra Together?
Yes, you can but only if your doctor clears you for the combination therapy. In certain cases, a urologist may prescribe a combination of daily low-dose Cialis (2.5 mg or 5 mg) and occasional Viagra (25 mg or 50 mg) for patients with erectile dysfunction (ED) who have not responded adequately to monotherapy. This approach is typically considered when other treatments have been ineffective. It’s essential that this combination be used under strict medical supervision due to the increased risk of side effects such as low blood pressure, dizziness, and priapism.
Can I Take Cialis One Day and Viagra the Next?
Yes, it is generally safe to take Cialis on one day and Viagra on the next, provided there is a sufficient gap between doses. Cialis has a longer duration of effect, with a half-life of around 17.5 hours. Viagra has a shorter half-life of about 4 hours. To minimize the risk of overlapping effects, it’s advisable to wait at least 24 hours between taking these medications.
| Medication | Half-Life | Duration of Action | Safe Interval Before Next Dose |
| Cialis | 17.5 hours | 36 hours | 24-48 hours |
| Viagra | 4 hours | 4 to 6 hours | 24 hours |
Can I Take Cialis in the Morning and Viagra at Night?
No, taking Cialis in the morning and Viagra later the same day is generally unsafe, as Cialis remains active in the body for many hours. This combination may increase the likelihood of side effects like low blood pressure or unusually long-lasting erections. Consult a doctor to ensure that there is no hidden cause for your ED.
If your case is special, a doctor may allow combination therapy. It should only be done under strict medical supervision. Below are some key safety tips to note if you’re keen on combination therapy:
- 24+ hour gap rule: Avoid taking sildenafil too soon after tadalafil to reduce risk of blood pressure drop.
- Monitor BP: Keep an eye on your blood pressure especially if on antihypertensives or alpha-blockers.
- Adjust doses individually: Always take and adjust doses under physician supervision.
- Caution: Never combine PDE5 inhibitors with nitrates.
What Happens if You Take Viagra While on Cialis?
Taking Viagra while Cialis is still active in your system can be risky. Both drugs are PDE5 inhibitors, so using them together can increase the chance of side effects like low blood pressure, dizziness, fainting, or prolonged erections (priapism). In rare cases, serious heart problems may occur. Some doctors may prescribe a daily low-dose Cialis for ongoing erectile support and allow occasional Viagra under strict supervision, but this is only for men who do not respond to one drug alone.
To reduce risk, it’s important to wait at least 24 hours between taking a full dose of Cialis and a dose of Viagra. This is because of their different half-lives: Cialis lasts about 17.5 hours, while Viagra lasts about 4 hours. Waiting helps prevent the drugs from overlapping too much in the bloodstream, which can cause a dangerous drop in blood pressure.
Even with proper spacing, taking both on the same day is still risky. Drug overlap can amplify side effects like dizziness, fainting, and priapism. A study in JAMA Open Network (2021) highlights that combination therapies for erectile dysfunction, such as PDE5 inhibitors paired with other treatments like shockwave therapy or vacuum devices, can modestly improve erectile function. Reported side effects were generally mild, including headache, flushing, indigestion, nasal congestion, and muscle aches. However, combining PDE5 inhibitors like Cialis and Viagra may increase the risk of serious issues such as low blood pressure, prolonged erections, and cardiovascular complications, so medical supervision is essential.
Let’s take a closer look at the ways Viagra and Cialis might be used together, and what you need to know about safety, timing, and potential effects.
How Can You Take Cialis and Viagra Together?
Normally, taking Cialis (tadalafil) and Viagra (sildenafil) together is not recommended because combining them increases the risk of side effects like low blood pressure, dizziness, and prolonged erections.
However, in certain cases, a urologist may consider combining the two under strict medical supervision. A urologist may combine Cialis and Viagra in rare cases. This usually happens when a single drug does not work well. For example, men with long-term diabetes, nerve damage, or after prostate surgery may have treatment-resistant ED. Some men have ED caused by multiple health issues, and one drug alone is not enough. Others may use daily low-dose Cialis but need extra support for special occasions.
Combination may also be considered alongside therapies like shockwave treatment or testosterone replacement. In some cases, smaller doses of both drugs are safer than a higher dose of one, especially for men with heart or blood pressure concerns. All combination therapy is closely monitored by a doctor.
Compounded dosing is also an approach where a pharmacy customizes the strength of each drug to lower the risk of side effects. Compounding pharmacies carefully follow regulations to ensure medicines are safe and the doses are correct.
In these cases, doctors usually recommend:
- Waiting at least 24 hours (preferably 48 hours if you take Cialis first) between full doses of Cialis and Viagra to reduce overlap and side effects.
- Considering a daily low-dose Cialis (for baseline erectile support) and using Viagra occasionally for additional effect, but only under medical supervision.
Even with these strategies, close monitoring is required. Blood pressure, heart health, and other medications must be reviewed before attempting any combination therapy.
How Long To Wait Between Cialis and Viagra?
Cialis (tadalafil) and Viagra (sildenafil) should not be taken at the same time. Both drugs are PDE5 inhibitors, and combining them increases the risk of serious side effects, especially low blood pressure, dizziness, and fainting.
Recommended waiting time between Cialis and Viagra:
- Viagra after Cialis: Cialis stays active for up to 36 hours. Doctors generally recommend waiting at least 2 days (48 hours) after taking Cialis before using Viagra. This ensures most of the tadalafil has left your system.
- Cialis after Viagra: Viagra usually lasts 4 to 6 hours. Most doctors suggest waiting at least 24 hours after taking Viagra before using Cialis.
Even after these intervals, individual factors like age, kidney or liver health, and other medications can affect how long the drugs stay in your system. Always talk to your doctor before switching or combining these medications.
What Are the Side Effects of Taking Cialis and Viagra Together?
Taking Cialis (tadalafil) and Viagra (sildenafil) together increases the risk of side effects because both drugs work in the same way to widen blood vessels. When combined, their effects on blood pressure, circulation, and vision can add up.
Common side effects (more likely when combined):
- Headache
- Flushing (warmth/redness in face or neck)
- Nasal congestion or runny nose
- Indigestion
- Dizziness
- Back pain or muscle aches
- Visual changes (blurred vision, color tint, light sensitivity)
Severe side effects (rare but more dangerous when combined):
- Severe drop in blood pressure (hypotension)
- Fainting or collapse
- Chest pain
- Stroke-like symptoms (sudden weakness, slurred speech)
- Sudden loss of vision – Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION)
- Sudden loss of hearing
- Prolonged, painful erection lasting more than 4 hours (priapism)
| Side Effect | Severity | Likelihood when combined |
| Headache | Mild to Moderate | High |
| Flushing | Mild | High |
| Nasal Congestion | Mild | Moderate |
| Indigestion | Mild | High |
| Dizziness | Mild to Moderate | High |
| Visual Changes | Moderate to Severe | Moderate |
| Back Pain / Muscle Aches | Mild | Moderate |
| Hypotension | Severe | Moderate |
| Fainting | Severe | Moderate |
| Chest Pain / Stroke-like Symptoms | Severe | Low to Moderate |
| Sudden Vision Loss (NAION) | Severe | Rare |
| Sudden Hearing Loss | Severe | Rare |
| Priapism | Severe | Moderate to Rare |
Let’s explore how Cialis’s effectiveness can be boosted, including safe methods and possible supportive treatments to maximize results.
What Can I Take To Enhance Cialis?
Cialis (tadalafil) is effective for many who suffer from erectile dysfunction (ED). However, in certain situations, combining it with other treatments such as supplements, medicines, or therapies can lead to better outcomes. Research suggests that when tadalafil is used alongside other targeted treatments, it can result in improved results, especially for men who also have other health conditions.
A study published in the Journal of Clinical Medicine (2024) evaluated a supplement named Icarifil in men with mild to moderate ED. Participants were given Icarifil alone, tadalafil alone, or both together. Icarifil is made up of ingredients like L-carnitine, L-citrulline, Panax ginseng, and other natural components. The group that took both Icarifil and tadalafil showed the greatest improvement in erection scores and sexual activity. They also reported higher satisfaction with their results. Only minor side effects were noted.
For men with low levels of vitamin D, combining it with tadalafil seems to offer better results than tadalafil alone. A study in Urologia Internationalis (2021) examined men with ED and low vitamin D. One group took tadalafil 5 mg daily. The other took tadalafil plus 4,000 IU of vitamin D daily. Both groups experienced improvements, but the combination group showed greater gains in erection quality and sexual desire.
Natural supplements like L-arginine and carnitine may also support tadalafil’s effectiveness. A study in Sexual Medicine (2020) found that men with ED who took either L-arginine (2,500 mg daily), tadalafil (5 mg daily), or both showed improvement over 12 weeks. All three groups improved, but the combination group had the most significant improvements, especially among those with mild to moderate ED. Side effects were mild, and no participants discontinued treatment.
Low-intensity shockwave therapy (LiST) may enhance the effects of tadalafil and provide better erections. A study in The Journal of Sexual Medicine (2022) involved 50 men with mild to mild-moderate ED. Half of them received LiST for three weeks, while the other half also took tadalafil 5 mg daily for four weeks. The combination group experienced better and longer-lasting erections compared to the placebo group. No side effects were reported.
Some prescription drug combinations also work well with tadalafil. Tamsulosin, a medication used for urinary issues, can be taken with tadalafil to improve both erections and urine flow in men with an enlarged prostate (BPH). A study in the Journal of Clinical Medicine (2019) tested tadalafil 5 mg daily, both with or without tamsulosin 0.4 mg. Both groups improved, but the combination was more effective for urinary symptoms. Side effects were slightly more common with the combination.
Finasteride, another drug used for prostate conditions, can also be used with tadalafil. In the U.S., this combination is marketed as Entadfi. A review in Therapeutics and Clinical Risk Management (2015) found that using finasteride along with daily tadalafil improved urinary symptoms more quickly and effectively than using finasteride alone. It also helped maintain or enhance erections, while finasteride alone can sometimes lead to a decrease in sexual function. Side effects were mild and comparable to those experienced with tadalafil alone.
Here’s a table summary of substances that can enhance the effect of cialis to get a quick overview.
| Combination | Benefit |
| Icarifil + Tadalafil (L-citrulline, L-carnitine, Panax ginseng, etc.) | It showed the biggest improvement in erection scores and sexual activity. |
| Vitamin D + Tadalafil | It gives better erections and higher sexual desire in men with low vitamin D |
| L-Arginine + Tadalafil | It provides greater improvement in mild to moderate ED than either alone. |
| Low-Intensity Shockwave Therapy (LiST) + Tadalafil | It gives better and longer-lasting erections. |
| Tamsulosin + Tadalafil | The combination improves erections and urine flow in men with enlarged prostate (BPH). |
| Finasteride + Tadalafil (Entadfi) | It provides faster relief of urinary symptoms and preserved erectile function. |
Is Combining ED Meds More Effective?
No, combining them usually isn’t more effective. It may be considered only if a doctor finds standard treatment insufficient.
A study in JAMA Network Open (2021) looked at multiple studies to see if using more than one treatment for ED works better than just one. One of the studies looked at taking Cialis and Viagra together. The study suggests that the effect of combination therapies for ED tends to plateau, meaning that adding more treatments does not always lead to much greater improvement. Most men saw only small gains in erectile function, and after a certain point, combining additional therapies didn’t significantly increase the benefit. This is why the overall improvement was modest, even with multiple treatments.
Additionally, because it can cause side effects like low blood pressure or heart problems, doctors don’t usually recommend using them at the same time.
Viagra VS Cialis: Which Is Better?
Viagra and Cialis are both effective treatments for erectile dysfunction, but they work in slightly different ways that make one more suitable than the other depending on a man’s needs. Viagra, which contains sildenafil, usually works within 30 to 60 minutes and lasts for about 4 to 6 hours, making it a good option for planned sexual activity. Cialis, which contains tadalafil, can take about 30 minutes to start working but lasts up to 36 hours, earning it the nickname “the weekend pill.” The main difference between Cialis and Viagra is their duration of action, with Cialis offering more flexibility and less need for timing, while Viagra provides reliable short-term support. Some men prefer Cialis for spontaneity, while others choose Viagra for its quick and predictable effect. The better option depends on personal preference, medical history, and a doctor’s advice.
What Is The Strongest Erectile Dysfunction Pill?
The strongest ED pill is sildenafil, known as Viagra, which improves erections in up to 84% of men. It works within 30 minutes, lasts about 4 hours, and increases blood flow, but should not be combined with nitrates.
How Long Does Tadalafil Last?
Tadalafil last up to 36 hours in the body. Its long duration of action allows men more flexibility and spontaneity in sexual activity compared to other erectile dysfunction medicines that wear off sooner. It is also known as “the weekend pill.”
How Long Does Sildenafil Last?
Sildenafil lasts about 4 hours on average, though effects may be strongest in the first 2 hours. It usually begins working within 30 to 60 minutes. The duration of action varies between individuals, but on average, sildenafil last long enough to support planned sexual activity effectively.
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