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Cialis side effects and how to avoid them

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By | Updated on Aug. 29, 2023 Medically reviewed by Karen Berger, Pharm.D.
Prescription pad with pill bottle: Cialis side effects, warning and interactions

Key takeaways

  • Cialis (tadalafil) treats erectile dysfunction and benign prostatic hyperplasia by relaxing muscles and arteries in the penis to maintain an erection. It requires sexual stimulation to work.

  • Common Cialis side effects include headache, stomach upset, back pain, muscle pain, and nasal congestion. Severe side effects may consist of prolonged erections, sudden loss of vision or hearing, and cardiovascular events.

  • Cialis may lower blood pressure, posing risks for those with cardiovascular conditions. It has several contraindications and interactions, including nitrates, guanylate cyclase stimulators, and other medications.

  • To minimize side effects, take Cialis under a healthcare provider’s care and ensure it’s purchased from a licensed pharmacist. Take it as directed, avoid grapefruit, limit alcohol intake, and do not use Cialis recreationally.

Cialis side effects | Blood pressure | How long do side effects last? | Warnings | Interactions | How to avoid side effects

Cialis (tadalafil) is a brand-name prescription medication that treats erectile dysfunction, or the signs and symptoms of an enlarged prostate (benign prostatic hyperplasia or BPH). Classified as a phosphodiesterase type 5 (PDE5) inhibitor, tadalafil relaxes smooth muscles and arteries in the penis. 

Cialis also allows more blood to flow to the penis for a longer period to maintain an erection. Cialis also requires sexual stimulation in order to work for erectile dysfunction. 

Cialis helps to relieve the lower urinary tract symptoms of benign prostatic hyperplasia. It is thought to work for BPH by relaxing muscles in the lower urinary tract. 

As can be expected, medicines that affect blood vessels may have unwanted side effects and potentially risky drug interactions. People considering Cialis should be familiar with these side effects, potential interactions, and any medical conditions that may render the medicine unsuitable. 

RELATED: Learn more about Cialis | Get Cialis discounts

Common side effects of Cialis

The most common side effects of Cialis are:

  • Headache
  • Stomach upset/diarrhea
  • Back pain
  • Muscle pain
  • Nasal congestion
  • Upper respiratory infection
  • Flushing
  • Pain in the limbs or extremities
  • Swelling of the nose and pharynx
  • Dizziness

Serious side effects of Cialis

Cialis can cause serious side effects such as:

    • Prolonged erections: Though rare, some people have reported prolonged erections (erections lasting longer than four hours) or priapism (painful erections lasting longer than six hours) when taking drugs similar to Cialis. Both prolonged erections and priapism should receive emergency medical treatment. Priapism may damage erectile tissues if it is not treated right away.
    • Sudden loss of vision: Non-arteritic anterior ischemic optic neuropathy or NAION has been reported—rarely—in people taking drugs like tadalafil. NAION can cause a sudden decrease or complete loss of vision in one or both eyes. Immediately stop the drug and get emergency medical help if you notice changes in vision.
    • Sudden loss of or decrease in hearing: Hearing loss has been reported with Cialis and may be accompanied by dizziness or ringing in the ears. Immediately stop the drug and get emergency medical help if you notice hearing loss.
    • Cardiovascular events such as fainting, chest pain, heart attack, or stroke: Most (but not all) people who have had severe cardiovascular events while taking Cialis had pre-existing risk factors.
    • Low blood pressure (hypotension): Tadalafil lowers blood pressure, so low blood pressure is a possible side effect.
    • Severe allergic reactions: Rare but severe (and potentially lethal) hypersensitivity reactions due to Cialis include hives, Stevens-Johnson syndrome, and exfoliative dermatitis.

Blood pressure

Cialis relaxes the smooth muscles in arteries, lowering blood pressure slightly. Because of this, low blood pressure, or hypotension, might be a problem. Hypotension is defined as blood pressure that dips below 90/60 millimeters of mercury (mmHg). At its mildest, low blood pressure makes people vulnerable to fainting, falls, and injuries. If blood pressure falls too low, vital organs may fail which could result in death.

In tadalafil’s phase III clinical trials, no patients (out of 949) experienced clinical hypotension. In phase III studies evaluating the safety of tadalafil when taken with drugs that lower blood pressure (called antihypertensives), the combination only slightly increased the risk of low blood pressure. When taken with two or more antihypertensives, tadalafil did not increase the incidence of hypotension.

Another form of low blood pressure is orthostatic hypotension, which is characterized by a sudden decline in blood pressure that happens when a person stands up from a sitting or lying position. While often harmless, producing little more than lightheadedness, orthostatic hypotension can result in serious consequences depending on its cause. In the study (mentioned above) that focused on this issue, tadalafil was found to have no clinically relevant effects on orthostatic hypotension..

How long do Cialis side effects last?

Most common side effects of Cialis are temporary and will abate within a few hours or days after discontinuing the medicine. Some, like headache, back pain, and muscle pain, were the main reasons a small number of people in the initial clinical trials stopped using Cialis. 

Other side effects, such as severe allergic reactions, prolonged erections, priapism, hearing loss, and cardiovascular events, require immediate medical attention and may require long-term attention. Severe but rare possible adverse events such as damage to erectile tissues due to priapism, hearing loss, heart attack, or stroke may have lifelong consequences. Vision loss due to NAION can be permanent.

Cialis contraindications & warnings

Cialis may not be the right drug for all men, particularly because of its effects on the cardiovascular system. Cialis is contraindicated for men:

  • With known serious hypersensitivity to tadalafil
  • With severe kidney disease (renal impairment) or men on dialysis
  • With severe liver disease (hepatic impairment)
  • Who take nitrates or guanylate cyclase stimulators

Some people can take Cialis but may have medical conditions that require caution, that is, careful monitoring and a possible dose reduction. These include:

  • Mild to moderate kidney disease
  • Mild to moderate liver disease
  • High blood pressure
  • Certain cardiovascular problems
  • Diabetes
  • High cholesterol (hyperlipidemia)
  • A history of non-arteritic anterior ischemic neuropathy (NAION) or risk factors such as optic disk crowding
  • Penile deformities such as Peyronie’s disease, cavernosal fibrosis, or angulation
  • Any condition that carries a risk of priapism such as sickle cell anemia, leukemia, or multiple myeloma

According to DailyMed, patients with cardiovascular conditions such as myocardial infarction, angina, hypotension, stroke or uncontrolled arrhythmias at present, or the recent past, should not take Cialis because no clinical studies have been conducted to evaluate safety and efficacy.

Abuse and dependency

The recreational use of Cialis and other erectile dysfunction medications (EDMs) is surprisingly high, particularly among sexually active young men. Besides the risk of side effects, men misusing EDM drugs are more likely to make lifestyle choices that put them at a greater risk for sexually transmitted diseases and potential drug interactions with other illicit or recreational drugs such as “poppers.”

There is some uncertainty that medications like tadalafil cause physical dependency, tolerance, or withdrawal. The consensus view is that they don’t. It’s particularly difficult to separate EDM dependency from associated lifestyle choices. Many men abusing EDMs also use recreational drugs that can cause erectile dysfunction, making chronic use of EDMs necessary. Highly active sexual lifestyles may also necessitate chronic or high-dose use of EDMs.

Drugs like Cialis that do not cause physical dependence or withdrawal can still result in abuse and behavioral dependence. Mental health professionals diagnose this condition as “substance abuse disorder,” which can be mild to severe depending on how much the misuse of a drug impairs relationships and functioning. In some cases, the recreational use or misuse of tadalafil can certainly justify a diagnosis of substance abuse disorder. Successfully ending the misuse may require therapy.

Children

Cialis is never to be given to people younger than the age of 18.

Pregnancy and breastfeeding

Cialis is not approved for use in women.

Senior citizens

The manufacturer does not recommend dosage adjustment based on age alone. However, the full picture of age and other conditions should be taken into account when deciding on the appropriate dosage of Cialis.

Cialis interactions

Cialis can be taken with or without food. However, that does not mean that Cialis can be taken with all foods. Grapefruit has substances that slow down the body’s metabolism of tadalafil. It takes longer for the body to break down the drug, so the concentration of tadalafil in the blood increases, making side effects more likely.

Men taking tadalafil should also limit alcohol intake. Like Cialis, alcohol lowers blood pressure. Combining too much alcohol with Cialis could cause severely low blood pressure. The FDA recommends no more than four drinks per day when taking Cialis, but check with your healthcare provider regarding a safe amount of alcohol consumption based on your other conditions and/or medications you take.

Cialis has several drug interactions men should know when taking the medication.

  • Nitrates—CONTRAINDICATED: Nitrates are medications used to treat chest pain (angina). They act in a way very similar to Cialis. They increase the levels of a molecule (cyclic guanosine monophosphate) that causes artery muscles to relax. Arteries rapidly widen, allowing blood flow to increase to the heart. Nitrates include nitroglycerin, nitroprusside, isosorbide mononitrate, and isosorbide dinitrate. Combining nitrates with Cialis risks reducing blood pressure so drastically that it results in a heart attack or stroke. If nitrates are ever required, they cannot be used until 48 hours after the last dose of Cialis.
  • Guanylate cyclase (GC) stimulators–CONTRAINDICATED: Cialis is never given to people taking the GC stimulators Adempas (riociguat) or Verquvo (vericiguat). Adempas treats pulmonary arterial hypertension (high blood pressure in the arteries that go from the heart to the lungs). Verquvo is used in certain patients with chronic heart failure. GC stimulators work in much the same way as Cialis and nitrates by increasing the chemical that widens arteries. The combination risks causing severely low blood pressure.
  • Nitrites: Nitrites are similar to nitrates. They relax smooth muscles in the arteries, so combining them with tadalafil increases the risk of low blood pressure. Nitrites can be found in some recreational drugs known as  “poppers,” including amyl nitrite or butyl nitrite.
  • Erectile dysfunction medications (EDMs): Hypotension and other side effects are at greater risk if Cialis is used with other erectile dysfunction medications that, like Cialis, are PDE5 inhibitors. These drugs, which include Viagra (sildenafil) and Levitra (vardenafil), should be avoided when taking Cialis.
  • Blood pressure medications (antihypertensives): Combining Cialis with medications that lower blood pressure carries a small risk of low blood pressure, so therapies may require monitoring blood pressure. Doses may sometimes need to be changed. Other drugs, such as opioids, antidepressants, and antipsychotic medications may also lower blood pressure, so blood pressure monitoring may be required when they’re combined with Cialis.
  • Alpha-blockers: Alpha-blockers are used to treat high blood pressure or an enlarged prostate. Because of the risk of low blood pressure, combining Cialis with these drugs is generally not recommended.
  • CYP3A4 inhibitors: Besides grapefruit, several drugs also slow down the metabolism of tadalafil by blocking an enzyme, called CYP3A4, which breaks down tadalafil. These drugs include some types of antibiotics, some types of HIV medications, some types of antifungals (ketoconazole and itraconazole), some types of benzodiazepines, and some types of corticosteroids. Combining tadalafil with a strong CYP3A4 inhibitor may cause serious side effects. A lower dose of Cialis may be required.
  • CYP3A4 inducers: Alternatively, some drugs speed up the body’s metabolism of tadalafil, reducing the benefit of a Cialis dose. Called CYP3A4 inducers, these drugs do not cause serious problems. Examples of CYP3A4 inducers include rifampin, phenobarbital, phenytoin, and carbamazepine. At worst, the Cialis dose might need to be increased. Healthcare providers and pharmacists are well-versed in these drugs, so they can easily spot the combination and offer advice.

How to avoid Cialis side effects

The risk of Cialis side effects can be minimized by following a few general pointers:

1. Take Cialis under the care of a healthcare provider

Do not take Cialis or other erectile dysfunction medications without a prescription from a licensed healthcare provider. To avoid potentially hazardous side effects, the prescribing healthcare provider should perform an in-person physical examination and medical history review. For people with certain conditions, regular medical visits may be required to ward off serious side effects.

2. Only purchase Cialis from a licensed pharmacist

Purchasing Cialis or other erectile dysfunction medications through alternative channels carries the risk of purchasing counterfeit or unsafe medications. Dose strengths may be wrong, raising the risk of ineffectiveness or side effects. Purchase Cialis by prescription only, and through a licensed pharmacy, such as your local pharmacy or your insurance’s mail order facility.

3. Take Cialis as directed

Take the dose as prescribed. Read, understand, and follow the medication guide or patient instructions that come with the medicine. A pharmacist, doctor, or other healthcare provider can answer any questions or clear up any confusion. Above all, do not increase or decrease the dose without consulting your healthcare provider. If effectiveness or side effects are a problem, talk to your healthcare provider about adjusting the dose.

4. Tell the doctor about all medical conditions and medications

Because of the risk of side effects, always make sure the prescribing healthcare provider knows about:

  • Any medical conditions, particularly 
    • Heart or circulation problems
    • Stroke
    • Blood pressure problems
    • Blood cell problems (such as sickle cell anemia)
    • Bleeding problems
    • Kidney problems
    • Liver problems
    • Eye problems (such as retinitis pigmentosa or severe vision loss)
    • Stomach ulcers
    • Deformed penis shape or
    • A history of prolonged (> 4 hours) erections
    • Any medical condition that may make sexual activity potentially hazardous
  • History of alcohol abuse 
  • All medications, over-the-counter medications, supplements, and remedies being taken

5. Do not take more than one dose of Cialis per day

Tadalafil, the active ingredient in Cialis, stays in the body for a long time. When taking Cialis as needed, a single dose (taken at least 30 minutes before sexual activity) will allow for sexual activity for up to 36 hours. When taking Cialis as a daily dose, take the dose at approximately the same time every day.

6. Avoid grapefruit

Cialis can be taken with or without food. The one exception is grapefruit, which has substances that interfere with the body’s ability to eliminate tadalafil from the body. To lower the risk of side effects, avoid eating grapefruit or drinking grapefruit juice when taking Cialis.

7. Do not drink too much alcohol

Cialis lowers blood pressure. So does alcohol. A moderate amount of alcohol is okay, but the FDA has set a safety limit of four drinks when taking Cialis. By that, they mean four 5-ounce glasses of wine or four shots of the stronger stuff. Consult your healthcare provider on safe alcohol intake, though, because you may have other conditions or take other medications that could interact with alcohol.

8. Use protection against sexually transmitted diseases

Cialis does not protect against sexually transmitted diseases. Use appropriate protection such as condoms and spermicide. Consult your healthcare provider for medical guidance.

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