Cialis: 7 things you should know

Medically reviewed by Carmen Pope, BPharm. Last updated on Nov 20, 2023.

1. How it works

• Cialis is a brand (trade) name for tadalafil which may be used to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH).
• Cialis (tadalafil) works by blocking the action of an enzyme known as cGMP-specific phosphodiesterase type-5 (PDE-5). This enzyme breaks down cGMP, a substance that induces smooth muscles to relax. Blocking PDE-5 means increased levels of cGMP within the smooth muscles which promotes muscle relaxation and vasodilation (a widening of blood vessels).
• High levels of PDE-5 are found in the penis, lungs, and retina. PDE-5 is also found throughout the body within the smooth muscle cells of blood vessels and muscles.
• Cialis (tadalafil) belongs to the class of medicines known as PDE-5 inhibitors.

2. Upsides

• Cialis is used for the treatment of erectile dysfunction (ED). It increases blood flow to the penis following sexual stimulation and allows men to keep an erection hard enough for sex.
• Cialis is also used to treat the signs and symptoms of benign prostatic hyperplasia (BPH).
• Cialis is available as a lower-strength tablet that can be taken daily basis, eliminating the need to 'plan' for sex.
• Cialis is also available as an 'as needed' tablet. The effect of one tablet lasts for up to 36 hours.
• The recommended 'as needed' dose for Cialis is 10mg, taken before anticipated sexual activity. The dose may be increased to 20mg or decreased to 5mg. It should not be taken more than once a day.
• The recommended starting dose for Cialis intended for once-daily use is 2.5mg, taken at the same time each day, without regard to the timing of sexual activity. This may be increased to 5mg/day based on need and tolerability.
• May be taken with or without food.
• Cialis is available as a generic, under the name tadalafil.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• A headache, dyspepsia, back pain, nasal congestion, and flushing are the most commonly reported side effects.
• Other side effects include a drop in blood pressure, muscle or limb pain, or conjunctivitis.
• Rarely, may decrease blood flow to the optic nerve causing sudden vision loss. The risk is greater in people aged older than 50, with diabetes, heart disease, high blood pressure, high cholesterol, who smoke, or with certain pre-existing eye problems.
• The dosage of Cialis may need to be reduced in men with kidney disease. For men with CLCR of 30 to 50 mL/min, a starting dose of 5mg not more than once per day is recommended. The maximum dose is 10mg not more than once every 48 hours.
• For men with CLCR of < 30 mL/min or on hemodialysis, the maximum dose is 5mg not more than once every 72 hours. Once-daily use may not be recommended in men with CLCR < 30 mL/min.
• For men with mild-to-moderate liver disease (Child-Pugh Class A or B), the dose should not exceed 10mg once per day. Cialis is not recommended in severe liver disease (Child-Pugh Class C).
• Rarely, may cause other side effects including hearing loss, or lead to painful erections lasting longer than four to six hours. See your doctor immediately if this happens.
• May not be suitable for some people including those with angina, chest pain, or other heart conditions, liver or kidney problems, blood or bleeding disorders, stomach ulcers, certain eye conditions, a physical deformity of the penis (such as Peyronie's disease), or serious prior hypersensitivity reactions to tadalafil.
• May interact with some medications including nitrates - the use of Cialis and nitrates is contraindicated because of the severe hypotension that can develop. May also interact with other medications including ketoconazole or ritonavir; dosage adjustment is recommended.
• A lower dosage of Cialis is recommended in men with mild-to-moderate liver disease. Cialis should be avoided with severe liver disease.
• Not for use in females.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

• Cialis is used to treat erectile dysfunction (ED) and to reduce symptoms of benign prostatic hyperplasia (BPH). One 'as needed' tablet lasts for 36 hours or Cialis is available as a lower dosage that can be taken daily, eliminating the need to 'plan for sex'.

5. Tips

• Once daily Cialis can be taken without regard to sexual activity but should be taken at the same time every day (for example, on awakening).
• Cialis may be taken with or without food.
• Do not split Cialis tablets, swallow them whole.
• Drinking alcohol after taking Cialis may lower blood pressure and decrease sexual performance.
• Eating grapefruit or grapefruit products while taking Cialis is not recommended.
• Always talk to your doctor before taking ANY medication for ED. Some ED medications are not suitable for men with certain medical conditions.
• Call your doctor immediately if you experience dizziness or feel nauseous during sexual activity, angina pain, or develop pain, numbness, or tingling in your chest, arms, neck, or jaw.
• Do not take Cialis if you are also taking a nitrate drug (such as nitroglycerin or isosorbide dinitrate/mononitrate) for chest pain or heart problems. Do not take Cialis with recreational drugs such as 'poppers'. Taking these substances together can cause a sudden and dangerous drop in blood pressure.
• Always buy your ED medications from a reputable supplier as there are a lot of counterfeit products in circulation.
• Sexual activity can place stress on the heart and use of Cialis is not advisable for men for whom sexual activity is inadvisable as a result of their underlying cardiovascular status. If you experience any heart-related symptoms on initiation of sexual activity should not pursue further sexual activity until you have talked to your doctor.
• Certain lifestyle and psychological factors, such as smoking, drinking, and stress, can impact ED. Eliminating these - for example, staying more active, losing weight if you are overweight, reducing alcohol intake, stopping smoking, and reducing stress - may also help improve ED.
• Taking Cialis does not protect you from sexually transmitted diseases. Consider condom risk or abstinence if a sexual partner's history is unknown.
• Stop taking Cialis and seek urgent medical advice if an allergic reaction, sudden vision loss in one or both eyes, or painful erections lasting more than four hours occur.
• Cialis is not intended for women.

6. Response and effectiveness

• Peak plasma concentrations of Cialis are reached within 30 minutes to six hours (average time two hours) of a dose. Effects of 'as needed' Cialis last for up to 36 hours.
• The recommended starting dose for once-daily Cialis for ED is 2.5mg; once daily Cialis for BPH, 5mg; and 'as needed' Cialis, 10mg. The dosage may be adjusted based on an individual's response.

7. Interactions

Medicines that interact with Cialis may either decrease its effect, affect how long it works, or have less of an effect when taken with Cialis. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Cialis include:

• alpha-agonists (eg, clonidine, methyldopa)
• alpha-blockers (eg, alfuzosin, doxazosin, tamsulosin, or terazosin)
• antibiotics, such as clarithromycin, erythromycin, metronidazole, norfloxacin, rifabutin, rifampin, or tetracycline
• antidepressants, such as desipramine or sertraline
• antifungal medications, such as itraconazole, ketoconazole, or voriconazole
• cystic fibrosis medications, such as ivacaftor
• epilepsy medications, such as carbamazepine, oxcarbazepine, phenobarbital, phenytoin, or primidone
• erectile dysfunction medications (eg, alprostadil, sildenafil, vardenafil)
• GC stimulators, such as riociguat
• heart medications, such as amlodipine, amiodarone, atenolol, candesartan, captopril, clonidine, diltiazem, enalapril, irbesartan, losartan, nifedipine, propranolol, sotalol, or verapamil
• hepatitis medications, such as boceprevir and simeprevir
• HIV medications (eg, atazanavir, delavirdine, efavirenz, indinavir, etravirine, ritonavir, nevirapine, saquinavir, or tipranavir)
• medications that are potent inhibitors of CYP3A4 such as ketoconazole or ritonavir
• nitrates such as amyl nitrate, isosorbide dinitrate, isosorbide mononitrate, or nitroglycerin: contraindicated
• others, such as aprepitant, cyclosporine, or imatinib.

In addition, taking Cialis with too much alcohol can lead to orthostatic hypotension, which is a drop in blood pressure when you go from a sitting or lying down position to standing. Symptoms include a headache, dizziness, or fainting when standing. Antacids, such as magnesium hydroxide or aluminum hydroxide may also affect the absorption of Cialis. Grapefruit juice may also increase the side effects of tadalafil.

Note that this list is not all-inclusive and includes only common medications that may interact with Cialis. You should refer to the prescribing information for Cialis for a complete list of interactions.

References

• Cialis (tadalafil) [Package Insert]. Revised 07/2023. Eli Lilly and Company. https://www.drugs.com/pro/cialis.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Cialis only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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