Tadalafil: 7 things you should know
Medically reviewed by Carmen Fookes, BPharm. Last updated on Jun 10, 2020.
1. How it works
- Tadalafil is a medication used to treat erectile dysfunction (ED) or symptoms of benign prostatic hypertrophy (BPH).
- Tadalafil blocks 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.
- Tadalafil belongs to the class of medicines known as PDE-5 inhibitors.
- Tadalafil 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.
- Tadalafil is also used to treat the signs and symptoms of benign prostatic hyperplasia (BPH).
- Tadalafil is available as a lower strength tablet that can be taken on a daily basis, eliminating the need to 'plan' for sex.
- Tadalafil is also available as an 'as needed' tablet. The effect of one tablet lasts for up to 36 hours.
- Tadalafil is a generic, which means it is sold at a lower price compared to branded versions of tadalafil (such as Cialis).
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.
- 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, or a physical deformity of the penis (such as Peyronie's disease).
- May interact with some medications including nitrates - use of tadalafil 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.
- The dosage of tadalafil may need reducing in men with kidney disease. Once daily use may not be recommended in men with severe kidney disease.
- A lower dosage of tadalafil is recommended in men with mild-to-moderate liver disease. Tadalafil should be avoided with severe liver disease.
Notes: 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. For a complete list of all side effects, click here.
- Once daily Tadalafil can be taken without regard to sexual activity but should be taken at the same time every day (for example, on awakening).
- Tadalafil may be taken with or without food.
- Drinking alcohol after taking tadalafil may lower blood pressure and decrease sexual performance.
- Eating grapefruit or grapefruit products while taking tadalafil 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, or develop pain, numbness, tingling in your chest, arms, neck, or jaw.
- Do not take tadalafil if you are also taking a nitrate drug (such as nitroglycerin or isosorbide dinitrate/mononitrate) for chest pain or heart problems. Do not take tadalafil 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.
- Certain lifestyle and psychological factors, such as smoking, drinking, and stress, can impact on 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 tadalafil does not protect you from sexually transmitted diseases. Consider condom risk or abstinence if a sexual partner's history is unknown.
- Seek urgent medical advice if an allergic reaction, sudden vision loss or painful erections lasting more than four hours occur.
6. Response and Effectiveness
- Peak plasma concentrations of tadalafil are reached within 30 minutes to six hours (average time two hours) of a dose. Effects of 'as needed' tadalafil last for up to 36 hours.
- The recommended starting dose for once daily tadalafil for ED is 2.5mg; once daily tadalafil for BPH, 5mg; and 'as needed' tadalafil, 10mg. The dosage may be adjusted based on individual response.
Medicines that interact with tadalafil may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with tadalafil. 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 tadalafil 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, Cialis, sildenafil, vardenafil)
- 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)
- nitrates (eg, amyl nitrate, isosorbide dinitrate, isosorbide mononitrate, or nitroglycerin)
- others, such as aprepitant, cyclosporine, or imatinib.
In addition, taking tadalafil 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 tadalafil. 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 tadalafil. You should refer to the prescribing information for tadalafil for a complete list of interactions.
Tadalafil 03/2020. Drugs.com https://www.drugs.com/ppa/tadalafil.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use tadalafil only for the indication prescribed.
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