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Tadalafil - Indications, Mechanism of Action, Dosage, and Side Effects

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Tadalafil is a drug commonly used to treat male erectile dysfunction, prostate problems, and urinary difficulties. Read this article to learn more.

Medically reviewed by

Dr. J. N. Naidu

Published At September 22, 2022
Reviewed AtFebruary 2, 2023

What Is Tadalafil?

Tadalafil is commonly sold under the brand name Cialis. It addresses male problems related to penile erection, prostate enlargement, and urologic diseases. Tadalafil also works as a muscle relaxant because it relaxes the muscles of the blood vessels. As a result, the blood supply of the penis and other body parts increases, allowing males to get and keep their erection firm.

Tadalafil is also sold under a brand called Adcirca, which is used in treating pulmonary arterial hypertension (high blood pressure that affects the lungs and right side of the heart). This drug also accelerates the exercise capacity of females. In addition to erectile dysfunction, Tadalafil also works against benign prostate hyperplasia. It is a condition in which the prostate gland becomes enlarged and causes urologic problems.

What Are the Indications of Tadalafil?

Tadalafil belongs to the class of medications known as phosphodiesterase inhibitors. It is an enzyme whose primary area of focus is the penis. The indications of Tadalafil are listed below:

  • Erectile Dysfunction -Erectile dysfunction or impotence is when the penis fails to harden or becomes erect when the person is sexually stimulated. Normally, when the person is mentally or sexually stimulated, the body commands the blood vessels to increase the blood flow to the penis. However, in patients with erectile dysfunction, this mechanism fails to occur. As a result, they cannot keep the penis erect during sexual intercourse.

  • Benign Prostate Hyperplasia -The prostate gland is located close to the neck of the urinary bladder. Benign prostate hyperplasia or non-cancerous enlargement of the prostate gland causes serious problems related to urination. The patient might have reduced urine output, urinary frequency, urgency, difficulty starting the urine stream, and nocturia (frequently urinating at night). Tadalafil works to reduce the intensity and severity of these symptoms. It also reduces the chance of prostate surgery.

  • Pulmonary Venous Hypertension - Pulmonary venous hypertension is a condition that affects females and reduces their exercise abilities. The condition is known as pulmonary venous hypertension, when blood flows under high pressure in the artery that supplies blood to the lungs. Due to this condition, the blood vessels in the lungs become resistant to blood flow, and the right ventricles must work hard to pump the blood. Tadalafil relaxes the blood vessels of the lungs, increases the blood flow to the lungs, and reduces the heart workload.

What Is the Mechanism of Action of Tadalafil?

Tadalafil or Cialis is a selective phosphodiesterase-5 (PDE-5) inhibitor that produces several therapeutic effects, the most common being smooth muscle relaxation. Several causes of erectile dysfunction include psychogenic, neurogenic, iatrogenic, vasculogenic, and endocrine. These factors cause dysfunction of the penile smooth muscle relaxation by directly acting on the smooth muscles or inhibiting the neuronal signaling pathway. When a person is sexually stimulated, the penile blood flow increases because of the relaxation of the penile arteries and muscles. When this happens, certain chemicals are released from the nerve endings that stimulate the relaxation of the smooth muscles of the penis. PDE-5 enzymes disrupt this neuronal signaling pathway and the substances that cause an erection. This is the time when Tadalafil comes into action. It inhibits the PDE-5 enzymes, causes sexual stimulation, and maintains sexual function.

Effect of Tadalafil on Pulmonary Venous Hypertension:

The blood pressure is raised in pulmonary venous hypertension due to several internal factors. Usually, the body maintains an equilibrium between the factors that promote the narrowing and widening of the blood vessels. However, venous hypertension or high blood pressure occurs when the factors responsible for vasodilation (widening of the veins) outnumber the ones accountable for vasoconstriction (narrowing of the veins). When the blood pressure increases, the afterload on the heart increases because it has to work hard to pump blood to the lungs. Tadalafil comes into action and exerts its therapeutic effect to relax the heart muscles and widens the blood vessels.

Effect of Tadalafil on Benign Prostate Hyperplasia:

Benign prostate hyperplasia causes urinary dysfunction because the cells of the prostate gland increase excessively and block the urine flow from the bladder. When the urine does not flow outside the body, it remains in the kidneys and the urinary bladder. As a result, the risk of kidney diseases increases. In such situations, Tadalafil does not induce smooth muscle relaxation; instead, it activates the pathways to inhibit the proliferation of prostate cells.

Dosage of Tadalafil:

The dosage of Tadalafil varies from patient to patient. Follow the instructions on the drug label or consult the doctor before taking the drug. Information related to the average dose of this drug has been described below:

Composition of Tadalifil -

Active Ingredients: Tadalafil.

Inactive Ingredients: Croscarmellose sodium, hypromellose, iron oxide, hydroxypropyl cellulose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, sodium lauryl sulfate, talc, titanium dioxide, and triacetin.

Oral Dosage Form (Tablet) -

For the Management of Benign Prostate Hyperplasia (Daily Use):

  • Adults - A single dose of 5 mg is to be taken once daily. Take the drug at the same time each day and do not take it twice.

  • Children - No information is available about the dose.

For the Management of Erectile Dysfunction (As Needed):

  • Adults - A dose of 10 mg is to be taken once daily, 30 minutes before the sexual activity. The doctor might adjust the dose as per the patient’s requirement.

  • Children - No information is available about the dose.

For the Management of Erectile Dysfunction (Daily Use):

  • Adults - A single dose of 2.5 mg is to be taken once daily regardless of the timing of sexual activity. The doctor might adjust the dose as per the patient’s requirement.

  • Children - No information is available about the dose.

For the Management of Erectile Dysfunction and Benign Prostate Hyperplasia (Daily Use):

  • Adults - A single dose of 5 mg is to be taken once daily regardless of the timing of sexual activity. The doctor might adjust the dose as per the patient’s requirement.

  • Children - No information is available about the dose.

For the Management of Pulmonary Arterial Hypertension:

  • Adults - 40 mg. It means two 20 mg tablets to be taken once daily at the same time each day. Do not divide it into two doses.

  • Children - The dose will be determined by the doctor.

What Should the Patient Inform the Doctor Before Taking Tadalafil?

Tadalafil is not meant for every patient. After looking at the patient’s condition, the doctor can judge whether he is suitable for the drug or not. Before taking Tadalafil, the patient must inform the doctor if he is suffering from the following conditions:

  • Curved penis or defect present in the penis congenitally.

  • Leukemia (cancer of the blood-forming tissues).

  • Multiple myeloma (cancer of the white blood cells).

  • Sickle cell anemia.

  • Males above 50 years.

  • Coronary artery diseases.

  • Hypertension.

  • Diabetes.

  • Hyperlipidemia (large amounts of lipids or fats in the blood).

  • Crowded disc (eye disease).

  • Angina (chest pain).

  • The habit of smoking.

  • Irregular heartbeat or arrhythmia.

  • History of a heart attack in the last three months.

  • History of heart failure in the previous six months.

  • Hypotension (low blood pressure).

  • Retinal problems.

  • Retinitis pigmentosa (hereditary eye disease).

  • Liver and kidney disease.

  • Stomach ulcers.

  • Bleeding disorders.

  • Erection that lasted more than four hours.

  • Pulmonary venous occlusive disease (a type of pulmonary or lung disease).

How Should the Drug Tadalafil Be Used?

Tadalafil is a tablet and must be taken orally with or without food. If the patient takes the drug for erectile dysfunction, he must follow the doctor’s instructions and guidelines. There are two different methods by which the drug can be taken. It can be taken either daily or when the need arises. However, the patient must consult the doctor about the drug schedule. Sometimes, the drug might be taken half an hour before the sexual activity, but take only one tablet in a day and not more than that. The doctor will help decide the best time the drug should be taken before sexual activity. The patient can continue his sexual activity even between the doses. The patient must ensure that he takes the tablet simultaneously each day. However, patients having medical conditions and taking medications for the same might be prescribed a lower dose of the drug. Follow the instructions provided on the prescription label and take medicine exactly as directed. The patient can ask the doctor if he cannot understand the prescription label.

What Are the Side Effects of Tadalafil?

The side effects of Tadalafil can be divided into rare, common, and less common ones. The less commonly seen side effects of Tadalafil are listed below:

  • Pain in the back, arms, and lower jaw.

  • Blurred vision, chills, cold sweats, and mental confusion.

  • Heaviness and tightness in the chest.

  • Fainting, dizziness, and lightheadedness after getting up from a lying or sitting position.

  • Irregular heartbeat.

  • Hearing loss.

  • Increased erection.

  • Nausea, nervousness, and weakness.

  • Bloody nose.

  • Burning, crawling, numbness, and tingling sensations.

  • Dry or itchy eyes.

  • Congestion.

  • Difficulty in swallowing and moving.

  • Dryness of mouth and sore throat.

  • Stuffed or runny nose.

  • Fever, diarrhea, and drowsiness.

  • Reduced tactile sensitivity.

  • Swollen joints and eyelids.

More Common Side Effects of Tadalafil:

  • Belching.

  • Indigestion.

  • Heartburn.

  • Stomach pain and discomfort.

Rare Side Effects of Tadalafil:

  1. Scaly skin.

  2. Delayed speech.

  3. Changes in color vision.

  4. Prolonged or painful penile erection.

Drug Interactions -

Drug interactions occur when two different medicines are administered together. If the patient takes some other drugs along with Tadalfil, the doctor might change the dose or recommend other precautions. The patient must inform the doctor if he is taking any of the following medications:

  • Amyl nitrite.

  • Isosorbide dinitrate and Isosorbide mononitrate.

  • Boceprevir.

  • Erythrityl Tetranitrate.

  • Nitroglycerin.

  • Pentaerythritol Tetranitrate.

  • Clarithromycin.

  • Cobicistat.

  • Nefazodone.

  • Bunazosin.

  • Alfuzosin.

  • Atazanavir.

  • Propatyl Nitrate.

  • Riociguat.

  • Ketoconazole.

  • Nefazodone.

  • Posaconazole.

  • Phenoxybenzamine

  • Tamsulosin.

  • Voriconazole.

  • Urapidil.


Tadalafil is widely used to manage problems related to male erection and prostate gland. The drug is a boon for those suffering from depression and anxiety due to impaired sexual life. Doctors and patients prefer this drug because it reduces the risk of surgery and saves them from surgical trauma. However, several side effects are associated with this drug, and the patient needs to inform the doctor about the over-the-counter and other drug supplements he is taking before using this drug. Though this drug is readily available in the market, it should be taken only after getting a prescription from the doctor. Consult a doctor to know more about the benefits and side effects of Tadalafil.

Dr. J. N. Naidu
Dr. J. N. Naidu

General Practitioner


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