Tadalafil

Medication Overview

Tadalafil (Cialis) is an oral medication used to treat male erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). Its primary mechanism of action is the inhibition of phosphodiesterase-5 (PDE5), which relaxes blood vessels and promotes blood flow, thereby improving erectile function or alleviating symptoms of pulmonary hypertension.

This drug has a relatively long half-life, with effects lasting up to 36 hours after a single dose, earning it the nickname "weekend pill". Clinically, it is not only used for sexual dysfunction but also as a long-term treatment option for pulmonary arterial hypertension.

Brand Names and Generic Name

Brand names include Cialis (for ED treatment) and Adcirca (for PAH), with the generic name being Tadalafil. Different brands may vary in dosage or formulation, and usage should follow a physician's prescription.

Drug Classification

It belongs to the class of phosphodiesterase-5 (PDE5) inhibitors and also has vasodilatory properties. These drugs primarily act on smooth muscle, increasing cyclic GMP levels in specific tissues to relax blood vessels.

Indications

The main indications include:

• Male erectile dysfunction (ED): requires sexual stimulation to be effective.
• Pulmonary arterial hypertension (PAH): used to improve exercise capacity and cardiopulmonary function.

Additionally, some countries have approved its use for benign prostatic hyperplasia (BPH), but this indication may not yet be approved in Taiwan. Usage should be clarified with a pharmacist or physician.

Common Side Effects

Mild side effects include:

• Headache (occurs in approximately 10-15% of patients)
• Back pain
• Nasal congestion or rhinorrhea
• Gastrointestinal discomfort

Serious side effects require immediate medical attention:

• Sudden hearing loss accompanied by tinnitus
• Blurred vision or visual disturbances (possibly non-arteritic anterior ischemic optic neuropathy, NAION)
• Prolonged erection lasting more than 4 hours (priapism)

If any of the above symptoms occur, discontinue the medication immediately and seek medical attention.

Warnings and Precautions

Contraindicated in:

• Patients using any dose of nitrates (such as Nitroglycerin) for angina
• Individuals allergic to Tadalafil or excipients
• Patients with severe hepatic or renal impairment requiring dose adjustment

Pregnancy and breastfeeding safety are classified as Category C. Use during late pregnancy may harm the fetus, and women of childbearing age should take contraceptive precautions. Alcohol consumption should be avoided during treatment, as it may exacerbate hypotension side effects.

Drug Interactions

Contraindicated interactions:

• Use with nitrates (such as Isosorbide) can cause dangerous hypotension
• Use with alpha-blockers (such as Tamsulosin) requires caution, as it may lead to significant blood pressure drops

Other considerations:

• Use with antihistamines or antidepressants may prolong drug effects
• Avoid concurrent use with large amounts of grapefruit juice, which may increase blood concentration

Dosage and Administration

For ED: Starting dose is usually 5-10 mg taken 30 minutes before sexual activity on an empty stomach, with a maximum of once daily. For PAH: Starting dose is 40 mg once daily, with dose adjustments made gradually under medical supervision.

Swallow the tablet whole; do not chew. Taking with high-fat meals may delay absorption but does not significantly affect total absorption. Follow the physician's instructions strictly; do not adjust the dose on your own.

Missed Dose Management

If a dose for ED is missed and it is not close to the next scheduled dose, take it as soon as possible; if it is near the next dose time, skip the missed dose and resume the regular schedule. Do not double the dose.

For PAH patients, if a daily dose is missed, take it immediately and adjust the next dose time to prevent symptom deterioration.

Overdose Management

Overdose may cause severe hypotension, visual disturbances, or prolonged erections. Seek immediate medical attention, inform healthcare providers of the drug name and dose, and hospitalization or antidote administration may be necessary.

If symptoms of shock (such as dizziness, cold sweat, weak pulse) occur, call emergency services immediately and seek urgent medical care.

 

Frequently Asked Questions

Do I need to follow a specific diet when taking Tadalafil?

It is recommended to avoid high-fat meals when using Tadalafil, as fatty foods may prolong the drug's effect. It is generally advised to take it on an empty stomach or after a meal, but avoid consuming large amounts of fatty foods simultaneously to ensure stable efficacy. If you have concerns about timing, consult your doctor or pharmacist.

How can I alleviate facial flushing or headaches caused by Tadalafil?

Facial flushing and headaches are common side effects, usually transient. Reducing the initial dose, avoiding alcohol or hot sources (such as hot showers) can help alleviate symptoms. If symptoms are severe or persistent, discontinue the medication and contact healthcare providers for assessment and possible dose adjustment.

What interactions should I be aware of when combining Tadalafil with other cardiac medications?

Tadalafil has serious interactions with nitrates (such as nitroglycerin), which can cause dangerously low blood pressure. Use with cardiovascular drugs should be disclosed to your doctor, including antihypertensives or other heart medications, to avoid risks.

With a long-lasting effect of up to 36 hours, how can I prevent it from affecting daily activities?

The long-acting nature of Tadalafil may increase the risk of spontaneous erections. Follow the prescribed fixed dose and avoid increasing frequency on your own. If an erection persists longer than 4 hours, seek immediate medical attention, as this is a medical emergency.

Does long-term use lead to dependency on the medication for erectile function?

There is currently no evidence that Tadalafil causes physiological dependence. It only helps improve blood flow and does not weaken natural erectile ability. Regular follow-up to evaluate the underlying cause and lifestyle adjustments are recommended to maintain long-term treatment effectiveness.