Cialis (tadalafil): what the evidence says — educational information, not a medical diagnosis or personal prescription

Quick summary

• Cialis is a brand name for tadalafil, a prescription medicine used mainly for erectile dysfunction (ED), and also for benign prostatic hyperplasia (BPH).
• It belongs to a class called PDE5 inhibitors and works by improving blood flow in response to sexual stimulation.
• It can work for up to 36 hours, which is longer than some similar drugs.
• Common side effects include headache, flushing, nasal congestion, and indigestion; serious side effects are rare but possible.
• It must not be used with nitrates (for chest pain) due to risk of dangerous low blood pressure.

What is known

1. What Cialis is and how it works

Tadalafil (Cialis) is approved in many countries for:

• Erectile dysfunction (ED)
• Benign prostatic hyperplasia (BPH)
• Both ED and BPH together
• In a different dosage form/brand, pulmonary arterial hypertension (PAH)

It works by blocking the enzyme phosphodiesterase type 5 (PDE5). This increases levels of cyclic GMP, which relaxes smooth muscle and improves blood flow. In ED, this helps blood flow to the penis during sexual stimulation. It does not cause an automatic erection; sexual arousal is still required.

2. Effectiveness for erectile dysfunction

Large randomized controlled trials show that tadalafil significantly improves erectile function compared with placebo. Benefits include:

• Improved ability to achieve and maintain an erection
• Improved scores on validated questionnaires (such as IIEF)
• Effectiveness across different causes of ED (diabetes, post-prostate surgery, psychological factors), though response rates vary

One distinctive feature is its longer duration of action (up to 36 hours). This allows more flexibility in timing compared with shorter-acting PDE5 inhibitors.

Major urology guidelines (e.g., European Association of Urology, American Urological Association) list PDE5 inhibitors, including tadalafil, as first-line therapy for ED in most men without contraindications.

3. Effectiveness for BPH (enlarged prostate)

Tadalafil is also approved for lower urinary tract symptoms due to BPH. Studies show modest but clinically meaningful improvements in urinary symptoms such as:

• Urinary frequency
• Urgency
• Weak stream

It does not significantly reduce prostate size but may relax smooth muscle in the prostate and bladder.

4. Safety profile

In clinical trials and post-marketing data, tadalafil is generally well tolerated. Common side effects include:

• Headache
• Facial flushing
• Back pain or muscle aches
• Indigestion (dyspepsia)
• Nasal congestion

Rare but serious risks include:

• Sudden vision or hearing loss
• Priapism (erection lasting more than 4 hours)
• Severe drop in blood pressure (especially with nitrates)

Men with significant cardiovascular disease should be evaluated before starting treatment for ED, as sexual activity itself carries cardiac demand.

5. Drug interactions and contraindications

Do not use tadalafil with:

• Nitrates (e.g., nitroglycerin, isosorbide)
• Guanylate cyclase stimulators (e.g., riociguat)

Caution is needed with:

• Alpha-blockers
• Strong CYP3A4 inhibitors (e.g., some antifungals, certain antibiotics)
• Severe liver or kidney disease

For official prescribing details and approved dosage information, refer to the U.S. FDA label:
FDA-approved prescribing information for tadalafil (Cialis) or the European Medicines Agency product information.

What is unclear / where evidence is limited

• Long-term outcomes beyond several years: While safety data are reassuring, very long-term comparative data are limited.
• Use in complex cardiovascular disease: Evidence supports cautious use in stable patients, but high-risk cardiac populations are often excluded from trials.
• Combination therapy strategies: For example, tadalafil combined with testosterone or other ED treatments — evidence exists but is not uniform.
• Psychological vs. organic ED: PDE5 inhibitors help many men with mixed causes, but outcomes vary, and psychological therapy may be necessary.

As with many medications, real-world effectiveness may differ slightly from controlled clinical trial settings.

Overview of approaches

Management of erectile dysfunction or BPH usually includes several components:

Lifestyle and risk factor modification

• Smoking cessation
• Weight management
• Regular physical activity
• Blood pressure, cholesterol, and diabetes control

These steps may improve erectile function and overall cardiovascular health.

Oral medications (PDE5 inhibitors)

Cialis (tadalafil) is one option among several PDE5 inhibitors. Choice may depend on:

• Duration of action preference
• Side-effect profile
• Cost and availability
• Coexisting conditions (e.g., BPH)

Typical dosing regimens are described in official prescribing information from regulatory authorities (see FDA link above). This article does not provide personal dosing instructions.

Other treatments for ED

• Vacuum erection devices
• Penile injections
• Hormonal therapy (in confirmed testosterone deficiency)
• Penile implants (surgical option)
• Psychosexual therapy

For broader context on men’s health topics, see our evidence-based guide to erectile dysfunction and overview of men’s cardiovascular risk factors. If you are researching medications in general, our section on how to read drug safety information may help.

Evidence summary table

Statement	Confidence level	Why
Tadalafil improves erectile function compared with placebo.	High	Multiple randomized controlled trials and guideline endorsements.
Tadalafil works up to 36 hours in many men.	High	Pharmacokinetic data and clinical trials consistently show prolonged duration.
Tadalafil improves urinary symptoms in BPH.	High	Supported by RCTs and regulatory approval for this indication.
Tadalafil is safe for all men with heart disease.	Low	Patients with high-risk cardiac disease often excluded from trials; individual assessment required.
Combining tadalafil with lifestyle changes enhances outcomes.	Medium	Lifestyle changes improve vascular health, but direct additive effects vary between studies.

Practical recommendations

When to see a doctor

• Erectile problems lasting more than a few weeks
• ED with chest pain, shortness of breath, or known heart disease
• Sudden onset of ED (may signal vascular or neurological issues)
• Urinary symptoms affecting quality of life

Before your appointment

• List current medications (including supplements).
• Note chronic conditions (diabetes, hypertension, heart disease).
• Be ready to describe when symptoms started and how often they occur.
• Report any history of vision/hearing problems or prolonged erections.

General safety tips

• Do not combine tadalafil with nitrates.
• Avoid buying prescription medicines from unverified online sources.
• Seek urgent care for chest pain after taking tadalafil or for an erection lasting more than 4 hours.

If you are comparing options, our overview of treatment approaches for benign prostatic hyperplasia may also be useful.

Sources

• U.S. Food and Drug Administration (FDA). Prescribing Information for Cialis (tadalafil).
• European Medicines Agency (EMA). Tadalafil product information.
• American Urological Association (AUA). Guideline on Erectile Dysfunction.
• European Association of Urology (EAU). Guidelines on Sexual and Reproductive Health.
• National Health Service (NHS). Tadalafil: medicine overview.