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Cialis Vs. Viagra: Drug Comparison

Compare common side effects, interactions, warnings, and more.

Medical Review byMike Bohl, MD, MBA, MPH, MS, ALMNov 4, 2024

Medication Name

Summary

Prescription only

Cialis® (tadalafil) is used to treat erectile dysfunction (ED) and the symptoms of benign prostatic hyperplasia (BPH). It works by relaxing the muscles of blood vessels and increasing blood flow to particular areas of the body, notably the penis. Cialis is known for its long-lasting effects, allowing for more spontaneity, as it can remain effective for up to 36 hours. It is typically taken as needed, but a lower daily dose option is also available for continuous treatment. Common side effects of Cialis include headaches, indigestion, back pain, and muscle aches, which typically resolve within a few days. It is important to use Cialis with caution, especially for individuals with cardiovascular conditions, and to avoid combining it with nitrates or certain other medications due to the risk of serious interactions.

Prescription only

Viagra® (sildenafil citrate), a phosphodiesterase type 5 (PDE5) inhibitor, is an oral medication used to treat erectile dysfunction (ED). It is taken only as needed, usually about an hour before sexual activity, though it can be effective if taken between 30 minutes to 4 hours prior. It is very important not to take Viagra more than once a day, as exceeding this frequency increases the risk of serious side effects, including vision loss and significant drops in blood pressure.

Drug Category

Phosphodiesterase-5 (PDE5) inhibitor

Phosphodiesterase-5 (PDE5) inhibitor

Approved Uses

Cialis (tadalafil) is indicated to treat:

  • Erectile dysfunction (ED)

  • The signs and symptoms of benign prostatic hyperplasia (BPH)

  • ED and the signs and symptoms of BPH (ED/BPH)

Viagra (sildenafil citrate) is indicated to treat:

  • Erectile dysfunction (ED)

Dosage

  • Typically taken orally as needed prior to sexual activity, up to once daily (5 mg, 10 mg, and 20 mg doses) OR taken orally once daily (2.5 mg and 5 mg doses)

  • Comes in 2.5 mg, 5 mg, 10 mg, and 20 mg tablets

  • Typically taken orally as needed approximately 60 minutes before sexual activity, up to once daily

  • Comes in 25 mg, 50 mg, and 100 mg tablets

Known Common Side Effects

Most common adverse reactions (≥2%) include:

  • Headache

  • Indigestion

  • Back pain

  • Muscle pain

  • Nasal congestion

  • Flushing

  • Pain in limb

Most common adverse reactions (≥2%) include:

  • Headache

  • Flushing

  • Indigestion

  • Abnormal vision

  • Nasal congestion

  • Back pain

  • Muscle pain

  • Nausea

  • Dizziness

  • Rash

Interactions & Contraindications

  • Administration of Cialis to patients using any form of organic nitrate is contraindicated

  • History of known serious hypersensitivity reaction to Cialis or Adcirca

  • Drug interactions: Nitrates, alpha blockers, antihypertensives, alcohol, CYP3A4 inhibitors (e.g., ketoconazole, ritonavir), CYP3A4 inducers (e.g., rifampin)

  • Administration of Viagra to patients using nitric oxide donors, such as organic nitrates or organic nitrites in any form

  • Known hypersensitivity to sildenafil or any component of tablet

  • Drug interactions: Nitrates, alpha blockers, antihypertensives, CYP3A4 inhibitors (e.g., ritonavir, ketoconazole, itraconazole, saquinavir, erythromycin)

Warnings & Precautions

  • Patients should not use Cialis if sex is inadvisable due to cardiovascular status

  • Use of Cialis with alpha blockers, antihypertensives or substantial amounts of alcohol (≥5 units) may lead to low blood pressure

  • Cialis is not recommended in combination with alpha blockers for the treatment of BPH, because efficacy of the combination has not been adequately studied and because of the risk of blood pressure lowering

  • If taking potent inhibitors of CYP3A4, dose should be adjusted

  • Patients should seek emergency treatment if an erection lasts >4 hours

  • Patients should stop Cialis and seek medical care if a sudden loss of vision occurs in one or both eyes, which could be a sign of non arteritic ischemic optic neuropathy (NAION)

  • Patients should stop Cialis and seek prompt medical attention in the event of sudden decrease or loss of hearing

  • Prior to initiating treatment with Cialis for BPH, consideration should be given to other urological conditions that may cause similar symptoms

  • Patients should not use Viagra if sexual activity is inadvisable due to cardiovascular status

  • Patients should seek emergency treatment if an erection lasts >4 hours

  • Patients should stop Viagra and seek medical care if a sudden loss of vision occurs in one or both eyes, which could be a sign of non arteritic anterior ischemic optic neuropathy (NAION)

  • Patients should stop Viagra and seek prompt medical attention in the event of sudden decrease or loss of hearing

  • Caution is advised when Viagra is co-administered with alpha-blockers or anti-hypertensives

  • Decreased blood pressure, fainting, and prolonged erection may occur at higher sildenafil exposures

References

*This information is from the label for brand name Cialis®. See the Full Prescribing Information for more complete information. Tadalafil, the active ingredient in Cialis, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient tadalafil.

*This information is from the label for brand name Viagra®. See the Full Prescribing Information for more complete information. Sildenafil, the active ingredient in Viagra, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient sildenafil.