Atazanavir with Tadalafil Interaction Details

Brand Names Associated with Atazanavir

  • Atazanavir
  • ATZ
  • Reyataz®

Brand Names Associated with Tadalafil

  • Adcirca®
  • Cialis®
  • Entadfi® (as a combination product containing Finasteride, Tadalafil)
  • Tadalafil

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Last updated Feb 29, 2024

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Interaction Effect

Increased tadalafil bioavailability

Interaction Summary

Coadministration of atazanavir (a potent CYP3A4 inhibitor) and tadalafil (a CYP3A4 substrate) may result in increased tadalafil exposure. Compared with tadalafil alone, the addition of ritonavir (single agent) increased tadalafil AUC by 124%. While interaction studies of tadalafil and atazanavir have not been performed, other protease inhibitors are expected to cause increased tadalafil exposure[1]. In patients treated with tadalafil for pulmonary hypertension, discontinue tadalafil for at least 24 hours before initiating atazanavir and wait least 1 week after initiation of atazanavir before initiating/reinitiating tadalafil 20 mg once daily (may increase to 40 mg once daily if tolerated). If the patient has already been receiving atazanavir for more than 7 days, initiate tadalafil 20 mg once daily and increase to 40 mg once daily based on tolerability. During concomitant use with atazanavir in patients treated with tadalafil as needed for erectile dysfunction (ED), initiate tadalafil at 5 mg and do not exceed the maximum recommended dose of 10 mg every 72 hours. For treatment of benign prostatic hyperplasia, do not exceed tadalafil 2.5 mg/day in patients receiving atazanavir concomitantly. Monitor patients for increased tadalafil side effects (hypotension, syncope, prolonged erection) [2][3].

Severity

Major

Onset

Unspecified

Evidence

Theoretical

How To Manage Interaction

Concomitant use of atazanavir, a strong CYP3A4 inhibitor, and tadalafil, a CYP3A4 substrate, may result in increased tadalafil exposure[3]. In patients treated with tadalafil for pulmonary hypertension, discontinue tadalafil for at least 24 hours before initiating atazanavir, and wait at least 1 week after initiation of atazanavir before initiating/reinitiating tadalafil 20 mg once daily (may increase to 40 mg once daily if tolerated). If the patient has already been receiving atazanavir for more than 7 days, initiate tadalafil 20 mg once daily and increase to 40 mg once daily based on tolerability. During concomitant use in patients treated as needed for erectile dysfunction (ED), initiate tadalafil at 5 mg and do not exceed the maximum recommended dose of 10 mg every 72 hours. For treatment of benign prostatic hyperplasia, do not exceed tadalafil 2.5 mg/day in patients receiving atazanavir concomitantly. Monitor patients for increased tadalafil side effects (hypotension, syncope, prolonged erection) [2].

Mechanism Of Interaction

Inhibition of CYP3A4-mediated tadalafil metabolism by atazanavir

Literature Reports

A) Although the interaction between atazanavir and tadalafil has not been studied, coadministration of a single dose of tadalafil 20 mg with ritonavir 200 mg increased tadalafil AUC by 124% compared with tadalafil alone. When coadministered with ritonavir 500 mg or 600 mg twice daily at steady state, tadalafil AUC increased by 32%, with a 30% decrease in tadalafil Cmax compared with tadalafil alone [1].

References

    1 ) Product Information: ADCIRCA oral tablets, tadalafil oral tablets. Eli Lilly and Company, Indianapolis, IN, 2011.

    2 ) Panel on Antiretroviral Guidelines for Adults and Adolescents: Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. AIDSinfo, U.S. Department of Health and Human Services. Rockville, MD. 2013. Available from URL: http://aidsinfo.n... . As accessed 2013-02-12.

    3 ) Product Information: CIALIS(R) oral tablets, tadalafil oral tablets. Lilly USA, LLC (per manufacturer), Indianapolis, IN, 2011.

Atazanavir Overview

  • Atazanavir is used along with other medications to treat human immunodeficiency virus (HIV) infection in adults and children who are at least 3 months of age and weigh at least 22 lb (10 kg). Atazanavir is in a class of medications called protease inhibitors. It works by decreasing the amount of HIV in the blood. Although atazanavir does not cure HIV, it may decrease your chance of developing acquired immunodeficiency syndrome (AIDS) and HIV-related illnesses such as serious infections or cancer. Atazanavir must be given with other medications that treat HIV infection to completely treat the infection. Taking these medications along with practicing safer sex and making other lifestyle changes may decrease the risk of transmitting the HIV virus to other people.

See More information Regarding Atazanavir

Tadalafil Overview

  • Tadalafil (Cialis) is used to treat erectile dysfunction (ED, impotence; inability to get or keep an erection), and the symptoms of benign prostatic hyperplasia (BPH; an enlarged prostate) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency in adult men. Tadalafil (Adcirca) is used to improve the ability to exercise in people with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of breath, dizziness, and tiredness). Tadalafil is in a class of medications called phosphodiesterase (PDE) inhibitors. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Tadalafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow more easily.

  • If you are taking tadalafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Tadalafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus (HIV).

See More information Regarding Tadalafil

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.


Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.


Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.


Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.