Ketoconazole with Isoniazid Interaction Details
Brand Names Associated with Ketoconazole
- Ketoconazole
- Nizoral®
Brand Names Associated with Isoniazid
- Hyzyd®
- INH®
- IsonaRif® (as a combination product containing Isoniazid, Rifampin)
- Isoniazid
- Laniazid®
- Nydrazid®
- Rifamate® (as a combination product containing Isoniazid, Rifampin)
- Rifater® (as a combination product containing Isoniazid, Pyrazinamide, Rifampin)
- Rimifon®
- Stanozide®
- Tubizid®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Dec 02, 2023
Interaction Effect
Decreased ketoconazole exposure
Interaction Summary
Concomitant use of isoniazid and ketoconazole is not recommended and should not be given together as this may cause decreased ketoconazole plasma concentrations resulting in decreased ketoconazole efficacy. Isoniazid is typically used in combination with strong CYP3A4 inducers such as rifampin which may also lead to decreased ketoconazole concentrations and reduced efficacy. Concomitant use of isoniazid and strong CYP3A4 inducers is not recommended and should be avoided within 2 weeks of initiating ketoconazole therapy, unless benefits outweigh potential risks associated with concomitant use. If concomitant use is required, monitor antifungal response as an increase in ketoconazole dosage may be necessary.
Severity
Major
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
Concomitant use of isoniazid and ketoconazole is not recommended and should not be given together as this may cause decreased ketoconazole plasma concentrations resulting in decreased ketoconazole efficacy. Isoniazid is typically used in combination with strong CYP3A4 inducers such as rifampin which may also lead to decreased ketoconazole concentrations and reduced efficacy. Concomitant use of ketoconazole with strong CYP3A4 inducers is not recommended and should be avoided within 2 weeks of initiating ketoconazole therapy, unless benefits outweigh potential risks associated with concomitant use. If concomitant use is required, monitor antifungal response as an increase in ketoconazole dosage may be necessary.
Mechanism Of Interaction
Unknown
Literature Reports
A) Isoniazid can inhibit certain CYP enzymes, including the ones responsible for ketoconazole metabolism. Consequently, ketoconazole metabolism can be reduced and dosage adjustments may be necessary .
B) In one case report, a 55-year-old woman who was taking isoniazid, rifampin and ketoconazole experienced treatment failure after 9 months. Serum levels of all 3 drugs were undetectable, suggesting a drug interaction as the primary cause .
C) A study evaluated the serum concentrations of ketoconazole given alone or with rifampin, isoniazid or both. Concentrations were also measured when ketoconazole was administered 12 hours after rifampin or isoniazid. Serum concentrations of rifampin and ketoconazole were undetectable when all 3 drugs were administered together. When the patient took only isoniazid, the ketoconazole concentration was much lower than when ketoconazole was given alone. No difference was noted when the antimicrobials were given concurrently or 12 hours apart. These results imply that isoniazid interferes with ketoconazole metabolism rather than interacting through gastrointestinal absorption .
Ketoconazole Overview
-
Ketoconazole is used to treat fungal infections when other medications are not available or cannot be tolerated. Ketoconazole should not be used to treat fungal meningitis (infection of the membranes surrounding the brain and spinal cord caused by a fungus) or fungal nail infections. Ketoconazole is in a class of antifungals called imidazoles. It works by slowing the growth of fungi that cause infection.
Isoniazid Overview
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Isoniazid is used with other drugs to treat tuberculosis (TB; a serious infection that affects the lungs and sometimes other parts of the body). Isoniazid is also used with other drugs to treat people with latent (resting or nongrowing) TB including those in close contact with people who have active TB, a positive tuberculin skin test, human immunodeficiency virus (HIV), and those with pulmonary fibrosis (scarring of the lungs with an unknown cause). Isoniazid is in a class of medications called antituberculosis agents. It works by killing the bacteria that cause tuberculosis.
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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.