Are there any problems taking Azathioprine (AZA) and Minoxidil?

From the Guidelines

Taking azathioprine and minoxidil together requires careful medical supervision due to potential interactions that may increase the risk of certain side effects, particularly if minoxidil is taken orally. While there is no absolute contraindication between these medications, they can both cause side effects that may compound each other. Azathioprine, an immunosuppressant used for autoimmune conditions, can cause bone marrow suppression, liver toxicity, and increased infection risk 1. Minoxidil, whether used topically for hair loss or orally for resistant hypertension, can cause fluid retention, rapid heartbeat, and lowered blood pressure 1. The combination might increase your risk of certain side effects, particularly if minoxidil is taken orally.

Key Considerations

• Regular blood tests to monitor your complete blood count and liver function are important while on azathioprine, and blood pressure monitoring is essential with minoxidil 1.
• Some patients experience increased hair growth with both medications, which could potentially enhance minoxidil's intended effect for hair loss but might also cause unwanted hair growth elsewhere on the body 1.
• Always inform all your healthcare providers about all medications you're taking to ensure proper monitoring and dosage adjustments if needed.
• The dose range of azathioprine given to patients is variable, with most studies choosing a dose range between 1 to 3 mg/kg/day, and it is essential to monitor thiopurine methyltransferase (TPMT) activity level to minimize the risk of adverse effects 1.
• Minoxidil is usually reserved for patients with hypertension that is resistant to multiple drugs, and its use requires careful monitoring of blood pressure and potential side effects such as hypertrichosis 1.

Monitoring and Precautions

• Patients taking azathioprine should be advised to seek urgent medical attention if they develop signs and symptoms of bone marrow impairment or liver impairment, such as unexplained bruising, sore throat, high fever, or jaundice 1.
• Patients taking azathioprine who have not had chickenpox should seek immediate attention if they come into contact with someone who has chickenpox or shingles for consideration of zoster immune globulin 1.
• The combination of azathioprine and minoxidil should be used with caution, and patients should be closely monitored for potential interactions and side effects.

From the Research

Potential Interactions and Side Effects

• There is limited research on the direct interaction between Azathioprine and Minoxidil. However, studies on individual medications provide some insights:
  • Azathioprine is an immunosuppressive drug used in the therapy of autoimmune disorders and in preventing graft rejection 2.
  • Minoxidil is a vasodilatory drug used for treating various forms of alopecia, with low-dose oral minoxidil (LDOM) emerging as an effective alternative to traditional topical minoxidil 3, 4.
• Side effects of Azathioprine include myelotoxicity, gastrointestinal intolerance, and malignancy, with 20.6% of patients experiencing side effects in one study 5.
• LDOM has been shown to have a favorable safety profile, with systemic adverse effects detected in 6.8% of cases, including lightheadedness, fluid retention, and headache 3.
• A study on the long-term safety and effectiveness of Azathioprine in inflammatory bowel disease found that the drug is safe and effective in the long-term, with 76.5% of patients continuing treatment until the last follow-up 5.
• Another study highlighted the importance of monitoring Azathioprine dosing using thiopurine methyltransferase pharmacogenetics and thiopurine metabolite testing to optimize therapy and minimize adverse effects 6.

Blood Pressure Effects

• Low-dose oral minoxidil does not significantly affect blood pressure, according to a systematic review and meta-analysis, with no significant alterations in systolic or diastolic blood pressure 4.
• However, there was a strong tendency toward decreased mean arterial pressure and a significant increase in heart rate 4.
• Hypotensive symptoms were reported in 5.0% of patients, but no hypotensive episodes were observed 4.

Combination Therapy

• There is no direct evidence on the combination of Azathioprine and Minoxidil, and therefore, it is essential to monitor patients closely for potential interactions and side effects.
• Clinicians should be aware of the potential for allopurinol co-therapy with Azathioprine as a useful therapeutic pathway for patients who do not adequately form active thioguanine metabolites 6.