Is there an interaction between minoxidil and chemotherapy?

From the Guidelines

There is no direct evidence of a significant interaction between minoxidil and chemotherapy, but caution is advised due to the potential for increased toxicity or decreased efficacy of chemotherapy. Minoxidil, commonly used for hair loss treatment in topical forms (2% or 5% solutions), has not been shown to significantly interfere with most chemotherapy regimens 1. However, patients undergoing chemotherapy should consult their oncologist before using minoxidil, as individual chemotherapy drugs may have specific interactions. Some oncologists recommend waiting until chemotherapy is completed before starting minoxidil, particularly since chemotherapy-induced hair loss is typically temporary and resolves after treatment ends. The theoretical concern is that minoxidil works by increasing blood flow to hair follicles and promoting cell proliferation, which could potentially interfere with chemotherapy's mechanism of targeting rapidly dividing cells. Additionally, patients with compromised immune systems during chemotherapy may be more susceptible to side effects from topical medications. Systemic absorption of topical minoxidil is minimal but not zero, so this remains a consideration. Oral minoxidil, which has higher systemic absorption, would warrant even greater caution during active chemotherapy treatment.

Key Considerations

• The lack of direct evidence on the interaction between minoxidil and chemotherapy means that caution should be exercised, prioritizing the patient's safety and the efficacy of their cancer treatment.
• The potential for drug-drug interactions, as discussed in the context of HIV treatment and chemotherapy 1, highlights the importance of careful consideration and consultation with healthcare professionals before initiating any new medications, including minoxidil, during chemotherapy.
• The guidance on managing potential drug-drug interactions in the context of cancer treatment and antiretroviral therapy 1 can inform the approach to minimizing risks when considering the use of minoxidil alongside chemotherapy.

Recommendations for Clinical Practice

• Patients should consult their oncologist before using minoxidil during chemotherapy to assess potential risks and benefits.
• Oncologists should consider the individual chemotherapy regimen and the patient's overall health status when advising on the use of minoxidil.
• Given the minimal systemic absorption of topical minoxidil, it may be considered safer than oral minoxidil, but caution is still necessary.

From the FDA Drug Label

Minoxidil topical solution 5% will not prevent or improve hair loss which may occur with the use of some prescription and non-prescription medications, certain severe nutritional problems (very low body iron; too much vitamin A intake), low thyroid states (hypothyroidism), chemotherapy, or diseases which cause scarring of the scalp

There is an interaction between minoxidil and chemotherapy in that minoxidil will not prevent or improve hair loss caused by chemotherapy. 2

From the Research

Interaction between Minoxidil and Chemotherapy

• There is evidence to suggest that minoxidil can interact with chemotherapy, specifically in the context of chemotherapy-induced alopecia [ 3 ].
• A randomized trial found that topical minoxidil decreased the duration of alopecia caused by chemotherapy, with a statistically significant difference in the interval from maximal hair loss to first regrowth [ 3 ].
• Another study reported the case of a patient with chemotherapy-induced alopecia who was treated with oral minoxidil with good results, suggesting a potential interaction between minoxidil and chemotherapy [ 4 ].

Safety and Efficacy of Minoxidil in Chemotherapy-Induced Alopecia

• The studies suggest that minoxidil can be effective in reducing the duration of chemotherapy-induced alopecia, with no significant side effects reported [ 3 , 4 ].
• However, another study found that low-dose oral minoxidil therapy was not associated with an increased prevalence of pericardial effusions in patients with alopecia [ 5 ].

Combination Therapy with Minoxidil

• Some studies have investigated the use of minoxidil in combination with other therapies, such as laser and light therapy, for the treatment of alopecia areata and female pattern hair loss [ 6 , 7 ].
• These studies suggest that combination therapy with minoxidil may be effective and safe for the treatment of alopecia, but more high-quality trials are required for comprehensive analysis and further verification [ 6 , 7 ].