What medications have unexpectedly caused alopecia or changes in hair growth?

From the Guidelines

Chemotherapy-induced alopecia (CIA) and endocrine therapy-induced alopecia (EIA) are two common types of hair loss caused by medications, with CIA typically resulting in diffuse grade 2 alopecia on the entire scalp, and EIA characterized by grade 1 alopecia primarily on the crown of the scalp. Several medications can unexpectedly cause changes in hair, including:

• Chemotherapy drugs such as doxorubicin and cyclophosphamide, which typically cause rapid hair loss within weeks 1
• Endocrine therapies, such as aromatase inhibitors (AIs), which can cause grade 1 alopecia primarily on the crown of the scalp 1
• Other medications that may affect hair include anticonvulsants, immunosuppressants, hormone therapies, and antimalarials These medications affect hair by disrupting the normal hair growth cycle, often pushing follicles into a resting or shedding phase. Some medications can also cause excessive hair growth in androgen-dependent areas of the body in women, such as hirsutism 1. It is essential to note that hair changes are usually reversible once the medication is discontinued, though recovery may take 3-6 months. If you experience significant hair changes while on medication, consult your healthcare provider before stopping any prescribed treatment, as they may adjust dosages or suggest alternative medications with fewer hair-related side effects. In patients presenting with EIA, differential diagnoses should be ruled out by laboratory testing and examination for female-pattern hair loss, alopecia areata, or inflammatory (scarring) alopecia 1.

From the Research

Medications Causing Alopecia or Changes in Hair Growth

• A variety of medications have been reported to cause alopecia or changes in hair growth, including:
  • Antimitotic agents, which can cause irreversible baldness 2
  • Psychotropic drugs, such as tricyclic antidepressants and lithium, which can cause hair thinning 2
  • Anticonvulsant agents, such as valproic acid, which can cause hair loss 2
  • Antihypertensive drugs, such as beta-adrenoceptor antagonists, which can cause hair loss 2
  • Salicylates and nonsteroidal analgesics, which can cause hair loss in a small percentage of patients 2
  • Anticoagulant and antithyroid drugs, which can produce hair loss 2
  • Oral contraceptives, which can cause diffuse hair loss while receiving the pill and after stopping the drug 2
  • Cimetidine, retinoids, amphetamines, bromocriptine, and levodopa, which have been cited as causing hair loss on occasion 2
  • Hypocholesterolaemic or anti-infectious agents, which have been reported to cause hair loss in isolated cases 2
  • Warfarin, which can cause alopecia by promoting the 'resting phase' of hair follicles 3

Mechanisms of Drug-Induced Hair Loss

• Drugs can interfere with the hair cycle and produce hair loss through different mechanisms, including:
  • Anagen effluvium, which is a prominent adverse effect of antineoplastic agents 4
  • Telogen effluvium, which can be caused by a large number of drugs, including anticoagulants, retinol, and antihyperlipidaemic drugs 4
  • Anagen arrest, which can be caused by certain medications 5
  • Accentuation of androgenetic alopecia by androgens 5

Reversibility of Drug-Induced Hair Loss

• Drug-induced hair loss is usually reversible after interruption of treatment 2, 4
• However, some drugs may cause permanent hair loss, and the prevalence and severity of alopecia depend on the drug and individual predisposition 4