With new medications arriving on the market all the time that patients may be unfamiliar with, prescription requests are often accompanied by a flurry of questions. Understandably, the prescribing doctor does not always have the time to go through all the side effects of the medications. Part of our function as dispensers is to provide answers to questions and share evidence-based resources. Medication-induced hair loss is one of the most common subjects we deal with. This article aims to provide a comprehensive overview of the most common questions in this area.
Please keep in mind that serious concerns about medications should be discussed with the prescribing doctor because there are no hard-and-fast rules that can predict whether or not a specific drug will induce hair loss in a person. Everyone reacts differently to medications, so it’s impossible to state unequivocally that a side effect will or will not occur for any particular individual. This piece addresses the more commonly reported results. Â
A short introduction to the cycle of hair growth and loss
There are two main types of hair. The more visible, longer, and thicker hair is called terminal hair. It covers about 90% of the body in adult men and about 30 percent of the body’s surface in adult women. It is found mostly on the head and face and forms eyelashes, eyebrows, pubic, chest, and belly hair. There are also shorter and thinner vellus hairs on the body, sometimes called peach fuzz. This article mainly addresses terminal hair. We will be focusing on the scalp since this is the main area of concern regarding hair loss as a side effect of medications. There are some instances where hair loss can occur in other parts of the body. Still, usually, this happens along with scalp hair loss, so understanding medication-induced hair loss on the scalp should be enough to cover all aspects of body hair loss.What is the main hair growth cycle?
New cells are constantly forming in the hair follicles. About one million hair follicles are in the top two layers of skin covering the scalp. Individual follicles usually live for between seven and eight years. A follicle comprises a group of cells forming a tube-like pore. The cells stick together and harden. The full strand of hair grows from this group of hardened hair cells. While the root is active, hair growth occurs in a continuous process characterized by four phases:- Anagen – Growth of hair. In this phase, new hardened cells attach to the hair strand from below, so it is gradually being pushed out of the skin.
- Catagen – Regression of the follicle. This phase usually lasts two weeks, during which hair growth slows down and finally stops. The hair follicle detaches from the blood supply, leading to the formation of a new follicle in the root. The hair strand is no longer actively growing during this phase. It loses 20-30% of its diameter but remains firmly anchored in the hair follicle.
- Telogen – The resting phase, which can last several months. Without blood supply, the hair strand is gradually pushed out and finally falls out. A new hair strand then starts to form at the base of the “empty” hair follicle to form a new hair, and the growth phase of the hair growth cycle starts all over again.
- Exogen – The shedding phase. This phase is (basically) the final part of the telogen phase. Hair strands are released from the hair follicles while new hairs are growing in the follicles. It’s to be expected that as many as 100 hairs may fall out each day, which is normal daily hair loss.
How do medicines affect hair health?
Some medications can lead to hair loss as a side effect. This occurs mostly when a drug interferes with the normal cycle of scalp hair growth. The different types of influence depend on the mechanisms of the drug. The main effects are:- Slowing down the growth phase (anagen)
- Causing more hairs than usual to enter the resting (telogen) and falling out (exogen) phases
- Directly damaging the hair follicles.
- Anagen effluvium occurs during the hair’s growth phase, often due to medications that affect cell reproduction, such as chemotherapy agents, resulting in significant hair loss.
- Telogen effluvium, sometimes referred to as hair shedding, is the most common type of medication-induced hair loss. It involves premature shifting of hair from the growth phase to the resting phase, leading to shedding.
Which medications are known to cause hair loss through anagen effluvium?
Chemotherapeutic drugs are a major cause of hair loss. According to the article dealing with Anagen Effluvium on the National Library of Medicine website, the condition is often referred to as chemotherapy-induced alopecia, as it can be triggered by the types of drugs administered as chemotherapeutic therapy, specifically antimetabolites, mitotic inhibitors, and alkylating agents. Some specific examples are- Nexavar – Prescribed to treat patients with advanced kidney, liver, or thyroid cancers
- Femara – Treats estrogen receptor-positive cancers in postmenopausal women
- Nolvadex-D – Treats advanced breast cancer in men and women and early breast cancer in women.
Is medication-induced hair loss permanent?
In many cases, hair loss from medication is not permanent. Hair can usually grow back once the medication causing the problem is stopped or changed. While preventing hair loss caused by medication might not be entirely possible, steps can be taken to minimize the impact (assuming that the treating physician does not recommend switching to a different medication).Steps to minimize medication-induced hair loss:
- Try to maintain a balanced diet that is rich in the vitamins and minerals that support hair health.
- Avoid aggravating the effect of any medications by avoiding hair styling practices that can stress the hair follicles, such as heat styling, and harsh chemicals, such as formaldehyde, used in keratin hair-smoothing treatments. Limit styling that pulls on the hair roots with tight braids, cornrows, dreadlocks, hair extensions, or weaves.
- If undergoing chemotherapy, there are cooling caps that can be worn during chemotherapy sessions to reduce the risk of hair loss.
