Taking medicine is no fun. Hair loss that may be caused by medication can be additionally distressing. Typically hair will re-grow once the medication is stopped but understanding why medications can cause hair loss may help relieve some concern.
Hair normally grows in three phases.
The first phase is anagen (growth). Hair grows for approximately three to four years.
Then the catagen (cessation) phases follows. This is a transitional stage that last three to four weeks.
Finally, the telogen (resting) phase occurs which lasts about three months. At this time older hairs first rest, then are shed and replaced by new hair.
Medication can affect the hair cycle in one of two phases. Drugs such as chemotherapy medications affect the hair during the anagen phase, while the hair is actively growing.
The hair cell division is interrupted so the hair is lost a few days to a few weeks after receiving the medication. Hair loss in this phase is called anagen effluvium.
The most common type of medication-induced hair loss occurs during the telogen phase. The medication causes the hair to go into the resting stage too early so the hair is lost too early.
Usually hair loss occurs two to four months after taking the medication. Hair loss in this phase is called telogen effluvium.
The amount of hair loss may depend on the dose of, or your sensitivity to, the medicine. There are numerous medications that may cause hair loss.
The American Hair Loss Association lists main categories and names of those medications. Refer to their website to see the original list.
Examples of some of the medications are listed below:
- Acne medications or those that contain vitamin A
- Blood thinners
- Cholesterol medications
- Anti-seizure drugs
- Beta-blockers, which are used to treat the heart and high blood pressure
- Drugs that affect hormones such as steroids or birth control pills
- Parkinson’s disease medications
- Thyroid medications
- Ulcer medications