Bernstein Medical - Center for Hair Restoration - Medication Half-Life
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Q: First off thank you for providing this Blog, it is extremely informative and gives people the opportunity to ask questions of one of the most knowledgeable hair transplant surgeons in the world. You are considered the consummate researcher in the field of hair loss, so I ask this question of you. It appears that all the current hair loss drugs, at one point or another, begin to lose their effectiveness. Have you ever entertained the idea of cycling these drugs, or reducing the dosage for a period of time, to prevent the body from becoming acclimated to these drugs and subsequently making adjustments to receptors causing this? This method is commonly used by bodybuilders and others in the sports profession to elicit the maximum effect from the drugs they employ. Though I have not found any studies along these lines, I believe there are valid reasons why this may work. I hope you may be able to share any information on this subject. — Z.Z., Chicago, I.L.

A: Excellent question. I can answer it only indirectly.

It has been our experience that when you discontinue finasteride (Propecia), or decrease the dose to a degree that it no longer works, the patient will begin to shed hair. When the drug is re-started or the dose increased again, the medications will begin working, but the patient now maintains his hair at a lower baseline. He doesn’t seem to regain the amount of hair he has before the medication was stopped. For this reason, we don’t stop and start finasteride. The same argument applies to dutasteride, although we have less experience with this medication. This experience would speak against using pulse therapy for hair loss.

On the other hand, the hair loss medications finasteride and dutasteride do not necessarily need to be used once a day. Although the serum half-life of finasteride is around 6 hours, the tissue half-life is felt to be around two days. Therefore, alternate day dosing with 2 mg of finasteride (or approx. 1/2 of a 5mg tablet) should work just as well as 1mg a day. An average daily dose of less than 1mg, however, does not seem to be as effective. Dutasteride has a half-life of 5 weeks and is found to bind to scalp tissue for many months, so with dutasteride, a dosing of even once a week will most likely be just as effective as once a day.

Note that this regular alternate day dosing is different than pulse dosing. In pulse therapy, the body is given a chance to recover. The principle here is to take advantage of the persistence of the drug in the scalp even after blood levels drop and not to let the scalp recover (which we have found to result in a net loss of hair (as discussed above).

When patients do become acclimated to these drugs (which seem to be common after 3 to 5 years) we increase the daily dose of finasteride gradually up to 5mg and then consider switching to dutasteride 0.5mg a day.

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Q: My friend is taking Avodart, he bought it over the internet. Is it safe to take? — T.G., Denver, Colorado

A: Avodart (dutasteride 0.5mg) was approved by the FDA for the treatment of prostate enlargement in men in 2002. Avodart has not been approved for the treatment of androgenetic hair loss, although physicians can use an approved medication in ways other than for which it was specifically approved. That said, the use of dutasteride certainly requires a doctor’s supervision.

Like finasteride (the active ingredient in Proscar and Propecia), dutasteride blocks the enzyme 5-alpha reductase that converts testosterone to DHT (DHT is a key hormone that causes hair loss). However, unlike finasteride, which only inhibits the Type I form of the enzyme, dutasteride inhibits both the Type I and Type II forms. This combined effect lowers circulating DHT more with dutasteride than with finasteride, but also increases the incidence of its side effects.

The Type II form of the enzyme (blocked by finasteride) is found predominantly in the hair follicle. The Type I form of the enzyme has been found in the scalp and sebaceous glands, and many other parts of the body, but its exact role in hair growth has not been determined. It is felt that dutasteride’s ability to dramatically lower serum levels of DHT is what makes it a more potent medication in hair loss.

When considering the safety of dutasteride, one should consider the following:

  • It acts on other parts of the body besides the hair follicle.
  • Unlike finasteride, where families that had a deficiency of the Type II 5-alpha reductase enzyme were followed for years without any adverse effects, there is no natural biologic model to show the safety of dutasteride.
  • Dutasteride has been approved for prostate enlargement in an older male population. It is not approved for hair loss and, in fact, the clinical trials for hair loss were discontinued, so there is no safety data for its use in younger patients. There is a greater incidence of sexual side effects with dutasteride compared to finasteride.
  • The 1/2 life of dutasteride is 5 weeks compared to 6-8 hours for finasteride. Serum concentrations of dutasteride are detectable up to 4-6 months after discontinuation of treatment.
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Q: If Rogaine is used only once a day will it still be effective? — I.P., Hempstead, Long Island, NY

A: Once a day topical use of Rogaine (topical minoxidil 2% and 5%) is probably almost as effective as using it twice a day. The reason is, although minoxidil has a relatively short half-life of several hours when given orally, when topically applied, it has a half-life of 22 hours in the skin.

This suggests that once-a-day dosing is a reasonable option. It is important to realize that Pfizer, the company that now makes Rogaine, specifically states that it will be less effective if used only once a day.

Read about Rogaine (minoxidil)
Read Tips on Using Rogaine

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