Finasteride and MPB Myths

Myth: Finasteride is dose dependent for the treatment of MPB

Not really. The effective dose of finasteride to prevent MPB is not directly proportional, because the action of finasteride in the scalp is not directly dose dependent. Finasteride benefits the treatment of MPB by forming a tight chemical bond with the type 2 5-alpha reductase enzyme, which is responsible for converting testosterone into dihydrotestosterone (DHT). However, the 5-alpha reductase enzyme in the scalp is primarily the type 1 5-alpha reductase, which is unaffected by finasteride. With the use of 1mg finasteride daily, the level of circulating DHT is lowered by 60% to 80%. On the other hand, the amount of DHT in the scalp as reported by Merck Pharmaceutical is decreased by only 38%, when daily doses of 5mg finasteride is used, and it is questionable whether increasing the dosage of finasteride causes any significant decrease in the DHT levels in the scalp.

The clinical trials showed that doses between 0.2 mg and 5 mg could have about the same effect on the scalp. That's a very wide range. The 1 mg/day dose is recommended to treat MPB because it encompasses three standards deviations of those being treated and will include ~97% of patients.

Myth: Propecia and Minoxidil will cure MPB

All of the current medications for treating MPB are 'temporary solutions'. They are not cures. We don't have a cure for MPB, but all of the long-term studies show that using topical minoxidil and an agent or agents to reduce the amounts of DHT in the scalp will definitely allow you to keep more of your hair as compared to using a placebo. For now, that's about the best we can do. If you're using a medication to stimulate hair growth (topical minoxidil) and an agent to decrease the DHT in the scalp, you're doing as much as has been proven beneficial to prevent and/or reverse your MPB.

Myth: Shedding is an indication that Propecia is working

It is not normal for Propecia to cause shedding at any time during its use. Binding the type 2 5-alpha reductase does not cause a shift from anagen to telogen, so no shedding would be expected to occur. If shedding does occur, it is not a sign that finasteride is working. There have been rare cases in which patients have reported a telogen effluvium months after initiating treatment with finasteride. Apparently, a drop in the systemic levels of DHT had been the inciting event in causing these cases of telogen effluvium. Although a telogen effluvium usually begins somewhere between 11 and 16 weeks after the inciting event, it can start as soon as 4 weeks thereafter.

There are no specific numbers that we can put on the amount or percentages of hair shed in a telogen effluvium. The amount and degree of hair loss is dependent on the severity of the telogen effluvium. Rarely, will the amount of hair loss exceed 50%. The shedding is generally diffuse (global) and can affect areas of the scalp not usually affected by MPB. So, it would be common to note shedding from the sides and back of the head in addition to the crown, vertex and frontal areas. The shedding tends to be fairly symmetrical, but will be more noticeable in the areas affected by MPB, because there is a higher ratio of hairs in the telogen phase than in the other areas of the scalp not involved with MPB. The shedding lasts about 6 weeks. It usually takes 4 months to a year for the hair to grow back.