Finasteride and dutasteride together: is it worth it?

Combining two drugs from the same class sounds obvious. What the half-lives say about it, and how thin the evidence really is.

Anyone under treatment for a long stretch who is still losing ground eventually runs into the question of whether both available 5-alpha-reductase inhibitors can be used at the same time. The reasoning is understandable: if both work, both together should work harder.

With drugs that act at different points, that reasoning often holds. Minoxidil and a 5-alpha-reductase inhibitor complement each other because they work in entirely different places. Finasteride and dutasteride do not. They inhibit the same enzyme, with a different profile.

The essential difference is one of time

The two substances differ less in mechanism than in how long they stay in the body. Finasteride is cleared within hours, though its effect on DHT persists for several days. Dutasteride remains in the body for weeks.

That table already contains the most important qualification. The large gap in blood arises mainly from the additional inhibition of the type 1 isoenzyme, which is active chiefly in sebaceous glands and the liver. At the actual site of interest, the scalp, the gap is much smaller. We covered this in detail in our article on finasteride and dutasteride.

Why taking both daily makes little sense

If dutasteride is taken daily, the enzyme is already largely inhibited. Adding daily finasteride then acts at a point with little room left. In that form the combination amounts to much the same as dutasteride alone, using two preparations and carrying two side-effect profiles.

A different variant discussed in practice is more interesting: continuing finasteride daily and adding a single weekly dose of dutasteride. Because dutasteride persists so long, a sustained level remains even with weekly dosing. The idea is to achieve some additional suppression without switching fully to the stronger drug.

How well established is this?

Honesty matters more than optimism here. There are no randomised controlled trials of the two oral drugs in combination. What exists is essentially a single published case from 2012, described by an internationally recognised hair researcher.

It describes a patient who initially responded well to finasteride but began losing ground again after several years. After a weekly dose of dutasteride was added, a marked increase in density appeared within a few months.

When the question is worth raising at all

Before considering an addition, the existing treatment should have been judged fairly. Two points are regularly overlooked.

First, the effect needs time. In the licensing studies, the full effect was in part only reached after around two years. Anyone taking stock at six months is taking stock too early.

Second, increased shedding at the start of treatment is a known and temporary phenomenon, not a sign of failure. We have written about it separately in shedding at the start of treatment.

Talking about an inadequate response only makes sense when visible substance is still being lost after at least twelve months of consistent use, and preferably longer.

More drugs do not automatically mean more result

A pattern is common in hair medicine that rarely serves the treatment: because a therapy is working, the wish arises to achieve ever better results through ever more additions. What ends up in place is an elaborate regimen whose individual components can no longer be told apart.

When a treatment reaches its goal, meaning it halts the loss, that is the success it is meant to deliver. Every addition should have a specific, nameable reason.

Frequently asked questions

This article is for general guidance and does not replace medical advice or diagnosis. The drugs named are available on prescription only and results vary from person to person. Use outside an approved indication is a decision for the treating doctor, made case by case.