Finasteride and dutasteride can be used together but only in special circumstances. Finasateride is an inhibitor of the enzyme 5 alpha reductase type 2 and dutaseride is an inhibitor of both 5 alpha reductease type 1 and type 2. Dutasteride is more potent and leads to greater reductions of dihydrotestosterone (DHT). Side effects are also greater with dutasteride than finasteride and likely greater when combining than using alone. One needs to be used FIRST to determine how well ONE works (and generally this is finasteride given that it is FDA approved for hair loss and approved in most countries as well). Studies have shown that some men using finasteride can have enhanced responses by adding small doses of dutasteride (0.5 mg) on the weekend. These were studies by Rod Sinclair and colleagues in 2013. He reported a 47-year-old man who was initially treated with finasteride for male pattern balding. Despite continuous treatment, after year 4 his hair density was not as good as previous years, and low-dose dutasteride at 0.5 mg once per week was added to the finasteride therapy. Interestingly, this resulted in a dramatic increase in his hair density, demonstrating that combined therapy with finasteride and dutasteride can improve hair density in patients already taking finasteride.
