Nizoral itself is a fairly harsh shampoo and is to be used twice a week maximum. The active ingredient in Nizoral, which is Ketoconazole, has been shown to help with hair loss. There are higher levels of Arachidonic Acid in a balding scalp, which is a pro-inflammatory Omega-6 fatty acid, and Ketoconazole helps to treat this issue. Ketoconazole is also a mild anti-androgen, and has local competing effect with Testosterone and other androgens when applied topically to the scalp, it does so very mildly.
Twice a week is the recommendation for dandruff. I believe to get the most out of Ketoconazole for hair loss, you'll probably want to use it daily. Obviously though, Nizoral is harsh and cannot be used everyday. One Ketoconazole shampoo that I myself have liked the most is one called Regenepure DR, it has water and aloe ver gel as its two main base ingredients. It's also 1% Ketoconazole just like Nizoral and is free from sulfates. There are a couple of other good ones which are Lipogaine Big Three Shampoo and Revita. I've tried the Lipogaine Big Three Shampoo and Nizoral before and I like myself personally like Regenepure DR so far the best. I've currently never tried Revita.