How many times in a week should I wash my hair with Nizoral shampoo for optimum re-growth with 5% Minoxidil and Finastride?

Nizoral (Ketoconazole) 2% shampoo is an antifungal medication which has been proven to have multiple positive effects on the hair itself.   Ketoconazole is effective in reducing scalp inflammation in scalp/skin conditions such as seborrheic dermatitis, dandruff and tinea versicolor.  It has been shown to increase the density of hair as well as increase the population and size of the hair follicles during the growth phase of the hair cycle. Lastly, Ketoconazole has a strong anti-androgen property which is responsible for blocking/inhibition of androgen (testosterone and DHT) receptors.   Using Nizoral shampoo 2-3 times a week is the usual dosage.

using shampoo may keep your hair shaft ph balanced and healthy however there are no evidence that suggests it helps with hair growth. 

Of the three things you are using, the best of course is finasteride. The least effective for hair loss is Nizoral shampoo which is really an anti-dandruff shampoo which for reasons I am not sure, has become part of the hair loss cocktails used today.