It is better to split it into four and take 1.25mg a day. Finasteride has a relatively short half-life, and if you take 5mg every four days, your DHT levels will not be steady but will be fluctuating. This will end up being less effective as a treatment for male pattern baldness than taking 1mg or 1.25mg daily. Additionally, you could have side-effects from not having a steady hormone balance. Splitting the pill will not effect its efficacy, although you should make sure that your pills, and especially the quartered pieces of those that you have split, are stored in an airtight, dry, and dark environment, and are not exposed to extreme temperatures.
