Minoxidil was originally designed as a blood pressure med and was found to support hair growth. Kind of like Viagra was designed for pulmonary hypertension and it was later found that it supported erections.

The doses of minoxidil given to support the anagen or thicker phase of hair growth {2.5 to 5 mg) are much lower than those given for blood pressure (10 to 20 mg). The higher doses are more commonly associated with side effects like lightheadedness, palpitations, lower extremity edema and pericardial effusion.

Detasteride or Finasteride decrease the conversion of testosterone to dihydrotestosterone. Scalp DHT accelerates follicle minituarization. This medication has a long half life so if youve taken it for weeks it stays in your system for weeks even after youve stopped it. There are people that have reported longer standing mood changes due to this drug.

I know many who tolerate both just fine but everyone should assess their own risk tolerance and make a decision based on that. The topical formulations help but the oral combination is much more effective and for those that pursue a hair transplant these meds will always be started afterwards (often beforehand as well) because otherwise your DHT will just wipe out the transplanted follicles.