Hi,
Welcome to HCM,
Hair loss is common in males with growing age due to male hormone and treatment depends on cause you have already consulted
Dermatologist.
There is no major side effect of local preparation and can use safely.
Finpecia is Finasteride which can have side effects you must know like Impotency,Abnormal ejaculation,
Gynecomastia ( Enlargement of breast)
Testicular pain.
Even though dose is very small still you should discuss with your Dermatologist.
There is small risk of even developing
prostate cancer.
Nizral is anti fungal may be you have dandruff or some other
fungal infection that is why given please continue to use it.
Take care
Good Luck.