Is it safe to switch to procapil after 1 month of using minoxidil? My dr advised me to use procapil in adjunct with minoxidil.

It would be best to ask your doctor about mediation related questions or changing medications.   After all your doctor knows your history and circumstances best. 

In general you should follow your doctor's diagnosis if you trust them. Procapil isn't proven to aid hair like Minoxidil is, but it certainly won't hurt and there shouldn't be any problems with it, especially if Minoxidil is giving you problems. 

        
Procapil is a mixture of vitamins/herbal
supplement, there should be no harm in using both procapil and minoxidil
together as your doctor advised.  Keep in
mind that only minoxidil and finasteride have the FDA approval to treat hair
loss.

The only medications that can slow or stop the progression of hair loss that are FDA approved are finasteride and minoxidil. Procapil is a herbal supplement that has no supported studies of being a preventative medication. If your physician suggested this, please be cognizant of the effects it has on your scalp, and be sure to have follow up.

I always advise patients to follow the advice of their doctors unless you don't trust your doctor's judgment.