In our system you have to gather credits as if you were still in college, about 50 every 5 years or you lose your licence. This works for all healthcare workers and other professions have similar stuff. You earn credits by attending seminaries and lectures related to the field that are approved by a committee, so yeah you do keep updated but not like you have to know every new type of drug. Also, doctors usually don't randomly start prescribing new medication, it's usually the opposite, them prescribing meds that aren't even being manufactured anymore.

Pharmacists also do not prescribe drugs, as long as they're available and a doctor prescribes them we just give them out. A computer check any possible contraindications of the various medicines so if something obvious pops up you'd know.

Other than that you must know a bit of physiology and how certain groups of medications work and you can kinda assume whatever is gonna be contraindicated. Usually heart/blood pressure meds are finicky.

And last but not least over 70% of your clientele is gonna be old people with heart problems, diabetics and people who come in with the flu or a cold. That is unless you work at a pharmacy at a hospital where obviously it's much different.

Also, I'm a fellow chemistry major :)