Count your pills after the prescription is filled. Anyone, even pharmacists, can lose count. Read the warnings included in your prescription sack. Some drugs can't be taken with others. Know the prescription's limits concerning your lifestyle.
Public libraries have a reference volume of the current year's Physician's Desk Reference.
This book contains current prescription information. Any drug available is in this volume. This is the same book your doctor uses in his office. Look in the index for the drug's name and xerox the information you find. Study it at home to ascertain if there are more warnings and danger signals you need to know.