Often—actually, far too often—patients come in at the last minute to fill a prescription that has no more refills left, which means their pharmacist needs to contact the doctor’s office to authorize additional refills.

Sometimes we make it, and sometimes we don’t. And therein lies the lesson for today. If you come in afternoon on a Friday in that situation asking a pharmacist for a prescription with no refills, the probability is that we’re not going to be able to reach your physician, which means you may go home empty-handed.

On some occasions, as a courtesy–and let me stress the word courtesy–pharmacists will give patients enough medication to get them through the weekend, but that depends on the medication. If it’s a narcotic or a steroid or if it’s very expensive, the pharmacist simply may not be able to accommodate you.

So, here is my advice. Plan ahead. Call at least three business days in advance of running out of your medication to have the prescription refilled. Another option is to enroll in your pharmacy’s auto refill program. In this plan, certain medications will automatically generate a request to the doctor’s office for a refill when you have no more refills left.

Q. I went to the pharmacy the other day and they wouldn’t fill my prescription for Percocet. In fact, it was the third pharmacy I had gone to that day, and none of them would fill it. What in the world was the problem?

A. Percocet is designated by the federal Drug Enforcement Agency (DEA) as a Schedule II drug. As such, there are strict requirements that must be met in order to dispense this medication. My guess is that your prescription had problems. For instance, the doctor’s name may not have been printed legibly. The doctor’s DEA number may have been missing or the directions may have been unclear. This would require the pharmacist to contact the physician, and if the physician was unreachable, the pharmacist, by law, couldn’t proceed. So, here’s my advice to anyone taking Schedule II drugs, such as Percocet, Adderall, Concerta or Oxycotin. I strongly advise that you present the prescription at a time when the doctor can be contacted to answer any questions that might keep your prescription from being filled. Otherwise, you may have problems getting it filled.

Q. I take vitamin D, as do many of my friends. Should we worry about taking too much?

A. Not really. While appropriate doses vary widely, from 400 international units to 50,000 international units per day, toxic reaction is rare. General doses for adults are 1,000 to 2,000 units a day. Here’s a warning for parents, though. Don’t use vitamin D liquids dosed as 400 IU per drop. Giving one dropperful by mistake can deliver 10,000 units, which would be a bad thing.

Q. I took 800 milligrams of Motrin in the morning for a headache. I took another 600 milligrams in the afternoon. My headache was still not gone. How much more Motrin can I take?

A. The maximum daily dose for over the counter Motrin (ibuprofen) is 1,600 milligrams. Better yet, I suggest alternating between acetaminophen, the generic version of Tylenol, and ibuprofen.

Q. I know people say brand and generic are the same thing, but I am not so sure. If they are the same, why is the generic so much cheaper?

A. Generic and brand name drugs have the same active ingredients. Before a generic drug can be put on the market, it has to meet the U.S. Food and Drug Administration approval that it functions exactly as the name brand. Brand names are more expensive because the manufacturer is charging for name identification.

Q. How do I tell the difference between a cold and the flu, and what do I do if I get either?

A cold goes through phases. A sore throat is usually the first sign and then it progresses to runny nose, watery eyes, sneezing and ends with a cough. The duration is seven to 10 days. For the sore throat, take acetaminophen, a pain reliever. Take an antihistamine to combat runny nose and sneezing. Take an expectorant, such as Robitusin, to relieve chest congestion. Drink plenty of fluids and get rest. The flu, on the other hand, has more intense symptoms. Along with the runny nose, watery eyes, sneezing and cough that accompany colds are nausea, fever and body aches. The best treatment is prevention – get your flu shot. Treatment is rest, lots of fluids and possibly a prescription for Tamiflu.

Dr. Daphne Bernard,Pharm,D.,is a registered pharmacist in Maryland, Virginia and the District of Columbia. She is currently assistant dean at the Howard University School of Pharmacy and a member of numerous boards and associations, including the Association of Boards of Pharmacy, the District of Columbia Board of Pharmacy, the Nonprescription Medicines Academy, Rho Chi Honor Society, American Society of Health-System Pharmacists, American Pharmaceutical Association and the American Association of Colleges of Pharmacy, Please email her at questions@askyourpharmacistrx.com.