Dear Dr. Roach: My wife recently underwent a successful open heart surgery with two valves repaired and one replaced. During her post-surgery recovery, she experienced an issue with the timing of several prescriptions and their impact. We learned that there is a big difference between taking a prescription medicine “twice a day,” versus taking one “every 12 hours.” By the way, the original directions on the prescription simply stated to take it twice daily.
A friend and medical professional educated us on this issue. These terms, although seemingly simple, can have serious ramifications and reduce the intended efficacy. I am sure we are not the only ones who have failed to fully appreciate and understand the distinction between these similar but different expressions.
Perhaps a note to your readers would help others as well, reminding pharmacists, physicians, and physician assistants to be clearer on their directions.
M.B.
When a drug is supposed to be taken “every 12 hours” (or some other number of hours), it implies that the drug needs to be taken precisely at that time interval. Many hospital medicines and a few medicines taken at home need to be dosed exactly. The drug level will be too high, with the possibility of toxicity, if these medicines are taken at a shorter interval than 12 hours. They might become ineffective if they’re taken at a longer interval.
Some antibiotics, seizure medicines and chemotherapy drugs taken at home need to be dosed precisely. Your prescriber and pharmacist should make this clear when prescribing and filling the medication.
“Twice daily” implies that there is some leeway. If you wake up at 7 a.m. and take one dose, then take it again at 9 p.m., you certainly took it twice daily, but the interval has now changed from every 12 hours to 10-hour and 14-hour intervals.
Fortunately, most drugs will still be effective after a longer interval and nontoxic after a shorter one. The vast majority of prescription medications and virtually all over-the-counter medications are safe to take with a slightly uneven interval. Still, you want to keep it as close to the recommended interval as possible. Ask your prescriber if you aren’t sure.
Dear Dr. Roach: Recently, my wife became very sensitive to garlic, to the point where she gets very sick while ingesting even small amounts. She gets abdominal cramping and vomiting, but never any shortness of breath, rashes or lip swelling. Is this an allergic reaction?
A.M.
It could be. Garlic allergies are quite uncommon but are more likely to appear during adulthood than most other food allergies. About half of people with garlic allergies noticed abdominal symptoms like your wife. Other possible reactions include a skin rash, swelling of the lips or tongue, and asthma.
The diagnosis can be made with near certainty by skin testing. About a quarter of people with garlic allergies also showed positive allergic tests to onions, as well as leeks, chives and shallots, which are all closely related members of the Allium family.
Garlic and onions have been used for millennia, especially around the Mediterranean, so garlic is often found in many food products and restaurants. I advise a discussion with the chef prior to ordering any food. Allergies can get worse over time, and avoidance is, by far, the best treatment for food allergies.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected]
