Q: You frequently mention yellow mustard as a possible remedy for muscle cramps. Is there something about yellow mustard in particular that seems to make it work?

A: There have been no scientific studies of any type of mustard to relieve muscle cramps. Hence, there is no way to judge whether Dijon mustard is better or worse than cheap yellow mustard. We suspect that mustard works through the same mechanism as pickle juice, vinegar, cinnamon or cayenne pepper. Mustard oils contain isothiocyanates that activate transient receptor potential channels in sensory nerves in the skin, mouth, throat and stomach (Nature, Jan. 15, 2004). Stimulating these nerves sends out a signal that overrides the inappropriate hyperactivity of nerves causing muscle cramps (Muscle & Nerve, September 2017).

Q: My tennis elbow has come back with a vengeance. I can’t use oral NSAIDS because I take Eliquis, but my primary care physician says I can use the diclofenac sodium topical gel (1 percent) for as long as I need it. She knows I take a blood thinner. Is this really OK?

A: You are right to avoid oral pain relievers such as ibuprofen or naproxen, since these NSAIDs can cause gastrointestinal irritation. With apixaban (Eliquis) in your system, you could end up with a bleeding ulcer. Drug-interaction experts Drs. John Horn and Philip Hansten have written about NSAID and anticoagulant interactions. They note: “The use of topical NSAIDs is not considered to increase the risk of bleeding” (Pharmacy Times, Dec. 21, 2017).

Q: My husband and I returned from a trip to Europe with a strain of the flu apparently not covered by our flu vaccine. We took Xofluza and after three doses, both of us developed diarrhea and abdominal cramping. We stopped taking the meds, and the symptoms stopped. The headache, congestion and body aches of the flu were bad enough without adding the diarrhea caused by expensive meds.

A: Baloxavir (Xofluza) is a brand-new anti-viral flu medicine. This oral medication shortens the duration of flu symptoms when taken within 48 hours of getting sick. We are puzzled why you took three doses. The advantage of this medicine is that it is given as a single dose. The triple dose might have increased your risk for diarrhea, a recognized side effect of Xofluza. The clinical trial data showed that 3 percent of people taking one pill suffered this complication.

Q: You’ve written about cinnamon as a supplement that could help control blood sugar levels. I understood you to say that Cinnamomum cassia has more coumarin than Cinnamomum verum. Coumarin should be avoided because it might harm the liver. The cinnamon I purchased says Cinnamomum burmannii on the label. Do you know how much coumarin there is in this type of cinnamon?

A: Cinnamomum burmannii contains many of the same compounds that provide the familiar cinnamon flavor from cassia cinnamon (Cinnamomum cassia) or Ceylon cinnamon (Cinnamomum verum). C. burmannii has anti-inflammatory activity and can help regulate blood sugar after a meal (Pharmacognosy Review, July-December 2012). You are right that coumarin has the potential to damage the liver. Relatively high levels are found in cassia cinnamon and also in C. burmannii. Since coumarin is not water-soluble, we suggest you make tea or another type of water extract with your C. burmannii. That should provide you with the benefits and minimize the risk of harmful liver effects.

In their column, Joe and Teresa Graedon answer letters from readers. Send questions to them via www .peoplespharmacy.com.