Q: I seldom drink coffee, preferring to stick with herbal tea in the morning. However, I do wonder if coffee interacts with medications. Watching my neighbor take a handful of pills at breakfast inspired this question.

A: Coffee, or more specifically caffeine, does interact with a number of medications. Some worrisome combinations include the heart drug amiodarone, antibiotics such as ciprofloxacin and the heartburn medicine cimetidine.

Coffee contains so many other active ingredients besides caffeine that it may interfere with the absorption of medications like levothyroxine (Synthroid) pills to treat hypothyroidism. Coffee can also reduce the absorption of iron supplements.

Because there are so many potential interactions with common medicines, we would encourage coffee lovers to check with their pharmacist to find out if there are any problematic combinations.

Q: I recently had a terrible upper respiratory tract infection. It came with bronchitis and a cough. Two days after the diagnosis, my cough was much worse, and I had a sore throat.

The PA gave me a Z-Pak and told me to use Vicks VapoRub on my chest and on the soles of my feet. I replied that I had used Vicks for years but never on my feet and inquired what it did. She said it helps open the breathing passages.

A: We are intrigued that a health professional adopted a remedy we have been writing about in The People’s Pharmacy for years. We first heard about this approach from a nurse who had learned about the remedy when her young children had a bad nighttime cough.

We suspect that the menthol in Vicks actually makes you feel better without opening the airways very much. Menthol activates a transient receptor potential (TRP) channel called TRPM8. This is used to perceive cold, which is why menthol feels cooling.

Scientists tested the impact of menthol on upper airway resistance and found that it does not have an effect (Canadian Respiratory Journal, January-February 2013). On the other hand, feeling cooler makes breathing easier. And because there are TRPM8 channels in the skin of the feet, it might explain why putting Vicks on your soles can help.

Q: I had a very stubborn, painful crack at the corner of my thumb. The first-aid creams, ointments, hand creams and lip balms I tried were not very effective. The skin kept splitting.

My daughter suggested coconut oil, and it worked! I found a small jar for about $1 that lasted well over a year. I applied it to the crack after handwashing, at bedtime and any time it bothered me. On that regimen, the crack disappeared in about a week. The oil is solid at room temperature but melts on contact with skin.

A: Dry skin during the winter can lead to painful cracks around nails. Protecting hands from detergent can help somewhat. Finding an effective moisturizer is a great second step.

Coconut oil works well and may also discourage the growth of bacteria that could contribute to cracks. Because this oil is quite greasy, you may wish to wear gloves to keep the oil in contact with your skin as much as possible, especially when sleeping.

In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email them via their website: www.PeoplesPharmacy.com.