Pharmacogenomics shows promise in guiding dosages
Question: Do you have any information on cytochrome P450 testing for drug sensitivity? — S.S.
Answer: Cytochrome P450 is a family of enzymes that are important for cell metabolism and critical for detoxifying many drugs. Any given person has a particular set of
P450 enzymes, and understanding them sometimes can help determine the correct exact drug dosages. In a few cases, people with certain P450 enzymes cannot safely take some drugs. However, the clinical usefulness of P450 testing is currently limited, and there are only a handful of drugs for which testing is recommended (for those who want to see the full current list, it’s available on the Food and Drug Administration website at https://tinyurl. com/P450drugs). The majority of the drugs for which P450 testing is recommended are for HIV or cancer treatment. Physicians prescribing these drugs would order the appropriate testing.
I do think that this field, called pharmacogenomics, is going to become increasingly useful, and it is likely that it will be used to more precisely guide drug choices and dosages.
Q: My husband bought a used car about two years ago, and every time I ride in his car — no matter the time of day or where we are going — about 10 minutes into the ride, I begin to yawn uncontrollably. These are deep, shuddering yawns that border on painful. Soon thereafter, my nose begins to run, my eyes water and my throat becomes scratchy. Allergies seem the obvious answer, but I have a lot of allergies that don’t cause yawning. The yawns are very uncomfortable! Do you have any advice, other than taking my car all the time? — E.R.
A: Well, before today,
I’d never heard of yawning being a sign of allergies. I was able to find other case reports of people having yawns as an initial symptom of allergies.
If avoiding the offending agent (i.e., whatever is in the car) isn’t possible, premedicating with an antihistamine or prescription medication may be of benefit.
Q: I am a 78-year-old male in good health. This past June, my urologist gave me a test, which revealed that I was at very low risk for prostate cancer. Since then, my numbers have gradually crept up, and the most recent test (a month ago) showed a sharp spike upward. The doctor has scheduled a prostate biopsy in two weeks. I am thinking that I would like another blood test prior to the procedure. — R.S.
A: You likely are talking about the PSA test or a relative. I do think confirming the test results prior to biopsy is reasonable, as there are rare lab errors, but more commonly, men can develop inflammation in the prostate, causing a “spike” in the reading. There are several new tests that may improve the accuracy of the PSA. Perhaps the best-known is the PCA3.