DEAR DR. ROACH: My husband’s urologist put him on trimethoprim for a urinary tract infection. He was on this medication for 90 days and was then told to take it another 90 days. Upon reading more about this drug, we found that it should be taken for only 10 days.

After going for a blood test recommended by our primary care physician, not the urologist, my husband was diagnosed with myelodysplastic syndrome. We read that this is a possible side effect of the drug.

My husband had to undergo a bone marrow biopsy, and is under the care of an oncologist. We are taking a “wait and see” approach to his MDS. He has a low-grade MDS, and so he is going to get his blood tested every two months rather than start on Procrit to raise his blood count, as it also has dangerous side effects.

Do you have any advice? — A.L.

ANSWER: The myelodysplastic syndromes are a group of related illnesses in which the bone marrow is unable to provide adequate red blood cells, white blood cells or platelets. These diseases are caused by genetic mutations, some of which may be inherited; others may come as a result of damage to DNA, such as by chemotherapy and radiation. Trimethoprim (which almost always is combined with sulfamethoxazole) is a broad-spectrum antibiotic that does have the possible side effect of causing damage to bone marrow. Bone marrow damage from trimethoprim has some resemblance to myelodysplastic syndromes, but trimethoprim does not cause MDS.

Although there is no cure for MDS, people with “low grade” MDS may live many years without needing treatment. A complete discussion of the treatment options for MDS is beyond the scope of this column, but the goals of treatment are to control symptoms and to improve the quality of life. Transfusions and bone marrow-stimulating drugs like erythropoietin (Procrit) often are used, but may not be needed for years.

DEAR DR. ROACH: I recently read to be aware of dangers when eating canned tomatoes from dented cans. A new salvage grocery has opened locally and features many items that are dented, crushed packages or slightly out of date. Many of these items are still good, and offer an opportunity to save money.

As a home gardener, I realize that it’s much easier to buy a dented can of tomatoes for a very small price than to spend hours canning tomatoes. Is it safe? — M.K.

ANSWER: With damaged cans, our concern is for the toxin from a bacterium, Clostridium botuli, which causes the disease botulism. Botulism is extremely rare, but is higher in low acid or tomato-based foods. The U.S. Department of Agriculture recommends discarding any cans with deep dents (those with sharp edges), because they may contain holes that allow the bacteria to enter. Also, any can that lets out contents or gas when opening should be discarded without tasting. Small dents are generally not worrisome.

Home canning is associated with a higher risk of botulism, as inexperienced home canners may not strictly follow safe canning techniques.

The expiration date on a shelf-stable food like canned tomatoes refers to quality, not safety. In other words, although it is still safe to consume, it may not have the same quality after its expiration date.

READERS: The booklet on stroke explains this condition that is deservedly feared by all. Readers can obtain a copy by writing: Dr. Roach Book No. 902, 628 Virginia Dr., Orlando, FL 32803. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

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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 ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.