DEAR DR. ROACH: I am a 71-year-old man with a physically active lifestyle, and I have a strong passion to control my A1C and cholesterol levels by eating the right kind of food. I am taking metformin, atorvastatin and losartan to assist in controlling my blood sugar, cholesterol and blood pressure.

After turning 70, I was having difficulty being intimate with my wife. I requested my internal medicine doctor (a friend) to prescribe sildenafil, but he ignored the request. So, I turned to an online pharmacy. After answering a few questions, they dispensed 20-mg tablets. I determined that I needed 40 mg to assist me, and it has been working very well.

I only take 40 mg of sildenafil once a week. I do not have any side effects from any medications that I take. My question: Is there any consequences with taking this medication? As I get older, do I have to increase the dosage? — D.M.

ANSWER: Sildenafil (Viagra when used for erectile dysfunction and Revatio when used for pulmonary hypertension) works by changing the blood flow to certain blood vessels by blocking an enzyme called phosphodiesterase 5. In the penis, this opens up the blood flow going into the penis and constricts the blood flow going away from the penis.

Sildenafil is generally safe, but like any drug, it has the potential for side effects. Vision and hearing changes are well-known but uncommon side effects of sildenafil; they are almost always reversible. Sildenafil cannot be taken by people using any form of nitroglycerine, such as isosorbide mononitrate (Imdur) and isosorbide dinitrate (Isordil). Together, nitrates and sildenafil cause excessive blood vessel dilation with the risk of dangerously low blood pressure levels.

Long-term side effects from the continued use of sildenafil and similar drugs are very unusual. In a study of 1,000 men taking the medicine for four years, there were no serious side effects that required a dosage change or stopping the medicine. Most people continue to get good results at the same dosage.

The dosage you were prescribed is specific for the treatment of pulmonary hypertension. The Food and Drug Administration approved that the dosing for erectile dysfunction is 25-100 mg, so the 40 mg you are taking is a relatively low dose. Billions of doses have been taken worldwide, so there is a lot of clinical experience with this drug.

Getting the prescription from the doctor who knows you is preferred to an online doctor who doesn’t, but having a friend for a doctor can make getting this prescription awkward.

DEAR DR. ROACH: Recently, you wrote about hyaluronic acid supplements. Should I avoid these, as I have an intraductal papillary mucinous neoplasm (IPMN)? — M.P.A.

ANSWER: An IPMN is a tumor of the pancreas that can variably lead to pancreatic cancer depending on its characteristics. A 2022 study showed that pancreatic cancer cells use hyaluronic acid as a fuel source, so I understand why you might be concerned.

The vast majority of hyaluronic acid is made by the body. Hyaluronic acid is essentially produced by all human cells, but found in high concentrations in the eye and joints.

I doubt that supplemental hyaluronic acid will have any impact on the likelihood of an IPMN leading to cancer, but I understand why a person with an IPMN would want to avoid this supplement. People who have IPMNs are usually followed up with imaging, such as an MRI or a CT scan, to look for changes.