Reader questions drug compatibility

Dear Dr. Roach: I was diagnosed with stage 1 bladder cancer in April. My urologist advised me to have BCG therapy for it. I just completed six weeks of the therapy.

I also have macular degeneration in both eyes and have had Avastin injections in my left eye for almost two years. I have had a couple of injections into my right eye, too, the last of which were done in June.

Neither my urologist nor my retina doctor could answer my question about having injections and BCG therapy done at the same time — whether they are compatible and would continue to benefit me. I understand that BCG therapy reduces the recurrence of returning tumors. The Avastin eye injections may keep me from going completely blind. I have made numerous phone calls to different groups asking these questions, but no one has been able to help me. I need an answer, as I am past due for the eye injections and have an appointment this week with the retina doctor.

S.P.

Answer: I don’t have a definitive answer for you, but I’ll share what I know and what I found out.

Avastin (bevacizumab) is an antibody drug that prevents the formation of new blood vessels by blocking vascular endothelial growth factor.

This drug has proven to be useful in some cancers, which cannot grow without adequate blood supply, and in wet age-related macular degeneration, where new blood vessels in the retina are the problem. It is effective at slowing progression of AMD, but not so effective at returning sight. You shouldn’t go without it unless it’s really necessary.

Avastin is injected directly into the eye, and while some will enter the blood, the amount injected into the eye is approximately 0.1% of the amount that would be injected into the blood to treat colon cancer, for example.

BCG (Bacille CalmetteGuerin) is a vaccine strain of bacteria (commonly given to prevent tuberculosis) used to enhance the immune system in people with bladder cancer. BCG treatment of superficial bladder cancer is about 70% effective at giving a complete response. It is instilled directly into the bladder. Since BCG works locally, and not through stimulating blood vessels, I don’t think BCG would be any danger to your eyes.

Since Avastin works via a completely different method from BCG, and because its dose to the bladder is so small, I believe the risk of an adverse drug interaction is much, much smaller than the benefit of each treatment.

Genentech, the maker of Avastin, had no information about interaction between these drugs.

Dear Dr. Roach: I was recently diagnosed with bullous pemphigoid, and the dermatologist recommended 10 mg prednisone. I was hoping you could recommend a different medication.

R.M.

Answer: Bullous pemphigoid is an autoimmune disease of the skin. Prednisone is the first line treatment for people who can’t be treated successfully with steroid creams or ointments. While some experts do use other anti-immune system agents, such as azathioprine, these are usually used in conjunction with prednisone, to allow for lower doses. Your dose of 10 mg is a pretty low dose, so it seems to me to be a very reasonable treatment for many people with bullous pemphigoid.