Apr 7, 1997
How goes state-of-the-art CMV retinitis treatment? How long can the CMV-afflicted plan to see, and the CMV-blinded hope to live? Thanks.
| Response from Dr. Cohen
There's probably more news in the CMV field than with any other opportunistic infection. First, there are the mainstays of therapy: IV ganciclovir (Cytovene) and IV foscarnet (Foscavir). Both effective, both a bit of a pain in the neck. Ganciclovir causes low white blood cell counts and anemia, and foscarnet, in addition to requiring long infusion times, can cause kidney damage and a host of metabolic disturbances that force you to take numerous supplements in addition to the drug itself. Of course, they both require a permanent catheter, which can become infected or get "clogged up" with a clot. Still, despite their problems, these drugs continue to play a major role in CMV treatment, and are sometimes combined in particularly difficult cases.
What's new? First, there's oral ganciclovir. Its main advantage is that it's oral. It's not quite as effective as IV ganciclovir, still causes the same bone marrow toxicity, is taken at a dose of 4 capsules three times a day, and believe it or not it can be more expensive than the IV form. It's main use is for maintenance:
preventing CMV disease in the opposite eye or the rest of the body in patients who have an intraocular implant, preventing progression of disease in patients with very mild retinitis that is not threatening the central parts of the retina, or preventing relapse of gastrointestinal disease that's been treated successfully. It's also approved for prophylaxis of CMV retinitis, though that will probably become more common when we figure out who's most likely to develop CMV disease, perhaps by using things like CMV antigen tests or CMV viral load tests.
Then there's the intraocular implant (Vitrasert), a device which contains about 6-8 months of sustained release ganciclovir and which is implanted in the eye through an outpatient surgical procedure. The good news: it's probably the most effective way to treat CMV retinitis and to prevent relapse. As long as the device contains the drug, you probably won't relapse. The disadgantages: it won't protect your other eye or the rest of your body, you'll have blurry vision for a few days or weeks after the surgery, there's a significant risk of retinal detachemnt after the surgery, and it's expensive (but then all CMV treatment is expensive).
Finally, we have cidofovir (Vistide), a nucleotide analog with a long duration of action. The advantages: it works well, and you only need to take it once a week during the initial treatment, and once every two weeks after that, so you won't need a permanent catheter. The disadvantages: it can damage the kidneys. In order to prevent kidney damage, you have to take probenecid, which causes allergic reactions or other side effects in a fairly large proportion of people.
There are other things being developed--stay tuned.
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