Risk for Resistant Viruses. As with antibiotics, doctors are concerned about signs of increasing viral resistance to acyclovir and similar drugs, particularly in immunocompromised patients (such as those with AIDS). Some experts believe, however, that the prevalence of drug-resistant viruses will be low for many years. They argue that widespread use of antiviral drugs will prevent many cases of herpes from developing and will slow the spread of the disease. Even patients on long-term suppressive drug therapy show few signs of drug resistance. In addition, research indicates that many people infected with strains that appear to be drug-resistant in laboratory tests still respond to these drugs.
Foscarnet
Foscarnet (Foscavir) is a powerful anti-viral drug known as a pyrophosphate analogue, and is the first choice for treatment for HSV strains that have become resistant to acyclovir and similar drugs. Administered intravenously, the drug can have toxic effects, including impaired kidney function (which is reversible) and seizures. Fever, nausea, and vomiting are common side effects. It can also cause ulcers on genital organs. As with other drugs, it does not cure herpes.
Cidofovir
Cidofovir (Vistide) is active against many viruses and may be useful in some cases of HSV. Intravenous cidofovir, for example, may be a good choice for patients with HIV/AIDS or bone marrow transplant recipients whose condition is resistant to acyclovir and foscarnet. Cidofovir shows promise as a topical treatment of recurrent genital herpes infections, although it can have severe side effects, including kidney damage.
Investigational Drugs for Herpes
Helicase-Primase Inhibitors. A new class of drugs, called helicase-primase inhibitors, suppress an enzyme vital for HSV replication and growth. They have shown early promise in animal studies, but it will be some years before they are tested for safety and effectiveness in people.
Vaccines. Some experts believe that developing an effective HSV vaccine is the only practical way to control the disease and the spread of infection. Furthermore, if such a vaccine becomes available, then universal immunization may be the best approach. Vaccines also hold the potential for eliminating latent, lifelong infections.
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