The antiviral medications used include acyclovir, penciclovir, valacyclovir, and famciclovir. Antiviral medications, such as acyclovir, valacyclovir, may prevent outbreaks or shorten outbreaks if they occur. Treatment is usually with antivirals such as acyclovir or valacyclovir by mouth. Antivirals such as acyclovir, famciclovir, or valacyclovir may be used. To treat the herpes simplex virus, IV acyclovir is administered for 21 days. Treatment is generally with antiviral pills such as acyclovir. Antiviral medications, including acyclovir, are effective at controlling viral reactivation. Another study found that ribavirin potentiated the antiviral effect of acyclovir. Antiviral prophylaxis such as daily acyclovir in immunocompromised individuals may be considered. The primary exception to this is herpes simplex encephalitis, which is treatable with acyclovir. Treatment may include antiviral medications (such as acyclovir), anticonvulsants, and corticosteroids. Several antiviral drugs are effective for treating herpes, including aciclovir (acyclovir), valaciclovir, famciclovir, and penciclovir. Topical acyclovir has not been shown to be effective in management of herpetic whitlow. It has a longer duration of action than acyclovir and it only comes in tablets. Valacyclovir is a prodrug that is converted to acyclovir once in the body.