What is the alternative to acyclovir for treating genital herpes in a patient with an acyclovir allergy?

Alternatives to Acyclovir for Genital Herpes in Patients with Acyclovir Allergy

For patients with acyclovir allergy, valacyclovir and famciclovir are NOT appropriate alternatives as they can cross-react with acyclovir; foscarnet is the recommended treatment option for genital herpes in these patients. 1

First-Line Alternative Treatment

• Foscarnet 40 mg/kg body weight IV every 8 hours is the recommended treatment for patients with acyclovir allergy until clinical resolution is attained 1
• Foscarnet is effective for treatment of genital herpes in patients who cannot take acyclovir or its derivatives 1
• All acyclovir-resistant strains are also resistant to valacyclovir, and most are resistant to famciclovir, making these medications unsuitable alternatives for patients with acyclovir allergy 1

Second-Line Alternative Treatment

• Topical cidofovir gel 1% applied to the lesions once daily for 5 consecutive days may be effective for localized lesions 1
• This option is particularly useful for patients with mild disease who cannot tolerate systemic foscarnet 1

Treatment Considerations Based on Disease Severity

For Mild to Moderate Disease

• Topical cidofovir gel 1% once daily for 5 days 1
• Consider consultation with an expert in infectious diseases for management 1

For Severe Disease

• Intravenous foscarnet 40 mg/kg every 8 hours until clinical resolution 1
• Hospitalization may be required for patients with severe symptoms or complications 1

Important Clinical Considerations

• Allergic reactions to acyclovir, valacyclovir, and famciclovir are infrequent but can occur 1
• Desensitization to acyclovir has been described and may be considered in consultation with an allergy specialist if other options are limited 1
• Patients should be monitored closely for adverse effects of foscarnet, which can include nephrotoxicity and electrolyte abnormalities 1

Special Populations

Immunocompromised Patients

• Immunocompromised patients with acyclovir allergy require close monitoring due to higher risk of severe disease 1
• Higher doses of foscarnet may be required for immunocompromised patients with severe disease 1
• Treatment should continue until complete clinical resolution is achieved 1

Pregnant Patients

• Limited data exists on foscarnet use during pregnancy 1
• Treatment decisions should weigh the potential risks and benefits, with consideration of disease severity 1
• Consultation with maternal-fetal medicine specialists is recommended 1

Patient Education and Follow-up

• Patients should be advised to abstain from sexual activity while lesions are present 1
• Patients should be educated about the natural history of genital herpes, including potential for recurrent episodes 1
• Regular follow-up is essential to assess treatment response and manage potential adverse effects of alternative medications 1

Prevention of Transmission

• Condom use should be encouraged during all sexual exposures 1
• Patients should be advised about the risk of transmission even during asymptomatic periods 1
• Partners should be informed about the infection and potential risks 1