Used primarily as an antiviral agent, especially in the treatment of cytomegalovirus (CMV) infections in immunocompromised patients, such as those with AIDS. It is effective in managing CMV retinitis when other treatments are not suitable. Also shows activity against a range of DNA viruses, including herpesviruses, adenoviruses, and poxviruses. Investigated for use in treating infections caused by drug-resistant viruses and has been used off-label in cases of severe adenovirus or BK virus infections in transplant recipients. Topical formulations have been applied in the treatment of recalcitrant warts caused by human papillomavirus (HPV). Its long intracellular half-life allows for infrequent dosing, though nephrotoxicity limits its use and requires careful monitoring.