Which drug is primarily used to treat herpes infections?

Acyclovir is primarily used to treat herpes infections due to its mechanism of action as an antiviral medication. It works by inhibiting the replication of the herpes virus, thereby reducing the severity and duration of outbreaks. When the body is infected with the herpes simplex virus, acyclovir gets converted into its active form and selectively targets the virus-infected cells. This selectivity minimizes damage to healthy cells and helps manage symptoms effectively.

The other options do not serve this purpose: Amoxicillin is an antibiotic used to treat bacterial infections, not viral ones; Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) used to relieve pain and reduce inflammation, but it does not have antiviral properties; and Metronidazole is an antibiotic effective against certain bacterial and parasitic infections but is not used for viral infections like herpes. Thus, acyclovir stands out as the appropriate choice for the treatment of herpes infections.