2 Antivirals
Learn how antiviral medicines target specific viruses and what timing, interaction checks, monitoring, and patient counseling matter across common treatments.
How antivirals target viruses
act on particular steps in viral replication. They treat specific viruses, so one antiviral is not interchangeable with another. They are not substitutes for antibiotics when a bacterial infection is present.
Drug classes and their targets
Different antiviral drugs act on distinct targets:
Oseltamivir inhibits influenza neuraminidase.
Baloxavir inhibits influenza cap-dependent endonuclease.
inhibit viral DNA integration into the host genome.
include drug groups that inhibit HCV protease, NS5A, or NS5B polymerase.
Acyclovir and valacyclovir treat herpes simplex or varicella-zoster infections by inhibiting viral DNA replication.
Influenza treatment timing and safety
For people at increased risk of influenza complications, prompt antiviral treatment is recommended. Benefit is greatest when treatment begins early, usually within hours. Do not delay treatment for eligible patients while waiting for test confirmation.
Inhaled zanamivir can cause bronchospasm and is not recommended for people with underlying respiratory disease such as asthma. Oseltamivir commonly causes nausea or vomiting. Antibiotics do not treat influenza.
Herpes treatment and transmission
Acyclovir, valacyclovir, and famciclovir can shorten or suppress genital herpes symptoms and reduce recurrences. They do not eradicate , and transmission can still occur, including when symptoms are absent. Counseling about reducing transmission remains important.
Antivirals are also used to treat shingles, and early treatment is encouraged.
COVID-19 treatment checks
Before starting nirmatrelvir–ritonavir, review all prescription medicines, over-the-counter drugs, and supplements for interactions. Ritonavir strongly inhibits and can substantially change levels of interacting medicines.
Kidney function can affect dosing and eligibility. Treatment must begin within the recommended window, so prompt clinical assessment matters.
HIV therapy, adherence, and monitoring
HIV treatment suppresses viral replication but does not eliminate HIV, so ongoing therapy is needed to maintain suppression. Encourage taking the regimen as prescribed and discussing barriers or adverse effects with the care team rather than stopping or changing medicines independently. Incomplete adherence can contribute to resistance.
is used to assess virologic response, while CD4 testing helps assess immune status. Check for interactions, including with supplements containing calcium, iron, magnesium, or aluminum; these can reduce absorption of some INSTIs.
Hepatitis C treatment considerations
Test for hepatitis B before starting HCV DAA treatment because can occur during or after treatment. Patients with evidence of HBV infection may need monitoring and, in some cases, HBV treatment.
Modern DAA regimens can cure most HCV infections, but the specific regimen and follow-up are determined clinically.