Antivirals are drugs, which are used to target and combat numerous viral infections or to provide protection, usually for a short period, against the infection itself. They act by inhibiting one of the various phases of the replication cycle of the virus (absorption and penetration of the virus into the host cell, transcription and translation of the viral genome; assembly and maturation of virions, or complete viral particles). They may have therapeutic and preventive action.
There are different types of antiviral drugs, each of which is specifically designed to combat a particular type of virus:
- Anti-virus influenza drugs: amantadine, can counter the influenza A virus; zanamivir and oseltamivir are active against influenza virus types A and B, including strains resistant to amantadine;
- Anti-virus herpes drugs: acyclovir is the antiviral reference for anti-herpes therapy. It is used both against cold sores and genital herpes (herpes simplex) than against chickenpox and herpes zoster. Then there are valacyclovir, penciclovir and famciclovir that have a spectrum of action similar to aciclovir, but include more side effects. Alternative medications against these viruses can also include idoxuridine and vidarabine (the latter is especially used against Herpes simplex);
- Anti-virus hepatitis drugs: interferon for the treatment of different types of hepatitis and ribavirin, used commonly to treat chronic hepatitis C;
- Drugs for HIV: Highly Active Anti-Retroviral Therapy, or HAART is associated with using more antivirals in the treatment of HIV infection: this association is necessary as monotherapy with this virus easily becomes resistant. Among the antiviral used against HIV are zidovudine or AZT, the fosamprenavir and methisoprinol.
- Drugs against viruses of the Poxviridae family: trifluridine and metisazone (infections caused by poxvirus generally determine the appearance of nodular or pustular skin lesions).
How should antivirals be taken?
The antivirals are commercially available in the form of tablets, capsules or suspensions to be taken orally, or in the form of solutions for injections. There are also creams that allow the topical use of antivirals (useful for example in the case of cold sores).
Antivirals should always be used under prescription and by strictly following your doctor's instructions regarding the dosage and mode of application. Not doing so can reduce the absorption of the drug or render the treatment useless, or in some cases, even stimulate the development of drug resistance.
The duration of treatment varies greatly from case to case: some infections (such as herpes simplex, for example) can take a few days of use, while others (such as herpes zoster) may require continuation of antiviral therapy for 1 to 2 weeks. On the other hand, the HIV virus requires a treatment that lasts for years, the objective of which is – for now – to prevent the viral replication in the body (and not the complete eradication of the infection, which remains chronic) so as to reduce the damage caused to the immune system.
Contraindications and warnings associated with the use of antivirals
Antiviral medications can cause adverse effects, especially the ones used in the treatment of HIV infections. However, in general, the overall adverse effects of antiviral drugs include the following:
- Gastrointestinal disorders: nausea, vomiting, diarrhea, abdominal pain;
- Dermatological disorders: burning, erythema, pain;
- Musculoskeletal disorders: muscle and joint aches, muscle weakness;
- Hematologic alterations: decrease of red blood cells, white blood cells and platelets;
- Metabolic disorders: liver, kidney and pancreas dysfunction;
- Central disorders: headache, confusion, lethargy, tremors, convulsions, coma, hallucinations, agitation, drowsiness, aggressive behavior, ataxia, paresthesia;
In cases of pregnany and nursing, administration of antiviral medications requires careful evaluation of the clinical benefits and potential risks. In general, their use is not recommended.
