antiviral drug
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What is an antiviral drug?
An antiviral drug is a medication used to treat infections caused by viruses, such as HIV/AIDS, influenza, herpes simplex, viral hepatitis, encephalitis, infectious mononucleosis, and the common cold.
Since viruses rely on host cells to replicate, antiviral drugs inhibit viruses by acting at one of the five basic steps in the viral replication cycle:
1. attachment and penetration of the virus into the host cell
2. uncoating of the virus
3. synthesis of new viral components
4. assembly of the components into new virus
5. release of the virus from the host cell4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do antiviral drugs work in the body?
Antiviral drugs target different stages of the viral replication cycle within the host cell. These drugs inhibit viruses by acting on:
* Attachment and penetration into the host cell
* Uncoating of the virus
* Synthesis of new viral components
* Assembly of components into new viruses
* Release of the virus from the host cellFor example, HIV drugs include reverse transcriptase (RT) inhibitors, which block the action of reverse transcriptase, and protease inhibitors, which prevent the spread of HIV to uninfected cells by blocking viral enzymes.
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What kinds of viruses can antiviral drugs treat?
Antiviral drugs target various viruses, including HIV, influenza A and B, and herpes simplex.
Classes of antiviral medications:
* Reverse transcriptase (RT) inhibitors: Block reverse transcriptase, an enzyme that converts viral RNA into DNA.
* Protease inhibitors: Prevent HIV from infecting healthy cells.
* Fusion inhibitors: Prevent HIV from entering human cells.
* Neuraminidase inhibitors: Reduce the release of the virus from infected cells, the formation of viral aggregates, and the spread of the virus throughout the body.
* Amantadine and rimantadine: Prevent the release of viral RNA into the host cell by blocking the uncoating of the virus within the cell.
* Interferons: Inhibit virus multiplication.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How are antiviral drugs different from antibiotics?
Antiviral drugs and antibiotics differ significantly in their targets and mechanisms. Antiviral drugs treat viral infections like HIV/AIDS and influenza, whereas antibiotics combat bacterial infections.
Viruses consist of either DNA or RNA and a protein coat and must enter a host cell to replicate. Antiviral drugs inhibit viruses by acting at one of five basic steps in the viral replication cycle.
Antibiotics work through various mechanisms, including inhibiting bacterial cell wall synthesis or protein synthesis, ultimately leading to the bacterium's death.
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What are some common side effects or risks of antiviral drugs?
Common side effects of antiviral drugs vary depending on the specific medication and the individual patient.
For example, common side effects of remdesivir, an antiviral drug used to treat COVID-19, include nausea and infusion-related reactions like pain and swelling at the injection site. Remdesivir can also cause elevated liver enzymes, potentially leading to jaundice in rare cases, and may affect kidney function.
Anti-HIV drugs, such as protease inhibitors, may cause nausea and diarrhea, with long-term use potentially leading to lipodystrophy (fat redistribution, hyperlipidemia, and insulin resistance). Fusion inhibitors, another class of anti-HIV drugs, can cause allergic reactions and infections at injection sites.
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Why can viruses sometimes become resistant to antiviral drugs, and how is this problem managed?
Viruses can develop resistance to antiviral drugs due to mutations that allow them to withstand the drug's effects. The drug eliminates non-resistant microbes, enabling the resistant mutants to multiply and create a resistant strain.
To manage this issue, combination treatments like HAART, which combines three or four reverse transcriptase and protease inhibitors, are utilized. If resistance develops, resistance testing determines which drugs are ineffective, allowing healthcare providers to tailor a new salvage regimen for the patient.
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antiviral drug, any agent that is used in the treatment of an infectious disease caused by a virus. Viruses are responsible for illnesses such as HIV/AIDS, influenza, herpes simplex type I (cold sores of the mouth) and type II (genital herpes), herpes zoster (shingles), viral hepatitis, encephalitis, infectious mononucleosis, and the common cold.
Viruses and host cells
Viruses consist of nucleic acid (either DNA or RNA) and a protein coat. Because viruses do not have the enzymes that are needed to manufacture cellular components, they are obligate parasites, which means they must enter a cell for replication to occur. The nucleic acid of the virus instructs the host cell to produce viral components, which leads to an infectious virus. In some cases, as in herpes infections, the viral nucleic acid may remain in the host cell without causing replication of the virus and damage to the host (viral latency). In other cases, the production of virus by the host cell may cause the death of the cell. A major problem in treating some viral diseases is that latent viruses can become activated.
Many factors account for the difficulty in developing antiviral agents. The structure of each virus differs, and specific therapy is often unsuccessful because of periodic changes in the antigenic proteins of the virus (antigenic proteins provoke an immune response in the host). The need for a host cell to support the multiplication of the virus makes treatment difficult because the agent must be able to inhibit the virus without seriously affecting the host cells.
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An antiviral agent must act at one of five basic steps in the viral replication cycle in order to inhibit the virus: (1) attachment and penetration of the virus into the host cell, (2) uncoating of virus (e.g., removal of the protein surface and release of the viral DNA or RNA), (3) synthesis of new viral components by the host cell as directed by the virus DNA, (4) assembly of the components into new virus, and (5) release of the virus from the host cell.
The role of viruses in vaccination
The greatest success against virus infections has been by increasing immunity through vaccination (in the prevention of influenza, polio, measles, mumps, and smallpox) with live attenuated (weakened) or killed viruses. For example, vaccination led to the eradication of smallpox. In the case of influenza, the causative viruses are constantly changing their antigenic proteins; thus, revaccination is required as the antigenic makeup of the viruses changes annually. Some virus groups contain 50 or more different viruses, making effective vaccination difficult.
Passive immunization with serum or globulin (antibodies) from immune persons has been used to prevent viral infections. Immunoglobulins, such as those used against hepatitis and respiratory syncytial virus, are effective only for prevention, not for treatment.
Select groups of antiviral drugs
Antiherpesvirus drugs
Herpesvirus is the DNA-containing virus that causes such diseases as genital herpes, chickenpox, retinitis, and infectious mononucleosis. After the viral particle attaches to the cell membrane and uncoats, the viral DNA is transferred to the nucleus and transcribed into viral mRNA for the viral proteins. Drugs that are effective against herpesviruses interfere with DNA replication. The nucleoside analogs (acyclovir and ganciclovir) actually mimic the normal nucleoside and block the viral DNA polymerase enzyme, which is important in the formation of DNA. All the nucleoside analogs must be activated by addition of a phosphate group before they have antiviral activity. Some of the agents (acyclovir) are activated by a viral enzyme, so they are specific for the cells that contain viral particles. Other agents (idoxuridine) are activated by cellular enzymes, so these have less specificity. Non-nucleoside inhibitors of herpesvirus replication include foscarnet, which directly inhibits the viral DNA polymerase and thus blocks formation of new viral DNA.
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Anti-influenza drugs
Influenza is caused by two groups of RNA-containing viruses, influenza A and influenza B. When the RNA is released into the cell, it is directly replicated and also is used to make protein to form new viral particles. Amantadine and rimantadine are oral drugs that can be used for the prevention and treatment of influenza A, but they have no effect against influenza B viruses. The action of amantadine is to block uncoating of the virus within the cell and thus prevent the release of viral RNA into the host cell. Zanamivir, peramivir, and oseltamivir are active against both influenza A and influenza B. Zanamivir is given by inhalation only, peramivir is given intravenously, and oseltamivir can be given orally. These drugs are inhibitors of neuraminidase, a glycoprotein on the surface of the influenza virus. Inhibition of neuraminidase activity decreases the release of virus from infected cells, increases the formation of viral aggregates, and decreases the spread of the virus through the body. If taken within 30 hours of the onset of influenza, both drugs can shorten the duration of the illness.