Antiviral

What are they

The family of antiviral drugs includes all those molecules, even very different from each other, which serve to counteract the multiplication of pathogenic viruses within the body, and therefore to treat the infections caused by them.

Mechanism of action

Viruses, unlike bacteria, are not able to reproduce independently: to do so they must enter living cells and exploit their metabolic processes to their advantage.

Different viruses use different mechanisms to enter cells, to multiply inside them, to get out and go to infect other cells and to “circumvent” the defenses that cells put in place when they perceive a foreign presence.

The different types of existing antiviral drugs have been studied precisely to interfere with each of these mechanisms, blocking the multiplication of viruses in the various stages described above.

Therefore, the numerous molecules now on the market are divided into a few large groups based on their respective pharmacological actions.

Classes of drugs

The classes of antivirals grouped according to their functioning are as follows:

• inhibitors of viral envelope disassembly;
• neuraminidase inhibitors;
• inhibitors of fusion between HIV and host cell;
• viral DNA-polymerase inhibitors;
• reverse transcriptase inhibitors (in turn divided into nucleoside compounds and non-nucleoside compounds);
• protease inhibitors.

These complicated definitions become a little clearer if you understand what the processes or molecules that each type of drug inhibits are for:

What are they for?

Viral envelope disassembly inhibitors and neuraminidase inhibitors are predominantly used to fight influenza viruses.

DNA-polymerase inhibitors (the first to be synthesized) are intended for the treatment of infections caused by herpes viruses (cold sores, genital herpes, chickenpox, zoster, herpetic conjunctivitis, mononucleosis), respiratory syncytial virus (early childhood pneumonia), cytomegalovirus (severe fetal infections and in immunosuppressed subjects) and the treatment of hepatitis C.

The last three groups of drugs – HIV-host cell fusion inhibitors, reverse transcriptase inhibitors and protease inhibitors – are mainly intended for the treatment of AIDS virus infection, where they are generally used in combination with each other in the so-called combination therapy, now known by the acronym HAART (Highly Active Anti-Retroviral Therapy).

Some reverse transcriptase inhibitors are also used in the treatment of hepatitis B.

Effects

To produce undesirable effects, often very annoying, are above all the antivirals used in the treatment of HIV infection.

The main ones are:

• gastrointestinal disorders (nausea, abdominal pain, diarrhea);
• skin reactions (erythema, urticaria);
• musculoskeletal symptoms (muscle and joint pain, muscle weakness);
• hematological changes (decrease in red blood cells, white blood cells and platelets);
• metabolic disorders (liver and pancreatic dysfunction, lipodystrophy).

Alternatives

In the fight against viral infections, some compounds have also been included, of natural origin or analogous to those of natural origin, which have the function of reproducing or modulating the body’s immune response:

• immunoglobulins, natural antibodies capable, if administered immediately after infection, to limit the development of certain infections, such as measles, rubella, viral hepatitis, rabies, poliomyelitis;
• monoclonal antibodies, antibodies specialized in recognizing single viral proteins, used in respiratory syncytial virus infections of children;
• interferons, proteins normally produced by cells but now easily synthesized in the laboratory, used mainly in the treatment of hepatitis B and C.