Drug Groups

approved

Description

A nucleoside antimetabolite antiviral agent that blocks nucleic acid synthesis and is used against both RNA and DNA viruses. [PubChem]

Indication

For the treatment of chronic hepatitis C and for respiratory syncytial virus (RSV).

Pharmacology

Ribavirin is an anti-viral drug active against a number of DNA and RNA viruses. It is a member of the nucleoside antimetabolite drugs that interfere with duplication of the viral genetic material. The drug inhibits the activity of the enzyme RNA dependent RNA polymerase, due to it's resemblence to building blocks of the RNA molecules. The oral form is used in the treatment of hepatitis C, in combination with interferon drugs. The aerosol form is used to treat respiratory syncytial virus-related diseases in children. The primary serious adverse effect of ribavirin is hemolytic anemia, which may worsen preexisting cardiac disease.

Toxicity

Side effects include "flu-like" symptoms, such as headache, fatigue, myalgia, and fever. The LD₅₀ in mice is 2 g/kg orally and is associated with hypoactivity and gastrointestinal symptoms (estimated human equivalent dose of 0.17 g/kg, based on body surface area conversion).

Affected Organisms

Biotransformation

Hepatic. Results of in vitro studies using both human and rat liver microsome preparations indicated little or no cytochrome P450 enzyme-mediated metabolism of ribavirin, with minimal potential for P450 enzyme-based drug interactions. Ribavirin has two pathways of metabolism: (1) a reversible phosphorylation pathway in nucleated cells; and (2) a degradative pathway involving deribosylation and amide hydrolysis to yield a triazole carboxylic acid metabolite.

Absorption

Rapidly and extensively absorbed following oral administration. However, due to first-pass metabolism, the absolute bioavailability averages 64%.

Half Life

9.5 hours

Clearance

* Apparent cl=26 L/h [A single oral dose]

References

External Links