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Active ingredient: Ribavirin - Brands, Medical Use, Clinical Data

Brands, Medical Use, Clinical Data

Drug Category

  • Antiviral Agents

Dosage Forms

  • Inhalation solution
  • Tablet (oral)

Brands / Synonyms

Biopolymers; Copegus; RBV; Rebetol; Rebetol Intron A; Rebetron; Rebretron; Ribamide; Ribamidil; Ribamidyl; Ribasphere; RIBAV; Ribavirin; Ribavirin Capsules; Ribavirin Triphosphate; Ribavirin [Usan:Inn]; Ribavirin-TP; Ribavirina [Inn-Spanish]; Ribavirine; Ribavirine [Inn-French]; Ribavirinum [Inn-Latin]; RTC; RTCA; RTP; Tribavirin; Varazid; Vilona; Viramid; Virazid; Virazole; Virazole 5'-triphosphate

Indications

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.

Mechanism of Action

Ribavirin is readily phosphorylated intracellularly by adenosine kinase to ribavirin mono-, di-, and triphosphate metabolites. Ribavirin triphosphate (RTP) is a potent competitive inhibitor of inosine monophosphate (IMP) dehydrogenase, viral RNA polymerase and messenger RNA (mRNA) guanylyltransferase (viral). Guanylyltranserase inhibition stops the capping of mRNA. These diverse effects result in a marked reduction of intracellular guanosine triphosphate (GTP) pools and inhibition of viral RNA and protein synthesis. Ribavirin is also incorporated into the viral genome causing lethal mutagenesis and a subsequent decrease in specific viral infectivity.

Absorption

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

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).

Biotrnasformation / Drug Metabolism

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.

Contraindications

COPEGUS (ribavirin) is contraindicated in:

· Patients with known hypersensitivity to COPEGUS or to any component of the tablet.

· Women who are pregnant.

· Men whose female partners are pregnant.

· Patients with hemoglobinopathies (e.g., thalassemia major or sickle-cell anemia).

COPEGUS and PEGASYS combination therapy is contraindicated in patients with:

·Autoimmune hepatitis.

·Hepatic decompensation (Child-Pugh score greater than 6; class B and C) in cirrhotic CHC monoinfected patients before or during treatment

·Hepatic decompensation with Child-Pugh score greater than or equal to 6 in cirrhotic CHC patients coinfected with HIV before or during treatment

Drug Interactions

Clinical studies of interactions of VIRAZOLE with other drugs commonly used to treat infants with RSV infections, such as digoxin, bronchodilators, other antiviral agents, antibiotics, or anti-metabolites have not been conducted. Interference by VIRAZOLE with laboratory tests has not been evaluated.

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