The New Straits Times, March 29, 1999
QUESTION: Recently I read that doctors are experimenting treating patients suspected of having contracted the Hendra-like virus with a drug called ribavirin. Could you please tell me more about this drug?
ANSWER: Ribavirin (rye-ba-vye-rin) belongs to the category of antiviral drug. It is a synthetic nucleoside antiviral agent for oral inhalation therapy. It was originally synthesised in the 1970s and has been shown to be active against many DNA and RNA viruses.
It is used as a primary agent to treat respiratory synctral virus infections and was approved by the United States Food and Drug Administration in December 1985 for use as an aerosol in the treatment of this condition. In January 1994, several foreign countries recognised ribavirin as useful in treating herpes zoster and herpes genitalis infections, as well as varicella.
The FDA approved ribavirin oral capsules in combination with interferon-alpha on June 3 last year for the treatment of chronic hepatitis C in patients with compensated liver disease who have relapses following interferon-alpha therapy. Ribavirin monotherapy is not effective for the treatment of chronic hepatitis C.
It is usually used to treat severe virus pneumonia in infants and young children. Although it may also be used for other virus infections as determined by your doctor, it will not work for certain viruses, such as the common cold.
How ribavirin acts is not fully understood, but its action is intracellular, and the drug appears to selectively inhabit viral DNA and RNA synthesis over cellular (e.g. host cell) DNA and RNA, synthesis in viral-infected cells. The antiviral action of ribavirin appears to require the intracellular phosphorylation to the triphosphate and monophosphate forms.
Ribavirin has some cytotoricity within vital cells but at a much higher concentration than that required to inhibit viral DNA synthesis. Antiviral and cytotoxic effects are reversible following removal of the drug. There also may be an immunologic effect.
The amount of drug absorbed into respiratory tract secretions varies depending on method of delivery, concentration of drug in solution, and length of time of delivery. There is rapid absorption following oral administration, resulting in peak concentrations within 1-2 hours. Most of the drug is excreted in the urine.
Before receiving this medicine a few factors should first be considered. These include the following:
- Allergies -- If you or your child has ever had any unusual or allergic reaction to ribavirin tell this to your doctor. Also mention if you or your child is allergic to any other substances, such as foods, preservatives, or dyes.
- Pregnancy -- Ribavirin is not usually prescribed for teenagers or adults. Although studies have not been done in pregnant human, ribavirin has been shown to cause birth defects and other problems in certain animal studies. Be sure you have discussed this with your doctor.
- Breast-feeding -- Ribavirin is not usually prescribed for teenagers or adults. However, ribavirin passes into the breast milk of animals and has been shown to cause problems in nursing animals and their young.
- Children -- This medicine has been tested in children, and, when used as it should be and in effective doses, has not been shown to cause serious side effects or problems.
- Older adults -- Ribavirin is not usually prescribed for use in elderly patients.
Along with its needed effects, a medicine may cause some unwanted effects. The following side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side-effects continue or are bothersorre: Headache; itching, redness, or swelling of eyes; skin rash or irritation.
Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.
To date there is little overdose experience with this drug. Clinical studies indicate primary symptoms to be increased in bilirubin and anaemia, followed by rebound reticulocytosis.
Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although these uses are not included in product labelling, ribavirin is used in certain patients with the following medical conditions:
- Influenza A and B (given by aerosol inhalation)
- Lassa fever (either given orally or by injection)
Its use for Hendra-like virus is still not yet well-established. However local experts have been quoted as saying that the drug may work for Hendra-like virus. A seven-day regime treatment with the drug is estimated to cost about RM3,000. -- National Poison Centre
