Antiviral Agents

Amantadine and rimantadine have what is called an adamantyl cage structure. When the virus is endocytize into the cell, the influenza A membrane protein M2 is responsible for a transmembrane protein transport which increases the acidity inside of the cell and allows encoding. Both the adamantyl cage structure of amantadine and rimantadine interferes with this transmembrane protein hydrogen ion transport and, therefore, there can't be encoding of the virus. So, that is how these agents interfere with the influenza A virus replication. Blockage of the hydrogen ion channel reduces intracellular acidification which is necessary for fusion of the influenza A to the host cell endosomal membranes and release of viral RNA. Influenza B lacks the M2 protein and therefore influenza B is not inhibited by either amantadine or rimantadine.
Indications for amantadine and rimantadine. Prophylaxis of influenza A as well as treatment of influenza A. Now, for treatment of influenza A, efficacy is greatest if the medications are given within 48 hours from the onset of symptoms. Rimantadine does not have FDA indication for treatment in children. However, it is equally efficacious with amantadine. I would have no problems with using rimantadine in children for treatment if I was going to use the medication because it is certainly much safer than amantadine.
The indications for prophylaxis. Immunization with an appropriate influenza vaccine is the prevention method of choice. This method of choice may not be adequate when the circulating strain is not in the vaccine you may want to consider chemoprophylaxis. You may want to give rimantadine or amantadine simultaneously to the vaccine if the vaccine is delayed until the influenza A outbreak has occurred. This is particularly relevant if you have a child who currently now is receiving the vaccine that could lead for the first set of vaccines two doses four weeks apart. If you delayed it until the onset of the epidemic, you may need to do it with the amantadine and rimantadine for actually the entire six weeks because it will take four weeks to get the vaccines in and it takes about two weeks after the second dose to have an adequate immune response. So, if the vaccine was delayed, you can use the chemoprophylaxis.
tions or hospitals, or in home settings in which the child at risk for influenza related complications (children who have bronchopulmonary dysplasia or cystic fibrosis). If you have a child who can't take the vaccine, because they have anaphylaxis to egg protein or their age is less than six months, you may want to prophylax the individuals around that person in order to try to reduce the amount of disease. Another situation where prophylaxis would
Another indication for prophylaxis would be during an outbreak in institu-
tions or hospitals, or in home settings in which the child at risk for influenza related complications (children who have bronchopulmonary dysplasia or cystic fibrosis). If you have a child who can't take the vaccine, because they have anaphylaxis to egg protein or their age is less than six months, you may want to prophylax the individuals around that person in order to try to reduce the amount of disease. Another situation where prophylaxis would
be indicated is if you have a child who comes to your office who has influenza and they happen to have a sibling who is at risk for influenza related complications. It is better to prophylax the family members so that you can protect the at-risk child, because in general, most of the time, influenza is going to be a relatively benign disease for the healthy child and what you are trying to do is prevent disease in the child at risk.
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