Oseltamivir

BRAND NAME: TAMIFLU

AVAILABLE IN    
75 mg CAPSULES  
or                
ORAL SUSPENSION

BACKGROUND

What a miracle the development of antibiotics truly was! The commercial development of penicillin and the sulfa antibiotic class represented the first readily available medications that could kill the microorganisms responsible for bacterial infections. Since then, a myriad of antibiotics have become available exploiting the biological differences between bacterial and animal enzyme systems and cellular structures. But none of these medications made any difference to the viruses.

cpvsmall

This is the actual canine parvovirus
image by JY Sgro, UW-Madison

A virus is the simplest organism that can technically be called “living.” Its structure is very simple, often just a cluster of DNA inside a protein coat. The virus has no protein metabolism or other systems that a medication might target. A virus simply acts like a syringe attaching to a host cell, injecting its genetic material inside, and tricking the host cell into transcribing this material. In other words, it injects its own DNA into the host cell, attaching its own DNA to the host's DNA. The viral DNA instructs the cell to stop what it is doing and start mass-producing more virus. Soon the host cell becomes a virus factory, replicating thousands of new viral organisms to go forward and infect new cells.

Viruses are responsible for Herpes, Influenza, HIV, the Common Cold and numerous other infections with which we are familiar. It has only been relatively recently that we have had the technology to attack viral biology. Oseltamivir represents such an effort.

Oseltamivir specifically targets the influenza virus. This virus bears a special attachment enzyme on its surface called “Neuraminidase.” This enzyme allows the flu virus to bud from the host cell in which it was created and then happily pass through the mucus of the respiratory tract to any cell in the tract it wishes to infect. Inhibiting neuraminidase effectively locks the new viral organisms within their host cell, imprisoning them so that they cannot infect new cells. The immune system will recognize the infected cell and kill it along with its infective contents. Oseltamivir is felt to cut a couple of days out of one’s sickness period when it comes to the flu.

All this, of course, has virtually nothing to do with pets.

Recently, veterinary interest has turned to oseltamivir in the treatment of Canine Parvovirus, a life-threatening infection characterized by vomiting and bloody diarrhea. Because the parvovirus does not use neuraminidase in its replication, one might not expect oseltamavir to have value but it turns out that neuraminidase is an important enzyme used by pathogenic bacteria invading through the protective mucous barrier of the GI tract. Invasion of intestinal bacteria into the bloodstream is an important cause of death in parvoviral infection and this is where oseltamavir appears to be helpful though there is still controversy surrounding its use.

HOW THIS MEDICATION IS USED

To assist in the treatment of canine parvovirus infection, oseltamivir is given orally twice a day for 5 days. The medication should be obtained as soon as the parvovirus diagnosis is confirmed. If a puppy has been exposed to canine parvovirus but is not ill often the clinical disease can be circumvented by giving a course of oseltamivir.

Usually an oral suspension is compounded or the human product is given. This medication is not approved for use in animals.

SIDE EFFECTS

In pets, side effects have not been appreciated; however, veterinary experience is limited but the following is taken from human patient information sheets on oseltamivir:

Side effects that you should report to your prescriber or healthcare professional as soon as possible:

  • difficulty breathing or shortness of breath
     
  • ear ache or infection
     
  • infection and inflammation of the sinuses (nose) and chest
     
  • skin rash

Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):

  • coughing
     
  • diarrhea
     
  • difficulty sleeping
     
  • dizziness
     
  • headache
     
  • nausea and vomiting
     
  • nose bleed

We include this information as general information but if you are using oseltamivir on a pet and think you may be seeing indications of any of the above, report them to your veterinarian.

INTERACTIONS WITH OTHER DRUGS

There are no known drug interactions with oseltamivir.

CONCERNS AND CAUTIONS

The most important caution is to recognize that canine parvovirus is a life-threatening infection for which there is no substitute for hospitalization. One should never attempt to diagnose parvovirus infection on one's own nor treat it without veterinary supervision. Puppies that have advanced parvo symptoms (such as septicemia or severe dehydration) may not respond to oseltamivir. This medication works best early in the course of infection before the patient is already combating large amounts of infectious organisms. If pathogenic bacteria have already invaded, the effectiveness of oseltamavir will be blunted..

Reconstituted oseltamivir does not last longer than 10 days and must be disposed of thereafter.

If a patient seems to have an upset stomach on oseltamivir, this effect can be mitigated by giving the medication with food.

There has been some interest in using oseltamivir in infections other than parvovirus such as Canine Influenza, Canine Distemper, or even Kennel Cough. It is important to consider that human influenza is a significant disease with potential to cause human death under certain circumstances. Unnecessary use of anti-viral medications leads to resistance within the influenza virus population so it is important that medications such as oseltamivir not be used for infections which are not life-threatening in nature or which are likely to resolve with routine supportive care.

For more details on canine parvovirus, see the Parvovirus Information Center on this site.

Page last updated: 12/10/2013