Category Archives: Medicines & Treatments

Chemotherapy And Cytotoxic Drugs

What is chemotherapy?

Cancer chemotherapy uses cytotoxic drugs to kill cancer cells. Unfortunately they also affects normal rapidly multiplying cells like those that line the gut and bone marrow cells that produce blood cells.

What is cancer?

Cancer is a disease of uncontrolled growth of cells. Cells are the basic structural units of the body. Normally they replicate to replace themselves as they age. In cancer a particular cell line multiplies in an inappropriate and uncontrolled manner.

What are cytotoxic drugs?

Many anti-cancer drugs are cytotoxic. Cytotoxic means “damaging to cells”. These drugs block cell growth and division and thus prevent cancer cells from multiplying. Cytotoxic drugs act only on rapidly dividing cells such as cancer cells but they can also harm normal body cells.

What side effects do cytotoxic drugs have?

Because cytotoxic drugs affect all rapidly dividing cells in the body, normal cells in blood-producing bone marrow, the gut, skin and reproductive organs are also affected.

Many animals on chemotherapy experience no side effects. However, they are more prone to infections, bleeding, vomiting, diarrhoea and loss of appetite.

Animals do not lose all their fur with chemotherapy drugs. Reproductive function is usually not relevant.

Some cytotoxic drugs cause liver, kidney or heart problems. The most serious side effect of chemotherapy is infection. We monitor for these problems with regular blood tests.

Am I at risk of exposure from these drugs?

Cytotoxic drugs are very potent and must be handled with care. We admit animals to hospital to administer most chemotherapy. Some are given by injection while other drugs are given as capsules or tablets.

Do not to handle urine or faeces after any chemotherapy session.

This information is of a general nature only, and must not be used as veterinary advice except where directed by your veterinarian. Hall Veterinary Surgery does not warrant the suitability of this information for specific cases. If your animal is unwell or you want to act on this information, please contact us on 6230 2223.

Follow up on APVMA review of adverse reactions in veterinary products.

The alarming tone of Rosslyn Beeby’s front page article in the Canberra Times 29th December, sent me to the source of her information and statistics, the Australian Pesticide and Veterinary Medicines Authority’s 2009 review of adverse reactions.

The Canberra Times claims were highly inflated. Beeby says:

“According to a report published last week by the Australian Pesticides and Veterinary Medicines Authority (APVMA), the deaths of more than 60 dogs in 2009 were associated with commonly used veterinary chemicals and vaccines.”

I found one canine death as a result of the use of imidacloprid (Advantage, Advantix, Advocate) and one from moxidectin microspheres (Proheart SR12). Consistent counts of around ten deaths for each component of a C5 vaccine, lead me to believe that around ten to fifteen deaths occurred due to C3 and C5 vaccinations (by far the most common). I am at a loss to find the other deaths reported in the Canberra Times.

Reported feline deaths due to vaccines are as low as 2-6. Again, most feline vaccinations are polyvalent, and so are over reported.

In all of the major vaccination adverse reaction reports, canine and feline, the APVMA added:

Due to the low number of reports when taking into consideration the large number of dogs (or cats) vaccinated each year, no further regulatory action is required other than continuing monitoring for future adverse effects.

Parvovirus infection is rife in the puppy population at the moment and many are dying of it. Distemper, hepatitis and parvovirus are often fatal, even with intensive treatment, and always painful and debilitating.

Australia wide usage of vaccines in 2009 is probably one to two million doses. Hall Veterinary Surgery alone gave more than 1000 canine vaccinations in 2009. Compared to the adverse reaction death rate, the death rate of dogs contracting hepatitis, distemper or parvovirus is very high. The benefits of vaccination far outweigh the risks.

Hall Veterinary Surgery recommends triennial immunisation with the core vaccines for distemper, hepatitis and parvovirus in dogs, and an annual vaccination for cats. One of the components of the cat vaccination, the herpesvirus, doesn’t guarantee three years of immunity. Dogs visiting boarding kennels or in constant contact with other dogs at dog parks, obedience trials, on walks etc require annual kennel cough boosters. Feel free to discuss all these aspects with your vet at your pet’s next annual check up.

There were no reported deaths in either cats or dogs with the use of fipronil, one with moxidectin (Proheart Sr12) and one with imidacloprid. The APVMA concluded that:

Given the very high sales volume, the incidence of adverse reactions is low. Therefore no regulatory action is required …( for imidacloprid) and

Due to the low number of reports when taking into consideration the large number of dogs treated each year, no further regulatory action is required.. (for moxidectin)

The Canberra Times article went on:

Several over-the-counter flea sprays and spot-on treatments contain chemicals that have been banned in Europe for more than a decade

The author didn’t say where she found this information, but it would appear the APVMA hasn’t banned them here because they are considered safe enough if used correctly. Veterinary advice is important even for over the counter products. We see deaths due to paralysis tick toxicity regularly and flea infestations are uncomfortable and unhealthy.

The Canberra Times goes on:

In one instance cited in the APVMA report, a flea treatment containing the insecticide imidacloprid prompted 255 reports of ”adverse reactions” in dogs, ranging from nerve inflammation, skin irritations, vomiting, seizures and difficulty in walking. The chemical was banned in France more than a decade ago after it was linked to the death of billions of bees.

Imidacloprid was withdrawn as a sunflower seed treatment in France in 1999. There is still scientific debate as to whether this withdrawal was justified or not.

The Canberra Times also reports:

The report reveals another commonly available flea treatment containing the insecticide fipronil was linked last year to 42 reports of adverse reactions in dogs, and 38 in cats. Fipronil is banned in France, Uruguay and China, but the chemical is widely used in Australia to control fleas, ticks, cockroaches, ant infestations and crop pests including locusts.

Fipronil is subject to review but the APVMA reports no deaths with the use of this insecticide and the low probability that fipronil itself causes adverse reactions. Sometimes the carrying agent of insecticides causes skin reactions.

Permethrin is toxic to cats and is should only be used in cat-free households.

Ask at the Hall Veterinary Surgery for instructions on how to safely apply these products.

The Canberra Times article has left us scratching our heads. Our reading of the APVMA report left us in agreement with the APVMA that the incidence of adverse reactions – and fatalities in particular – was relatively low in all the products mentioned. Whilst all of the products contain a risk in their usage, the benefit when the products are used as recommended far outweighs the risk.

Please discuss any concerns that you have with your vet. All of our vets are keeping up to date with developments within the industry, trying to find safer products and protocols for your pet.

Cortisone

Cortisone

We often prescribe cortisone for allergies and immune related diseases. Prednisolone, Macrolone or Antihistalone tablets contain a form of cortisone called prednisolone.  Short or long acting cortisone injections contain dexamethasone.

After 5 days of prednisolone tabs every day the adrenal glands start to slow their production of natural cortisol. It is safe to stop after 5 days of daily tablets but if we prescribe a longer course follow our instructions carefully.  Usually we recommend every other day tablets so that the adrenal glands keep functioning.

On a long course of prednisolone do not stop giving the tablets suddenly. Your pet may not be able to step up the production of cortisol fast enough to cope with an emergency, like a dog attack, a new pet or illness, and may collapse.

Side effects of cortisone include:

  • Increased fluid intake
  • Increased urine production
  • Increased appetite

Longer term and more serious side effects of cortisone include:

  • Cushings disease signs like a pot belly, flakey skin, enlarged liver and weak legs
  • Diabetes mellitus

Cortisone and anti-inflammatories given at the same time cause stomach ulcers.  We give anti-inflammatories such as Previcox, Deramax, Rimadyl, Metacam and Meloxicam for postoperative pain relief or arthritis. Please make sure your vet knows that your pet is on anti-inflammatories already.

A short acting dexamethasone injection rarely causes more than a mild increase in fluid and food intake.

We only inject long-acting dexamethasone if your pet is difficult to medicate or if your cat has a chronic condition that is not responsive to other cortisones.  Cats are generally more resistant than dogs to the side-effects of cortisone but very occasionally long-acting dexamethasone tips a weak heart into failure.