Aspirin and Cats.
Abstract:
The claim of the Research Defence Society is that it is a myth that "Aspirin is highly
poisonous to cats". [1] They are wrong, aspirin is highly poisonous to cats.
The same wrong information is also repeated by Kevin O'Donnell in his Animal Rights
Myths FAQ [2]. We use the same source document as the RDS which concludes:
Aspirin should seldom, if ever, be administered to cats because of low efficacy
and potential toxicity [3].
Aspirin and and It's Toxic Effects in Cats
The pro-vivisection group the Research Defence Society and the Secretary of
Seriously Ill For Medical Research (another pro-vivisection group) Kevin O'Donnell
accuse anti-vivisection groups and individuals of spreading myths about vivisection and
differences between humans and animals.
On the subject of aspirin and cats the RDS claims that Dr Robert Sharpe's assertion
that "Aspirin is highly poisonous to cats" is a myth.[1] Whilst in O'Donnell's
Animal Rights Myths he asserts the same thing without naming a source for the myth.[2]
They try to prove their point with the following assertions -
The RDS states: "
Aspirin is not inordinately toxic to cats. There are papers in the veterinary
literature that describe the effects of high doses of aspirin in cats and these
have been taken to represent the effect of doses equivalent to those by patients." [1]
Whilst O'Donnell's states : "In fact, aspirin is only toxic to cats in doses far
higher than those used by humans." [2]
Both the RDS and O'Donnell state : "
For example, 60 mg/kg of aspirin given 5 times in one day produced death
in cats within 36 hours of the first dose." [1][2]
The RDS and O'Donnell both quote their source as [3]. But both the RDS and O'Donnell fails
to grasp the difference between a dose that is poison (or toxic) and a dose that causes death.
Churchill's Medical Dictionary states:
| Toxic Dose |
The amount or intensity of an agent which induces a measurable deleterious
effect on the organism. |
| Lethal Dose |
The amount of a substance that can kill one or more organisms. |
The "myth" says "highly poisonous to cats" and yet they quote a lethal dose and thus
offer no evidence to the contrary.
We looked at the paper the RDS/O'Donnell quote as their source.
The authors state: "The purpose of this investigation was to find a safe, effective analgesic drug for use
in feline practice." [3]
And while the paper does state that 60 mg/kg of aspirin every four hours killed 2 cats
within 32 hours, it is what the paper says about the toxic effects of aspirin in the
cat that is very revealing. The paper opens with it's Summary and Conclusions,
the SECOND line of the paper states :
"Results indicated that aspirin should seldom, if ever, be given to cats because
of its low efficacy and potential toxicity." [3]
The papers Discussion section of page 1166 states:
Our results further confirm the dangers inherent in the extrapolation of information
from one species to another. Salicylate is an unusually stable drug in the cat and
accumulates in the body until toxic levels result. Our findings corroborate previous
reports of toxicity of aspirin in the cat. We feel aspirin should be administered to
cats only under extraordinary circumstances and should not exceed 40 mg/kg every 24 hours.
The practitioner should be alert to the possibility that an owner may administer aspirin
to his sick pet and unwittingly produce salicylate intoxication. One of us (E.J.D.)
has observed 4 such cases in his practice within the past 6 months.[3]
The papers Conclusion states:
Aspirin should seldom, if ever, be administered to cats because of low efficacy
and potential toxicity.[3]
Christiansen [4] states on page 1136:
As with a number of other chemical agents, there seem to be problems with the ability
of the cat to detoxify aspirin. This contributes to the potential toxicity of
aspirin in cats.
... A relatively low dose of 33 mg/kg/day was found to produce partial anorexia and
depression after the first or second dose, and vomiting after the fourth dose.
...cat owners should be educated regarding the dangers associated with the
use of aspirin in the cat.
The safe dose for Aspirin as an analgesic in humans is:
300 mg - 900 mg every 4-6 hours when necessary; max. 4g daily.[5 page 195]
In the same publication on page 435 under the section "Drugs used in rheumatic disease and
gout" the following doses are given for Aspirin: [5]
0.3 - 1g every 4 hours; max. in acute conditions 8g daily; CHILD, juvenile arthritis,
up to 80 mg/kg daily in 5-6 divided doses, increased in acute exacerbation's to 130 mg/kg.
The table below shows the smallest, largest and maximum dose for Aspirin as an analgesic
and then again for rheumatic disease and gout and shows how many times the dose is bigger
than the 33 mg/kg/day dose that causes a toxic reaction in cats, for a 70 kg man.
| |
Dose of Aspirin |
mg/kg/day for a 70kg man |
Times more than 33 mg/kg/day |
| Analgesic |
300mg every 6 hours |
25.7 |
0.8 |
| |
900mg every 4 hours |
51.4 |
1.6 |
| |
4g Maximum Dose |
57.1 |
1.7 |
| Rheumatic |
0.3g every 4 hours |
17.1 |
0.5 |
| |
1g every 4 hours |
17.1 |
1.7 |
| |
8g Maximum Dose |
114.3 |
3.5 |
It should be noted that in the National Formulary the 8g Maximum Dose carries a rider
that the patient should be kept under constant observation on this dose. Having said that
it can be seen that a dose of 33 mg/kg/day is safe for humans but causes:
partial anorexia and depression after the first or second dose [4]
The RDS is wrong when it states:
- Aspirin is not inordinately toxic to cats.
- There are papers in the veterinary literature that describe the effects of
high doses of aspirin in cats and these have been taken to represent the
effect of doses equivalent to those by patients.
- It is a myth that "Aspirin is highly poisonous to cats".
O'Donnell is wrong when he states:
- In fact, aspirin is only toxic to cats in doses far higher
than those used by humans.
- It is a myth that "Aspirin is highly poisonous to cats".
The RDS basically accuses Dr Robert Sharpe of being stupid, a bad researcher and
guilty of spreading myths. Yet how stupid is the person who quotes a paper but gets
almost every single fact quoted from it wrong?
And what of O'Donnell. In his Animal Rights Myths FAQ [2] he states:
This FAQ has been compiled to help aid informed debate on the use
of animals in biomedical research. Debate on the subject on
newsgroups like talk.politics.animals (t.p.a.) and
uk.politics.animals (uk.p.a.) is hampered by the fact that the
same familiar myths about the use of animals in research
continually resurface. Many of these have an urban myth-like
quality and/or are lifted straight from the publications of
animal rights (AR) organisations by newcomers unaware of the real
facts.
It would seem that Mr O'Donnell is describing himself, just substitute
the "animal rights" for "pro-vivisection".
He goes on to state:
This FAQ gives the true stories behind a series of AR
myths, where appropriate citing references to primary sources
which allow readers to check the facts for themselves. The
information collected here shows that AR myths have no more basis
in fact than other urban legends like the 'vanishing hitchhiker'
and 'dead grandmother on the roof-rack' stories.
When we checked the sources we found that on this occasion the real people spreading
"urban myths" were the pro-vivisection groups.
| References |
| 1 |
http://www.uel.ac.uk/research/rds/armyths/sideff/aspirin.html |
| 2
| http://www.cix.co.uk/~embra/armyths.html |
| 3 |
Analgesic drugs in the Cat,
Davis LE and Donnelly EJ,
Journal of American Veterinary Medical Association,
November 1st 1968, Volume 153(9), Page 1161-1167.
|
| 4 |
Veterinary Medicine and Small Animal Clinician,
Gary Christiansen
July 1980, Volume 75, Number 7 is pages 1133 - 1141 including the double page advert for flea repellent.
|
| 5 |
The British National Formulary,
Number 35, March 1998.
|
|