Monensin's LD50 in lab mice?

Chris Evelo C.Evelo at Farmaco.UniMaas.nl
Tue Feb 10 03:17:49 EST 1998

Octavio Pereira wrote:
> Hello!
> I'm a Veterinary Medicine student, from Lisbon's F.M.V. (Faculty of
> Veterinary Medicine), in Portugal and i'm conducting an essay on the
> toxicity of monensin when given with phenobarbital to lab mice (Mus
> Musculus, Charles River). However i've come to find certain
> contradicting figures relative to the LD50 (lethal dose to 50%) of
> that xenobiotic during the bibliographic research i've made previous
> to start the work. I've found references from 44 mg/kg, oral
> administration, to 144 mg/Kg (quite a difference!!!). In the test it
> is supposed to give the monensin via intraperitoneal, in an emulsion
> of liquid paraffin.
> I've already spent about 30 hours in the WWW trying to retrieve
> something about this and i'm quite frustrated. If anyone could tell me
> where to find accurate data about this subject, he/she would have my
> most profound and everlasting thankfulness!
> For any contact you may reach for me at okarrassa at mail.telepac.pt
> Thanking you all, in advance,
> Octavio Pereira

LD50 values are not physical constants. Differences in reported values
like you describe are quite common. Standardisation of test conditions
(animal strains, houding, climate, food etc.) can improve this somewhat.
The practical consequence is that any LD50 only gives an impression of
acute toxicity. You need not be interested in the exact LD50 for a 
specific mice or rat strain under specific conditions. After all you do
not want to create the savest world for mice, do you?

                    Chris Evelo
 Dr.Ir. Chris T.A. Evelo PhD
 Department of Pharmacology & Toxicology; Universiteit Maastricht
 P.O. Box 616; NL-6200 MD Maastricht; The Netherlands
 tel: +31-43-3881231 +31-43-3881417;  fax: +31-43-3670940
 email: C.Evelo at Farmaco.UniMaas.nl

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