What is the basis for selecting the minimal dose of plant extract for calculating lethal dose for an animal. Many cite previous literature to be the reason for choosing a specific dose, but is there any systemic method or is it just random?
Acute toxicity (LD50) study
Acute toxicity study was carried out using the method
of (Lorke, 1983). In the first phase, nine rats randomly
divided into three groups of three rats per group were
given 10, 100 and 1000 mg extract/kg body weight orally
(via a cannula), respectively. The rats were observed for
signs of adverse effects and death for 24 h and then
weighed daily for 14 days. In the second phase of the
study, the procedure was repeated using three rats
randomly divided into three groups of one rat each, given
1600, 2900 and 5000 mg extract/kg body weight,
respectively. The rats were also observed for signs of
toxicity, mortality and
weighed for 14 days
(Tijani et al., 1986)
Acute toxicity (LD50) study
Acute toxicity study was carried out using the method
of (Lorke, 1983). In the first phase, nine rats randomly
divided into three groups of three rats per group were
given 10, 100 and 1000 mg extract/kg body weight orally
(via a cannula), respectively. The rats were observed for
signs of adverse effects and death for 24 h and then
weighed daily for 14 days. In the second phase of the
study, the procedure was repeated using three rats
randomly divided into three groups of one rat each, given
1600, 2900 and 5000 mg extract/kg body weight,
respectively. The rats were also observed for signs of
toxicity, mortality and
weighed for 14 days
(Tijani et al., 1986)
I would suggest Satyabrata Maiti answer when working on LD50. This is because, plant based compounds work differently and test animal respond in diverse ways. It becomes like a trial experiment until a suitable figure is obtained. Again, the figure might not be the same and will slightly vary when the experiment is repeated.
In the study carried out by our biotechnology research group, animals in ten replicates(of about the same weight) were fed the plant extract by intubation. Control experimental animals were not given any plant extracts. The dosages of the plant extracts were doubled for instance 2mg, 4mg,8 mg 16 mg etc. The dosage that killed 50% of the experimental animals within 24 h was taken as the LD50 value
True! you can employ the suggestion posted by Satyabrata Maiti. However you will need to consider the body weight of the test animals before you can arbitrarily assign the dose levels. The method described by Lorke (1983) will give a great deal of ideas.
The simplest method is...Prepare a range of doses of your plant extract...Assign on group to each dose,,take 8-10 mice in each group...Administer extract to each group.. Observe mortality for 24 hours..the lowest dose at which 50% (4-5) mice will be killed in its particular group will be considered as LD50......you can find many references by using key word acute toxicity assay
The tenant method is straight forward but how do we now calculate the ld50
Hi...
Please follow the link.. these guidelines descirbe how the lethal dose is determined for animal studies..
http://iccvam.niehs.nih.gov/SuppDocs/FedDocs/OECD/OECDtg425.pdf
In LD50 studies are the animals to be fasted before administration of the crude extract ?
it is recommended that the animals be fasted at least between 4- 6 hours or an overnight fast. thanks for the responses
LD50 is calculated as the geometric mean of the highest non lethal dose and the least toxic dose using lorke's method.
Calculation of Median Lethal Dose (LD50)
For each mouse, the observation was made for 24 hr and symptoms of toxicity and rate of mortality in each
group were noted. At the end of study period, expired animals were counted for the calculation of LD50. The arithmetic method of Karber [*] was used for the determination of LD50.
LD50 = LD100 −Σ(a × b) n
n = total number of animal in a group.
a = the difference between two successive doses of administered extract/substance.
b = the average number of dead animals in two successive doses.
LD100 = Lethal dose causing the 100% death of all test animals.
*:Karber, G. (1931) Beitrag zur kollecktiven Behandlung pharmakologischer Reihenversuche. Arch. Exptl. Pathol. Pharmakol, 162, 480-483.
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