Dear eminent researchers good morning,
I am confused in giving dosage to the rats. initially the experiment animals I grouped based on body weights (180+/- 20 Kg) and prepared the dose as belong. after one week I weighed the rats and found increased body weights about 10 grams. Now, what I will follow either I maintained the same dose up to end of the treatment (one month) or increase the dose according changes in body weights weekly?
Please clarify or suggest me to read any related articles.
Dosage depend on the the type of treatment (medicines). Generally people give in Rat Dosage 1000 mg/kg body wt. You contact to pharmacist for suitable calculations of dosage
doses are generally given on a mg/kg of body weight basis, and generally in 0.1 ml/100 g of body weight (for rats, for mice it's 0.1 ml/10g of body weight). The calculations are pretty easy. An example for delivering 10 mg/kg for a 500 g rat would be:
0.5kg x 10 mg/kg = 5 mg
500 g x 0.1 mg/100 g body weight = 0.5 ml
You want 5 mg delivered in 0.5 ml, so 5 mg/0.5 ml = 10 mg/ml
So for rats a 10 mg/ml solution will deliver 10 mg/kg if you give 0.1 ml/100 g of body weight. From this it's easy to figure things out. Want 5 mg/kg, give X ml of a 5 mg/ml solution, where X is the weight in kg. A 300 g rat would get 0.3 ml, a 256 g rat would get 0.256 ml. Dilute 1:10 and you will have a 0.5 mg/ml solution, and then 0.3 ml in a 300 g rat will be 0.5 mg/kg.
In regards to your specific issue, your rats are constantly growing and gaining weight. That's just normal for them. So you should weigh frequently and adjust dose based on weight. I generally find that weighing them Monday and Thursday works, and I just use the most recent weight for the dose.
Good Day
Please i want you to revise the above weight ( 180+/-20 g) NOT kg ...
As you have a SD up to 20 g, so if the increase in BW is still within the 20 g, you don't have to change the dose if injected intraperiotneal or given by oral gavage. Taken into consideration that many drugs induce weight gain as an adverse effect. --> very important to be reported in the pre-clinical studies.
so you report it as one of your findings while you administer this dose throughout the duration of the experiment and observe the desired efficacy , if maintained or reduced while there is an increase in BW. Any change in dose will bias the results as you need to test the new dose in another group of rats weighing another BW.
So please refer to the following important and valuable chapter concerning dosing in rats by different routes:
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