The drug concentration to be given to the rat is 400mg/kg. If I prepare the 8% stock drug solution, 4gm of the extract is dissolved in 50ml of the solvent. Theoretically, if I take 1 ml from the prepared stock drug solution, it should possess 80mg of the drug. For instance, I assume that if I want to administer 160mg of the drug to a rat, I have to take 2 ml of stock drug solution. It is obvious that 2ml of stock drug solution consists of 160mg of the drug, only when the drug has 100% solubility in a solvent (homogeneous solution). How can I confirm the solubility of the given drug in a given solvent? Is there any protocol?
Dear Shanmuganathan,
Because the drug used is the extract. You've to do the quantitative analysis to know exact amount of active substance that dissolved. If you only investigate that there is no precipitate, it can't confirm the 100% solubility of active substance in extract.
Moreover, in stock solution preparation, you'd dissolve 4 g of extract in 3/4 (or 2/3) of solvent before adjust to the final volume of 50 mL.
Regard,
Ekapol
Oral administration dosage is not calculated based on the per cent solubility of crude drug. If the quantity to be given is 160mg/rat (I assume that you have calculated assuming that the body weight of a rat is 250g), then check whether that 160g is soluble in 1 ml of vehicle. It not increase the volume to 2 ml. You may not be able to increase the volume to more than 2.5 ml max, since more than that is not recommended to be given in a rat as single dose. If not soluble, use any other suitable non toxic, non irritant and non reacting solvents.
If it has to be given to multiple number of animals (say 6 animals) then add up the requirement of each animal, add up the solvent and then calculate the volume to be given to each animal, to meet the dose.
The equilibrium solubility of your drug must be determined by the following protocol:
1-Add excess amount of drug to distilled water or your solvent but in the case of biological, it will be distilled water where it is left to be stirred (magnetic stirrer) or continously shaked (rotary shaker) for 48 or 72 hours at 37 degree celsius (temperature of body) until equlibration. If, completely dissolved during this period, add another excess amount of your drug again.
2-Filter this suspension through sample filter or Whatmann filter paper then discard the first 2 or 3 mls to minimize analysis fault due to adsorption of drug.
3-Take cetain volume of your filterate, then analyze it directly or after diluting (depending on the linearity of your validated analytical method.
4-Calculate the amount of drug dissolved per mls of your solvent to know drug solubility.
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