Calculating Doses of Medicines

28.10 Calculating Doses of Medicines The dose of a medicine refers to how much, how often, and how many days a medicine is given. Use the following steps to calculate the amount of medicine to give.

Step 1 Determine the body weight of the animal. See Pages 36-41.

Step 2 Find out the dose of the medicine. If the dose is given in mg/kg (milligrams per kilogram), use step 3. If the dose is given in ml/kg, then skip to step 4.

Step 3 Calculate the weight of medicine needed for that dose.

Dose (mg/kg) X weight (kg) = total number of mg of medicine needed for that dose.

73 For example: if the dose is 20 mg/kg, and the goat weighs 20 kg, then:

20 mg/kg X 20 kg = 400 mg of medicine needed for that dose.

This means that a 20kg goat needs 400 mg of medicine.

If the medicine is in powder (solid) form, your calculation is finished. Simply give the 400 mg of medicine (usually mixed in the feed or water) to the goat at the specified frequency and number of doses.

If the medicine is in liquid form, an additional calculation is necessary to know the volume of medicine to give. For this additional calculation, you will need to know the strength of the medicine.

Calculate the volume needed using the following information:

- weight (mg) of medicine needed and - strength of the medicine. This is always listed on the bottle of medicine and is usually listed in mg/ml. To include the strength as a factor in the formula, simply invert the fraction. For example, if the bottle of oxytetracycline has a strength of 100 mg/ml, invert it to 1 ml/100 mg when calculating the volume needed below.

Volume needed in ml = (Total number of mgs needed) X (strength in ml/mg)

74 For example: the 20kg goat in the previous example needed 400 mg of medicine. If the strength of our liquid medicine is 100 mg/ml, the volume of medicine needed is:

400 mg X 1ml/100 mg = 4 ml of medicine needed Therefore, give the goat 4ml or 4cc of medicine.

Step 4 If the dose is given as ml/kg, all you need is the weight of the animal to calculate the volume of medicine needed with the following formula:

Dose (ml/kg) X weight (kg) = ml medicine required 75 For example, if the dose is 2 ml/kg and the a pig weighs 30 kg, then:

2ml/kg X 30kg = 60ml or 60cc of medicine needed Simply give the pig 60cc of the medicine.

Note: If it is an injection, it should be divided up and given in at least three different sites on the pig. Don’t give more than 20 cc of medicine in any injection site.