Posted: 1/18/2014

Dosage calculation

Pneu-Dart does not condone nor promote the extra-label use of veterinary pharmaceuticals unless on order and under supervision of a licensed veterinarian.

The pharmaceutical industry in this country has not been very responsive to the needs for safe, effective, and less costly drugs for animal restraint or immobilization. Some progress has been made over the past twenty years, but there is still a long way to go before the ideal immobilization drug may become available. In the meantime, the worker should become adept in using the products currently in the market.

The responsibility for the correct use and storage of the drugs rests entirely with the user. This includes the worker, the veterinarian responsible for obtaining and dispensing the drug, and, finally, the agency. The manufacturer of these drugs will not be liable or assume any responsibility for the use, misuse or possible abuse of their products.

Dosage calculation

In order to correctly calculate the drug dosage required to immobilize a particular animal, the worker must know three factors.

  1. Estimated weight of the animal. If the weight of the animal is estimated in pounds (lbs), it should be converted to kilograms (kg), as dosages are expressed in mg/kg (milligram of drug per kilogram of body weight) required to produce immobilization. One pound equals .454kg, and the conversion is made by multiplying the estimated pounds by .454. Thus a 100lb animal weighs 45.4kg. Since 1lb is almost equal to 1/2kg, a simpler conversion can be made by dividing the estimated weight in pounds by 2. By this method the 100lb animal weighs 50kg. Because of the difficulty in accurately estimating the weight of an animal and the safety margin of the CNS drugs, this simpler conversion is acceptable for fieldwork.
  2. The dosage recommended for the species. This is the dosage recommended to produce immobilization in a particular species. Dosage recommendations may be provided by a veterinarian, by the drug package insert, or by consulting dosage tables in reference literature. The suggested dosage tables are given in mg/kg (milligram of drug per kilogram of body weight).
  3. Concentration of the drug used. The concentration (solution strength) of the drug is listed on the label of the vial, on the package, and in the package insert. It is given as mg/ml (milligram of drug per milliliter of liquid volume). To minimize the drug volume, and consequent size of the RDD, the highest available concentration of a given drug should be used.

For all practical purposes, 1ml (milliliter) is equal to 1cc (cubic centimeter) of liquid volume. On the basis of these three factors, the drug dosage is calculated as follows:

Animal weight (kg) x dosage (mg/kg) / concentration of drug (mg/ml) = drug volume in ml or cc.

The manner in which a drug may effect an animal and the level of immobilization produced are subject to a number of factors. In addition to the animal’s weight, its age, sex, physical condition, and mental state at the time of injection, individual animals will have varying degrees of sensitivity to the drug. This can produce different and unexpected results from one individual to another, even within the same species. Excitable animals will usually require a higher dosage than animals which are calm. Also females may require a higher dosage than males to produce a satisfactory level of immobilization.