|
Easy Dose
Calculations
Many alpaca owners
are nervous when it comes to drug calculations.
This article will outline the common concepts
related to drug calculations and walk you through a few
exercises. By understanding these basic conversion factors and
formulas, you will be able to calculate drug doses for your
alpacas with confidence.
Let's Getting
Started
The
amount of active ingredient in a drug is commonly referred to
as its strength. For example,
an extra strength Tylenol capsule contains 500mg of
active ingredient. Therefor, 500mg is its
strength.
For
liquid drugs, both oral and injectable, concentration is an important factor in dosing.
Concentration refers to the amount of active drug
(strength) in a given volume of vehicle, usually a
liquid, but could be a paste, etc. For example, the
concentration of Panacur suspension is 100mg/ml. This
means that in every 1ml of liquid there is 100 mg of active
drug.
Concentration =
Strength / Volume
Concentration
= 100mg / 1ml
Another
factor that is often required when calculating doses is the
animal's weight. The weight
of the animal affects how the drug is absorbed, distributed
into the tissues and utilized by the animal's
body. Generally, the more the animal weighs, the
more drug is required for the desired effect.
It is important to use an accurate weight in your
calculations, otherwise, you may be giving too little or too
much medication (see article on
importance of weighing).
Recommended
Doses
Because weight is
such an important factor, most drug dosages you will see in
reference tables and prescribed by your vet will be written as
giving so much drug (strength) per pound (lb) or
kilogram (kg) of body weight. For example, you will see
the prescribed dose of Ivomec often expressed as 1 ml / 70
lbs. This simple means that a 70 lb alpaca needs 1ml
Ivomec. But what if your alpaca doesn't weigh 70
lbs.? This is where we need to use a simple formula to
determine the amount to give.
Suppose
your alpaca weighs 165 lbs. Here is the formula to
use:
weight
of alpaca x prescribed
dose = amount
to give
|
165
lbs.
x |
1ml |
=
|
165
lbs.
ml |
= 2.4
ml
|
|
70
lbs.
|
70
lbs. |
(Remember
when multiplying fractions you multiply the numerator (top
number)
and divide by then denominator. The same units above and below the line cancel
out)
Because
the Metric system of measurement is commonly used in the
sciences, often you may come across dose recommendations that
are based on kilograms (kg) not pounds (lbs.). You could set your
scale to weigh in kilograms so you don't have to convert units
of measure, but most of us are more familiar with pounds. So, we need to convert
the weight of our alpaca to kilograms and then use the formula
above.
For
example, you are told to dose your alpaca at 1ml / 32 Kg. Your alpaca still
weighs 165 lbs.
Here is the conversion formula:
|
Weight
in Kg
= |
Weight in
lbs. |
|
2.2 |
|
or |
|
|
75 kg = < /FONT >
|
165
lbs. |
|
2.2 |
Now
that we know our alpaca weighs 75kg, plug the numbers into the
same formula we used above:
weight
of alpaca x
prescribed
dose =
amount
to give
|
75
Kg
x |
1ml |
=
|
75
Kg
ml |
= 2.3
ml
|
|
32
Kg
|
32
Kg |
The
above formulas work well when you are instructed to give a
certain volume (ml) of medication based on weight of
your alpaca. But
suppose your vet already knows the weight of your alpaca and
she tells you to give so many milligrams (mg) of a liquid
medication. In
this case, you need to use a slightly different
formula.
For
example, you are told to give your cria 150mg of SMZ
orally. You look
on the bottle and see the drug concentration listed as 200
mg/5ml. Remember
that:
Concentration
= Strength / Volume
So,
200mg =
the strength and 5ml = the volume. With that in mind,
here is the formula:
|
prescribed
dose
strength |
x
volume = |
= amount
to give |
|
|
or |
|
|
|
|
150
mg
200
mg |
x
5 ml = |
750
mg ml
200
mg |
= 3.8
ml |
|
|
|
| |
Remember:
Before doing the calculation, convert units of measurement to
one system.
Common
Conversions:
1
Liter = 1000 ml
1 ml
= 1cc
1 Gram = 1000 mg
1 kg = 2.2 pounds
Well, that's all there is to it. By mastering
this simple equation, you'll be able to calculate the dose
that will help get your alpaca back to a state of health!
|
