Trituration Method
A trituration is a dilution of a potent drug powder with an inert diluent powder,
usually lactose, in a definite proportion by weight. We can then remove
a weighable portion (aliquot) of the mixture containing the desired quantity
of substance to maintain an acceptable range of accuracy.
Using ratio and proportion, we can determine the weight of drug and lactose
required to make the trituration as well as the weight of the aliquot to
be used to fill the prescription.
Keep in mind that any substance that must be weighed on the balance drug
(A), lactose (B-A), and aliquot (D) must be at least 120 mg.
Lactose is the most commonly used diluent in solid dosage form pharmaceuticals such
as powders, tablets and capsules. Some of the reasons included its extremely
low incidence of side effects, ready availability, and low cost.
Example: Make 10 capsules, each containing 0.6 mg Atropine Sulfate and
each weighing a total of 200 mg.
Make Trituration
1. Total weight atropine sulfate required (this is C in the proportion)
2. Select some multiple of 6 mg that can be weighed with the desired degree
of accuracy. (this is A in the proportion) (e.g. select multiple= 20)
3. Select the size of the aliquot portion to be taken to contain the 6
mg of drug. (this is D in the proportion)
4. Since we now have A, C, and D in our formula, we can solve for B(trituration
weight).
[Note: this should be the multiple (20) x the weight of the aliquot
(120 mg)]
5. Determine the weight of diluent (lactose) required to prepare the trituration
by subtracting the weight of atropine sulfate from the trituration weight.
6. Fill Rx:
Determine the weight of lactose which must be added to the aliquot portion of
trituration to complete the prescription, so that each capsule weighs 200
mg.
After the necessary calculations are completed, the trituration is prepared
using the following steps:
- weigh a suitable amount of drug (at least 120 mg), and reduce it to a
fine powder in a mortar (i.e., triturate it);
- weigh a suitable amount of diluent;
- mix the drug and diluent by geometric dilution and;
- weigh an aliquot of the trituration containing the desired weight of
drug.
View a video demonstration on geometric dilution
Hence the compounding procedure for this product is as follows:
