Capsule fill weight is determined applying following formula

Capsule fill weight is determined applying following formula:

Capsule fill weight = Tapped bulk density of substance x capsule volume

Example

A formulation has a theoretical fill weight of 325 mg and tapped bulk density of the substance is 0. 75 g/ml while bulk density of inert substance is 0.80 g/ml.

Given

1. Weight of substance in each capsule = 325.0 mg

2. Bulk density of substance = 0.75 g/ml

3. Bulk density of inert substance = 0.80 g/ml

Volume of size ‘ 1’ capsule = 0.48 ml (from Table.)

Volume occupied by drug = 0.43 ml (by calculation)

Volume unoccupied = 0.48 – 0.43 = 0.05 ml

Weight of diluent or inert substances = volume x bulk density

= 0.05 x 0.80 = 0.040 g = 40.0 mg

Send ten capsules of the given materials (Always weigh substance for one extra capsule as material is lost during powdering, mixing, and handling of the substance)

Weight for 11 capsule of substance = 325 x 11 = 3.575 g

Weight of diluent or inert substance = 40 x 11 = 0.440 g

Total weight of filling substance in the hard empty shell = 4.015 g

Example

Fill the substance containing drug in each capsule, of size ‘1’ capsule 280 mg of bulk density 0.70 g/ml. Determine how much amount of inert substance is required to fill 10 capsules while bulk density of inert substance is 0.85.

Example

Which number of capsule is to be used for 375 mg material having bulk density 0.75 g/ml. Bulk density of inert substance is 0.68. Calculate the total g/ml required for 10 capsules.

Given

Weight of substance in each capsule = 375.0 mg

Bulk density of substance = 0.75 g/ml

Bulk density of inert substance = 0.68 g/ml

For filling this volume of substance ‘ 1’ number capsule is most appropriate because

Volume of size ‘1’ capsule = 0.48 ml (from Table 9.1.)

Volume occupied by drug = 0.466 ml (by calculation)

Volume unoccupied = 0.48 – 0.466 = 0.014 ml

Weight of diluent or inert substances = volume x bulk density

= 0.68 = 0.040 g = 0.00952 g = 9.52 mg

Send ten capsules of the given materials

Weight for 11 capsule of substance = 375 x 11 = 4.125 g

Weight of diluent or inert substance = 9.52 x 11 = 0.105 g

Total weight of filling substance in the hard empty shell = 4.230 g