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Determination of dissolution profiles of solid dosage form

Objectives:

1. To determine the dissolution profile for Paracetamol tablets.

2. To determine the dissolution profile for Tetracycline HCl capsules.

3. To practice literature search (In-lab assignment).

Introduction:

Dissolution is the transfer of molecules or ions from a solid state into solution. The

dissolution of a solid in a liquid may be regarded as being composed of two consecutive

stages. First an interfacial reaction that results in the liberation of solute molecules from a

solid phase (release) into the boundary layer which becomes saturated (Cs). After this, the

solute molecules must migrate through the boundary layers surrounding the crystal to the bulk

of solution, at which time its concentration will be C. This step involves the transport of these

molecules away from solid-liquid interface into the bulk of the liquid phase under the

influence of diffusion. An equation known as the Noyes-Whitney equation was developed to

define the dissolution from a single spherical particle. dm/dt = D A (CS-C)/h, where dm/dt is

the rate of mass transfer of solute molecules or ions through static diffusion layer dm/dt, A is

the area available for molecular or ionic migration, CSC is the concentration difference

across the diffusion layer, h is the thickness of diffusion layer, D isthediffusion coefficient

in cm2/s. If the volume of the dissolution medium is so large that C is not allowed to exceed

10% of the value of Cs, dissolution is said to occur under sink condition, in vivo (drug is

absorbed from its solution in the GIT at faster rate than it dissolves from a soliddosage form.),so equation will be reduced to dm/dt= DACS/h. Dissolution test is done for each dosage form,

in accordance with certain requirements stated in each monograph for a tablet or capsule. The

type of dissolution apparatus, there is two types, apparatus I, (rotating basket), where a solid

dosage form is placed inside a stainless steel wire basket, which is rotated at a fixed speed

while immersed in the dissolution medium, which is contained in a wide- mouthed cylindrical

vessel. Apparatus II (paddle), where the dosage form is allowed to sink to the bottom of the

dissolution vessel, and agitated using rotating paddle.

General Procedure:

Place the stated volume of the dissolution medium in the vessel of the apparatus specified in

the individual monograph, place solid dosage form, and immediately operate the apparatus at

a rate specified in the individual monograph. Within the time interval specified, withdraw a

specimen from zone midway between the surface of the dissolution medium and the top of the

rotating basket or blade, replace the aliquots withdrawn for analysis with equal volumes of

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fresh dissolution medium at 37C0or, where it can be shown that replacement of the medium is

not necessary, correct for the volume change in calculation.

Experimental:

1-Dissolution test of acetaminophen tablet:

The test is applied on Paracetamol 500 mg tablet.

1- Place 900 ml pH 5.8 phosphate buffer in the vessel of apparatus II, at temperature of370C.

2- Place one tablet in the vessel, and operate the rotation of paddle at 50 rpm.

3- Each 5 min, withdraw 10 ml specimen for 30 min, from zone midway between the surface

of dissolution medium and the top pf the rotating paddle.

4- Filter, make the proper dilution if needed, then measure the absorbance at 243 nm.

5- Calculate the total amount of Paracetamol in each specimen using the calibration

equation, Absorbance =61.36 conc (mg/ml). 0.016

6- Plot the amount of paracetamol released vs time

2- Dissolution test of Tetracycline HCl 250mg capsule.

1- Place 900 ml of 0.1 N HCL in the vessel of apparatus II, at temperature of 370C.

2-Place one capsule in vessel, and operate the rotation of paddle at 75 rpm.

3-Every 10 min, withdraw 10 ml specimen for 60 min, from zone midway between the

surface of dissolution medium and the top pf the rotating paddle.

4-Filter, make the proper dilution if needed, then measure the absorbance at 353 nm.

5-Calculate the total amount of tetracycline HCL in each specimen, taking 310 as the value of

absorbance of standard solution (1%, 1cm) at 353 nm.6- Plot the amount Tetracycline released vs time

Practical:

1. Carry out the assigned dissolution experiment within your group.

2. Make appropriate calculations and plot the amount released vs. time for both products.

3. In-lab assignment (literature search).