BRIEFING THE FORMULATION OF CONTROLLED RELEASE DOSAGE FORMS

CONTROLLED RELEASE DOSAGE FORMS –

Controlled release dosage forms are the pharmaceutical dosage forms which release the drug slowly into the systemic circulation and thereby it prolong the pharmacological activity of the drug.

The advantages of Controlled release dosage forms over the conventional dosage forms –

1)    To reduce the frequency of dosing

2)    To increase the patient compliance

When we will go for designing a Controlled release dosage is –

1)    When the drug is having very short biological half – life

2)    When the drug is stable in both the acidic and basic pH in the GIT

3)    When the drug is absorbed into the systemic circulation throughout the GIT

Materials used for formulating a Controlled release dosage forms –

1)    Controlled release polymers (both Hydrophilic and Hydrophobic polymers) as matrix systems

2)    Converting the drug molecules into low water soluble salts (for example - conversion of water soluble salts likes hydrochlorides and sulfates into low water soluble salts like stearates)

3)    Osmotic pump systems and many more

Formulation development of a Controlled release dosage form using Controlled release polymers (both Hydrophilic and Hydrophobic) as matrix systems –

Let us take an example and explore the way to formulate

Matrix is a non - retardant material which prevents the release of drug from the system. Let us take Propranolol Hydrochloride as a drug molecule and HPMC (K100 M), (K50 M) and Ethyl Cellulose as matrix formers

Propranolol Hydrochloride is highly soluble and highly permeable drug which comes under BCS – I Classification. It is absorbed into the systemic circulation throughout the GIT. It is having short biological half – life of about 3.5 hours and requires more than 3 doses per day in some patients.

HPMC (K100 M) and HPMC (K50 M) are Hydrophilic bio - polymers whose viscosity is 10,00,000 Cps and 50,000 Cps respectively. We are taking the polymers of this high viscosity in order to control the release if we take the HPMC with lower viscosity grade it will not control the release due to its low viscosity and low gelling nature. Whenever the gelling nature is low the polymer get eroded soon and the drug is released rapidly into the systemic circulation.

Ethyl Cellulose is a Hydrophobic polymer and it is porus and it is generally mixed with Hydrophilic polymers to retard the release from the matrix of Hydrophilic polymers

Take Microcrystalline cellulose as diluents (Avicel pH 102)

Take Magnesium stearate as Lubricant.

Develop several formulations varying the ratio of drug : polymer and the overall weight is adjusted using diluent.

Perform stability studies keeping the powder mixture of different formulations in vials and stored at 30 ± 2⁰ C and 75 ± 5 % RH for 60 days and performed FTIR analysis on those samples for evaluating the drug – excipient compatability.

Perform Pre – compression studies like Bulk density, Tap density, Hausner’s ratio and Carr’s Index and found that the powder mixture of different formulations and found that the powder is having very poor flow properties.

Hence there is no chance for Direct compression method.

We can’t go for wet granulation method using purified water as granulating agent because these Hydrophilic polymers will absorb water and swell. Hence, we can’t go for wet granulation method using purified water.

Next alternate is to go for wet granulation method using any organic solvent like Isopropyl Alcohol as granulating agent.

Pass all the ingredients through sieve number 20 separately. Take these ingredients according to their ratio’s in different formulations in a mortar and pestle and mixed thoroughly. While mixing added Isopropyl Alcohol slowly until granulation consistency is achieved. The obtained blend is passed through sieve number 12 and dried them in a hot air oven.

Later the dried granules are passed through sieve number 16.

If the obtained granules are big in size and if we punch the tablets the tablets may break as laminates. If the obtained granules are small in size and if we punch the tablets the tablets will have high hardness.

Hence, we needed granules with average size and some small granules to fill the gaps between the compressed material during punching.

The tablets are obtained with required hardness and some of them are charged for stability studies and dissolution is performed on some tablets. The tablets shows extending the release for 24 hours.

If the tablets don’t shows extending the release upto 24 hours then use Ethyl cellulose in different ratios in the formulation and try to prolong the release.

There is no marketed controlled release formulation for this Propranolol Hydrochloride hence we cannot able to caliculate f2 value.