Different types of dissolution test apparatus are used for dissolution testing according to USP, BP, and IP.
The dissolution test apparatus is a device used to determine the active pharmaceutical ingredient (API) in pharmaceuticals such as tablets, caplets, or capsules for the preparation of any drug according to USP, BP, and IP specifications. It calculates adequate bioavailability and gives the necessary information in the development of solid dosage forms.
The dissolution testing is used as an official test by pharmacopoeias for the evaluation of the drug release of Capsule and tablet, etc. Dissolution testing is an important analytical procedure usually checked for the quality control, stability, and evaluation of the batch-to-batch consistency of the product.
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Before a drug can start acting pharmacologically on the patient in form of solid dosage forms such as tablets or capsules, it should be first dissolved in the stomach before being absorbed into the bloodstream. This apparent first step could prove challenging for drug development. The dissolution test apparatus is therefore essential to give significant information on the in-vitro release of drugs to anticipate their behavior in-vivo.
The oral solid dosage form is still the most frequent method/route of drug administration, the rate at which the drug is released into the body after the dissolution of the dosage form has been swallowed is an important feature of drug development.
Types of dissolution test apparatus as per USP:
- Rotating basket type apparatus-Apparatus I
- Paddle type apparatus-Apparatus II
- Reciprocating cylinder type apparatus-Apparatus III
- Flow-through cell type apparatus- Apparatus IV
- Paddle over disk type apparatus- Apparatus V
- Cylinder type apparatus- Apparatus VI
- Reciprocating disk type apparatus- Apparatus VII
Types of dissolution test apparatus as per IP:
- Paddle type apparatus- Apparatus I
- Basket type apparatus- Apparatus II
Types of dissolution test apparatus as per BP:
- Basket Type apparatus- Apparatus I
- Paddle Type apparatus- Apparatus II
- Flow-through cell type apparatus- Apparatus III
Overview on types of dissolution test apparatus:
There are seven USP- types of dissolution apparatus such as rotating basket type, paddles type, reciprocating cylinders, flow cell type, paddle over the disc, cylinder type, and reciprocating disk type apparatus. These are used in the pharmaceutical industry, research laboratories to provide important in-vitro drug release information for both quality control purposes.
Rotating basket (USP Apparatus 1):
It is commonly referred to as a rotating basket since it smoothly rotates and its speed complies with USP recommendations. It consists of a cylindrical basket (capacity of up to 1000 ml) which is held by a motor shaft (made of stainless steel), and the shape is semi-hemispherical at the bottom. The sample is placed in the basket, which rotates up to 100 rpm in a circular flask filled with dissolution medium. The entire flask is immersed in a constant bath temperature at 37°C. The apparatus-1 is generally preferred for capsules, suppositories, and for dosage forms that float or disintegrate slowly (delayed-release).
Paddle type (USP Apparatus 2):
Paddle type is the most widely used dissolution apparatus. It consists of specially coated paddles which reduces the disturbance due to stirring. The paddle vertically comes in contact with the bottom of the shaft and is connected to a motor that rotates at a set speed. The sample (tablet/caplet/capsule) is placed in a dissolving flask with a circular bottom to reduce the turbulence of the dissolution medium. Its operating motor speed is usually at 40 and the operating temperature is 37oC.
Reciprocating cylinder (USP Apparatus 3):
This apparatus is based on the disintegration tester and more suitable for extended-release, chewable tablets. It consists of a set of cylindrical, flat-bottomed glass outer vessels, and a set of glass reciprocating inner cylinders. Fittings and screens are made of stainless steel and other suitable materials that fit the tops and bottoms of the reciprocating cylinders.
Flow-through cell (USP Apparatus 4):
The flow-through method allows the system to be set into two types as an open system and a closed system. It consists of a reservoir for the dissolution medium and a pump that pumps the medium through the test sample-holding cell. The medium is maintained at operating temperature 37°C with flow rates ranging from 4 to 16 ml/min and up to the six samples can evaluate. The flow through the cell apparatus is used to evaluate modified-release dosage or is typically employed for low-dose medication.
Paddle over the disk (USP Apparatus 5):
It consists of a shaft and a disc assembly that can hold the sample so that the surface can be leveled with a paddle. It is most commonly used for transdermal delivery systems that are attached to a stainless steel disc, which is then placed directly on the bottom of the vessel, under the paddle.
Rotating cylinder (USP Apparatus 6):
The cylinder type apparatus is used for testing transdermal patches. It consists of a stainless steel cylinder which is used to hold the sample. Generally that sample is mounted on to cuprophan. The sample is placed inside the cylinder and will be extracted from the outside into a water bath.
Reciprocating disk (USP Apparatus 7):
The reciprocating disc equipment is suitable for small dosages and is ideal for controlled release formulations, and dosage forms that requiring a change of media. It consists of a motor and drives assembly that turns the system vertically and also consists of a volumetrically calibrated solution. A flat-bottomed cylinder-shaped vessel with a volume capacity of up to 200 ml is used in this apparatus.
Commonly asked questions on dissolution are as follows.
What is the principle of dissolution?
The significant operating principle of the paddle/basket dissolution apparatus is to offer a specific and controlled rotates and mixing mechanism at 37°C.
Which is the most widely used dissolution apparatus?
Paddle type (USP Apparatus 2) is the most commonly used apparatus for dissolution testing since it can be used for a wide range of dosage forms.
Which tablet is used in the calibration of dissolution?
The dissolution test is calibrated with Prednisone and Salicylic Acid Tablets USP, prednisone specifically for the disintegrating type, while salicylic acid is specifically for the disintegrating type.
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