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7 Types of Dissolution Apparatus

The 7 types of dissolution apparatus are officially recognized by the United States Pharmacopeia (USP <711> and <724>), and are widely used in pharmaceutical testing to evaluate drug release from various dosage forms. These standardized apparatuses simulate conditions for in vitro dissolution testing.

Here are the 7 types, including their common names, USP designations, typical uses, and key features:

1. Apparatus 1 – Basket Type (Basket Apparatus) A rotating basket (usually stainless steel mesh) holds the dosage form and rotates in the dissolution medium. Common uses: Capsules, floating tablets, and some extended-release formulations. Typical rotation speed: 50–100 rpm.
2. Apparatus 2 – Paddle Type (Paddle Apparatus) A paddle stirs the dissolution medium, with the dosage form placed at the bottom of the vessel (often with sinkers if needed). Common uses: Most widely used for immediate-release tablets, capsules, suspensions, and many solid oral dosage forms. Typical rotation speed: 50–75 rpm.
3. Apparatus 3 – Reciprocating Cylinder (Bio-Dis or Reciprocating Cylinder Apparatus) Dosage forms are placed in cylindrical tubes with mesh ends that reciprocate (move up and down) through the medium. Common uses: Extended-release (beads, pellets), modified-release products, and formulations requiring pH changes to mimic GI transit.
4. Apparatus 4 – Flow-Through Cell (Flow-Through Cell Apparatus) Medium flows continuously through a cell containing the dosage form (open system, often with fresh medium supply). Common uses: Poorly soluble drugs, extended-release formulations, powders, implants, and situations needing sink conditions or large volume simulation.
5. Apparatus 5 – Paddle Over Disk (Paddle Over Disc) A modification of the paddle method with the dosage form fixed on a disk at the bottom, and the paddle stirring above it. Common uses: Transdermal patches and topical systems.
6. Apparatus 6 – Rotating Cylinder (Cylinder Apparatus) The dosage form is wrapped around or attached to a rotating cylinder. Common uses: Transdermal patches and adhesive dosage forms.
7. Apparatus 7 – Reciprocating Holder (Reciprocating Disc or Reciprocating Holder) Dosage forms are held in various holders (disks, rods, springs, etc.) that reciprocate vertically in small-volume vessels. Common uses: Extended-release oral forms, stents, drug-eluting devices, contact lenses, and other novel or small-volume dosage forms (e.g., medical devices).

Apparatus 1 and 2 are by far the most common for routine quality control of oral solid dosage forms (tablets/capsules), while the others (3–7) are more specialized for modified-release, transdermal, poorly soluble, or non-oral products.

These are harmonized across major pharmacopeias (USP, Ph. Eur., JP) for the core types, though some regional variations exist in numbering or details.