Dissolution apparatus Reciprocating cylinder

Rohrs BR. Calibration of the USP 3 [reciprocating cylinder] dissolution apparatus. Dissolution Technol 1997 4(2) 11—18. 

Various dissolution test systems have been developed and several of them now enjoy compendial status in pharmacopeias, for example the reciprocating cylinder (United States Pharmacopeia Apparatus 3), the flow-through apparatus [European Pharmacopoeia (Pharm. Eur.) 2.9.3], or the apparatus for transdermal delivery systems, such as the paddle over disc. Hydrodynamic properties of these and other apparatus have been described only sparingly. The paucity of quantitative data related to hydrodynamics of pharmacopeial dissolution testers is lamentable, since well-controllable hydrodynamics are essential to both biopharmaceutical simulations and quality control. Here, we focus the discussion on the paddle and the basket apparatus, since these are the most important and widely used for oral solid dosage forms. A brief treatise on the hydrodynamics of the flow-through apparatus completes this section. 

USP Dissolution Apparatus 1 (basket) and 2 (paddle) are commonly used for immediate-release formulations. USP Apparatus 3 (reciprocating cylinders) is the system of choice for testing extended-release products or a dosage form that requires release profiling at multiple pH levels and time points. Low-dose products may require the use of flow-through analysis or other low-volume test techniques (noncompendial 100- or 200-mL dissolution vessels). Once the apparatus is selected and has been shown to be suitable during method development, no further evaluation of another apparatus is required during validation. 

When using USP 23 Apparatus 3 (reciprocating cylinder), USP 23 Apparatus 4 (flow- through cell), or USP 23 Apparatus 7 (reciprocating disk) the above dissolution testing conditions should be modified accordingly. 

The preferred dissolution apparatus is 1 ISP apparatus 1 (basket) or 11 (paddle), used at compendially recognized rotation speeds (e.g., 100 rpm for the basket and 50-75 rpm for the paddle). In other cases, the dissolution properties of some ER formulations may be detennined with USP apparatus 111 (reciprocating cylinder) or IV (flow through cell). 

Numerous dissolution methods (not limited to those officially prescribed) must be available to ensure proper discrimination as well as the use of various media. The preferred dissolution apparatus is USP I (basket), II (paddle), or IV (flow through cell). USP apparatus III (reciprocating cylinder) could be considered in some cases. An aqueous medium, either water or a buffered solution preferably not exceeding pH 6.8 (or 7.2), is recommended, other pH must be justified. For poorly soluble drugs, the addition of a surfactant may be necessary. 

Fig. 6 Schematic of a USP 3 dissolution-testing apparatus, also referred to as reciprocating cylinder apparatus.

Wong D, Larrabee S, Clifford K, et al. USP Dissolution Apparatus n (reciprocating cylinder) for screening of guar based colonic delivery formulations. / Control Release 1997 47 173-179. 

The apparatus consists of a set of transparent cylinders, capped at each end with a screen, in which the dosage form is enclosed. The cylinders are gently moved up and down (the dip rate) in dissolution medium contained in glass tubes held in a water bath. The medium enters the cylinders allowing dissolution to occur. At the specified times the reciprocating cylinders are raised and a portion of the solution is removed for analysis. 

The USP also lists three other dissolution apparatus for transdermal delivery systems, apparatus 5 (paddle over disk), apparatus 6 (cylinder), and apparatus 7 (reciprocating holder). 

Reference tablets of known dissolution rate are available from the USP to determine apparatus suitability. Prednisone tablets (disintegrating) and salicylic acid tablets (nondisintegrating) may be used to check the calibration of the basket, paddle, and flow-through apparatuses. Chlorpheniramine extended-release tablets and theophylline extended-release beads have recently become available for checking the calibration of the reciprocating cylinder apparatus. 

For the dissolution testing of an amorphous dmg product, any of the test apparatus typically used for testing of solid oral dosage forms may be selected based on its demonstrated capability to provide meaningful drug-release data and to discriminate for critical factors. Typically, the basket and paddle apparatus are the most commonly used. However, the reciprocating cylinder apparatus and the fiow-through apparatus also may be used. 

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