Dissolution testing rotating basket method

Figure 12.2 The rotating basket and rotating paddle versions of the official method for dissolution testing of solid oral dosage forms, (a) The rotating basket - method 1, USP/NF. This method is official for USP/NF and BP. Current specifications describing geometry and positions for each compendium are shown, (b) The rotating paddle - method 2, USP/NF.

Dissolution testing of indapamide is accomplished using the rotating basket method (USP Method I) with 900 mL of simulated gastric fluid T.S. without enzymes heated to 37<>C as the dissolution medium and a basket rotation of 100 rpm. Samples are placed in the baskets and the baskets are then lowered into the dissolution medium with samples withdrawn at appropriate intervals. The samples are filtered through 0.45 pm Miilipore filters. The dissolution medium is assayed for indapamide against appropriate standards using an UV absorbance assay (23). 

As a general guideline in the choice of dissolution test apparatus, the simplest and most well-established method should be chosen, with respect to both in-house know-how and regulatory aspects. In most cases, this is the USP II paddle method or the USP I rotating basket method. However, if satisfactory performance cannot be obtained by these methods, others should be considered. Primarily, the USP III and USP IV methods, and non-compendial methods could also provide relevant advantages. 

Dissolution tests were performed with the rotation basket method, with 900 ml of 57 water at 50-100 rpm, according to USP XX and XXI. / /. he dissolved pharmacon content was measured spectrophotometrically /Spektromom 195 instrument/ and the CD content was measured in solution with concentrated sulphuric acid and anthrone at 625 nm /8/. 

Rotational Speed. The rotational speed of a basket or paddle is an important consideration in the development and validation of the dissolution test. A speed of 100 rpm is commonly used with the basket apparatus and a speed of 50 rpm is used with paddles. In method validation, one needs to ensure that slight variations in rotational speed will not affect the outcome of the dissolution test. The compendial limit for variations in rotational speed is 4%, but a wider variation (e.g., 10%) may be considered in testing the robustness of the method. 

USP Apparatus 1 (rotating basket) and 2 (paddle) are the first choices when developing a dissolution method for solid oral dosage forms. Even though the compendial equipment may not be suitable for all low-dose drug products, a brief discussion of these apparatuses is necessary in order to understand the basic operation of dissolution testing. 

The release tests were performed using the USP dissolution method (apparatus I) and utilized 1000 ml of pH 1.2 simulated gastric fluid (USP XXI) or pH 6.8 simulated intestinal fluid (USP XXI) without enzymes, equilibrated to 37°C and stirred with the basket rotating at 50 or 150 rev/ min. Drug concentrations were assayed by UV spectrophotometry at 255 nm. The experiments were continued until 100% dissolution was achieved. The release data were analysed to zero order, calculating the slope and intercept of the line. Each data point is the average of six individual determinations. In all cases the standard deviation was less than 9%. 

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