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D. FERREIRA Y COLS. ANAL. REAL ACAD. NAL. FARM

Preparation of naproxen microcapsules

After preliminary studies, the following optimal experimental
conditions were chosen for the preparation of naproxen microcapsules on
a dissolution apparatus (paddle method). Liquid paraffin (300 ml) was
placed on a vessel at 37ºC. A solution containing 0.75 g of naproxen, 2.5
g of polymer or mixtures of polymers, 0.0625 g of Cutina and 0.125 g of
magnesium stearate in 60 ml of acetone was added to paraffin through a
separating funnel. The mixture was stirred at 200 rpm. The resulting
emulsion was agitated at 37ºC for 4 h and during this time acetone was
evaporated. The resultant microcapsules were isolated by filtration,
washed with cyclohexan and dried at room temperature for 12 h.

The empty microcapsules were prepared using identical experi-
mental conditions but in the absence of naproxen.

The prepared formulations are shown in Table 1.

Table 1. Naproxen microcapsules formulations prepared by the solvent evaporation
process.

Formulations

Components A B C D E F G H

Naproxen 0.750 0.750 0.750 0.750 0.750 0.750 0.750 0.750

Eudragit RS PM 2.500 1.875 1.250 0.625 - - - -

Eudragit RL PO - 0.625 1.250 1.875 2.500 2.500 2.500 2.500

Cutina (0.0625 - - - - - HR KD 16 MD
g)

Magnesium 0.125 0.125 0.125 0.125 0.125 0.125 0.125 0.125
Stearate

Naproxen content
Naproxen microcapsules were weighed, dissolved in chloroform
and filtered. Naproxen was assayed by UV analysis using a calibration
curve at 331 nm.

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