What is the best method of preparation for the next formula? Benzoyl Peroxide 5% erythromycin 3% Ethanol 94 ° 3% Propylene glycol 8.5 g Carbopolgel ad 50g

At least up to a certain concentration, there is between alcohol and carbomer no incompatibility. But there is an incompatibility between Carbopol and erythromycin (see table of incompatibilities in the booklet ' Galenic Formularium '. The composition, which you must make is Loco Benzamycin. But to avoid the incompatibility, which we notice when preparing Benzamycin, we do not dissolve the erythromycin in ethanol-propylene glycol. The preparation is therefore quite straightforward. We take into account an overdose because of the instability of the two products.

Preparation method

• Tarreer a mortar with a pestle.
• weigh the various components separately. Apply successively in the mortar 60 mg sodium lauryl sulfate, 4.40 g hydrated benzoyl peroxide to 75%, 0.42 carbomer 974p and 2.16 g erythromycin. Mix carefully after each addition. Add 6 g of propylene glycol and rub for several minutes in order to obtain a homogeneous clump of free paste. Dissolve 0.36 g trometamol in 10 ml freshly boiled and cooled purified water. Add this solution to the paste in the mortar and mix.
• successively add twice 10 ml freshly boiled and cooled purified water and mix carefully after each addition.
• fill up to a mass of 60 g with freshly boiled and cooled purified water; Keep in mind the tare mass; homogenize.
• Apply the gel twice through the ointment roller, reducing the free space between the rollers at the second treatment.
• homogenize again and pack 50g of the preparation into a tube.