A cream based on betamethasone dipropionate breaks down.

A few remarks can be formulated regarding this composition. As a starting point of the discussion, reference can be made to analogue compositions in the TMF. These contain neither Tween nor salicylic acid. PEG derivatives like here Tween and also cetomacrogol are incompatible with molecules, which are carriers of a phenol function such as salicylic acid. A larger amount of salicylic acid will be in this cream base in solution compared to the solubility in pure water. After all, the salicylic acid will react with the buffer, present in the cream, with formation of salicylate and altering the pH of the cream. The presence of Tween 80 also gives rise to the solution of salicylic acid. Both: Salicylic acid and salicylate, can thus react with the emulsifier of the cream especially Cetomacrogol. And I think this is the basis of the gradual breaking of the cream. Maybe the current high temperatures are also there for something? But equally important is the pH change that occurs due to the neutralization of the buffer by the acid salicylic acid. The Cetomacrogol cream was buffered to increase the stability of the corticosteroid esters! A check of a series of pharmaceutical creams, which contain Cortico's, teaches me that they contain a buffer but not salicylic acid! This is true with my prior comment. Why an analogue cream based on Clobetasol propionate, but prepared without using a trituration, does not break I can not explain.

Conclusions

1. It is recommended not to add salicylic acid and to use the validated compounds as mentioned in the TMF without salicylic acid and without a Tween 80;
2. to work with secundum Artem and to ensure a good homogeneity of the drug, a trituration should be used for both creams. The preparation of a 10% trituration lies within the possibilities of the Officina-pharmacist. The procedure of the TMF can be followed;
3. If you want to continue with the preparation according to the specified formula, the pH of the cream should be checked and it should be set to pH = 4.5 to 5 In addition to hydrolysis, a rapid isomerisation of Betamethasone Dipropionate at a loss of 85% of efficacy within five days;
4. Perhaps it also pays to find out whether the use of triturations based on lactose monohydrate brings a solution?

Preparation of a trituration 10% according to TMF

composition

R/corticosteroid 1.00 g Lactose monohydrate or mannitol Q.S. ad 10.0 g

PREPARATION MODE

• Tarreer a mortar with pestle, both with smooth surface.
• weigh the active ingredient separately.
• rub in this mortar about 1g lactose monohydrate or mannitol finely.
• Add 1.00 g corticosteroid and rub this carefully with the contents of the mortar.
• then add, in small quantities, the remainder of the lactose monohydrate or mannitol and fill up to 10.0 g; Keep in mind the tare.
• Homogenize after each addition.
• pack the trituration into an airtight sealed receptacle.