Question
Posted on: March 6 2013Foaming in a trimethoprim suspension. Trimethoprim 1g glycerol 7g carbomer TMF 0.25% sorbitol 30ml after saccharinate Q.S. Banana Aroma Q.S.
When making this preparation, it does not allow foaming. It is not a flotation, but rather a thick soapy foam layer on the surface of the suspension. What could be the cause of this?
Answer
Foaming always indicates surface-active properties. This means a connection with a polar head and a lipophilic tail. Trimethoprim may react with saccharinate. Perhaps rather a complex than a salt. Because a salt seems chemically not kosher. And complexes of Saccharin are described in the literature. Of course, Carbomer will have an influence on the stability of the foam, due to increased viscosity.
In The new TMF, a trimethoprim suspension is also published, the composition of which differs slightly from the above formula. Carbomeer is replaced by 150mg xanthan gum; There is 100mg Polysorbate 80 added together with banana aroma and 50g aqua Conservans. There is no nasaccharinate in the composition but the volume is charged at 110g (= 100ml) with non-crystallizable sorbitol.
I have not heard of foaming with this formula. This composition contains a surfactant without discussion but I suspect that the viscosity of the TMF suspension is lower, so that less air is enclosed.