Question
Posted on: March 6 2013Discoloration of a mouth rinse agent with tetracycline.
The solution (mouthwash) prepared according to the following formulation discolours after a few days from light to dark brown despite the doctor's recommended Brown bottle. Can this discoloration be avoided?
R/tetracyclineHCl 4 G
nystatin 300,000 E
tragacanth 1.5 g
sodium cyclamate 1 g
water 40 g
Glycerin 5 ml
vanillin syrup to 100 ml
Answer
This composition corresponds to the tetracycline suspension from the NF VI after omitting the nystatin. However, the doctor has omitted an important excipients, the disodium hydrogen phosphate. It should be added so that the dissolved tetracycline precipitates in the form of a yellow precipitate and becomes much more stable. The amount of disodium hydrogen phosphate 12 aq. (3 g per 100 ml syrup) must be correct so that the pH set corresponds to the minimum solubility of tetracycline in water.