Q. Would you be able to help us with providing a stable formulation of phenol 7.5% injectable solution for intrathecal instillation? We have a pain specialist who would like to use this for nerve blockade.
A. Phenol USP, or carbolic acid, (mw 94.11; d 1.071) occurs as colorless or faintly pink or yellow deliquescent crystals or more commonly as crystalline masses (fused crystals) because of its deliquescent nature. Fused crystals must be melted (preferably in a fume hood) to weigh the required quantities for compounding. Phenol USP is soluble in water, and miscible with ethanol, ether, and glycerin. It congeals at 41°C and melts at 43°C. It is incompatible with alkaline salts and nonionic surfactants. Precautions should be taken when handling phenol USP because it is corrosive and can cause toxic symptoms when absorbed through the skin or when the vapor is inhaled.
Phenol 7% in water was injected to block pain of trigeminal neuralgia. Phenol injection recently was reported to have successfully blocked refractory pain from metastatic cancer involvement of the abdominal wall (Restrepo-Garces CE, Asenjo JF, Gomez CM, et al. Subcostal transversus abdominus plane phenol injection for abdominal wall cancer pain [published online April 8, 2013]. Pain Pract.
It is important to compound this preparation using strict aseptic technique (see USP <797>).
Precautions: Phenol is corrosive; steps 1 to 3 could be performed in a fume hood and the process moved into the cleanroom at step 4.
No claims are made as to the uses, safety, efficacy, or bioavailability of this preparation; the formulation is for information purposes only.
Mr. Erikson is director of professional affairs and director of professional services at Gallipot, a Fagron company.