Phenols parenteral preparations

Almond oil is used therapeutically as an emollient and to soften ear wax. As a pharmaceutical excipient it is employed as a vehicle in parenteral preparations, such as oily phenol injection. It is also used in nasal spray,and topical preparations. Almond oil is also consumed as a food substance, see Section 18. 

Phenol is up to 7 % soluble in water. The active concentration is 0.5 %. It is used as a preservative in parenteral preparations and exceptionally in cutaneous preparations, because of the unpleasant smell. 

Corticosteroid sodium phosphate salts used in parenteral preparations, i.e., eye, and ear drops, have been separated by reversed phase ion pair chromatography on silanized silica gel stationary phase, using aqueous triethylamine-methanol (3 2, v/v, pH s 4.2) as mobile 4tase. The separated spots were assayed by densitometry at a wavelength of 240 nm (73). Sodium phosphate salts of betamethasone, dexamethasone, and prednisolone have been quantitatively determined in the presence of chloramphenicol in eye and ear drops, also methyl and propyl parabens, and phenols. 

The need for a multidose formulation may also dictate the use of a solid-state formulation. As the name implies, multidose products are intended to provide the patient with a product that contains several doses of the therapeutic within one container. Multidose formulations contain preservatives to kill any bacteria and prevent mold growth that may result from repeated entry into the drug product. Phenol and benzyl alcohol are two widely used preservatives in protein-based parenteral pharmaceuticals. Frequently, the addition of a preservative to the formulation compromises the long-term stability of the drug product, typically because the protein becomes physically unstable and/or exhibits oxidation. If the formulation scientist can obtain sufficient short-term stability (e.g., 2 weeks) for a formulation containing a preservative, then the use of a solid-state product may enable production of a multiuse formulation. In this case, the preservative is NOT added to the liquid bulk used to prepare the solid state. Instead, when the solid-state formulation is reconstituted prior to use, a preservative is included in the water for reconstitution. Thus the final product to be used is a multidose formulation that will experience only short-term exposure to the preservative. 

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