Understanding the Concept:
Sterile injections of lipophilic steroid hormones, such as progesterone, require a non-aqueous vehicle to completely dissolve the therapeutic dose. The choice of vehicle is governed by compendial monographs to ensure stability, safety, and appropriate viscosity.
Monograph Analysis:
• According to official British Pharmacopoeia (BP) monographs for Progesterone Injection, the formulation is defined as a sterile solution of Progesterone in a suitable fixed oil or ester vehicle.
• While fixed vegetable oils (such as arachis oil or sesame oil) are commonly used, the BP monograph specifically identifies Ethyl oleate as a preferred fatty acid ester vehicle for this injection formulation.
• Ethyl oleate provides lower viscosity than many natural vegetable oils, resulting in easier syringeability and reduced pain at the intramuscular injection site.
Thus, option (B) represents the specified vehicle under these compendial standards.