Why should drugs administered by injection not be stored in syringes for prolonged periods?

Drugs should not be stored in syringes for prolonged periods primarily because the plastic syringe may absorb the drug. Many medications can interact with plastic materials, leading to a decreased concentration of the drug due to sorption, which is the adhesion of drug molecules to the surface of the syringe. This effect can significantly alter the potency and effectiveness of the medication when it is finally administered.

In addition, storing drugs in syringes for extended periods poses risks associated with stability and sterility. While concerns like needle corrosion, drug crystallization, and the plunger sticking could arise under certain conditions, they are not the primary reasons for avoiding prolonged storage in syringes. Maintaining the integrity of the drug and ensuring accurate dosing are crucial, which is why it's best to draw medications into syringes just before administration.