Dexamethasone absorption from the injection site depends heavily on factors like the formulation (e. g., suspension vs. solution), injection site blood flow, and the drug’s concentration. Solutions generally absorb faster than suspensions. Intramuscular (IM) injections typically result in slower absorption than intravenous (IV) administration, with peak plasma concentrations appearing within 1-3 hours after IM injection. Subcutaneous (SC) injections offer even slower absorption profiles.
Factors influencing absorption
Proper injection technique significantly influences absorption. For instance, injecting into a well-perfused muscle mass promotes faster absorption compared to sites with poor blood supply. Furthermore, factors such as patient age, body composition, and the presence of any inflammation or scarring at the injection site affect drug distribution.
Distribution and Metabolism
Once absorbed, dexamethasone distributes throughout the body, readily crossing the blood-brain barrier. Its distribution is influenced by plasma protein binding; approximately 77% binds to plasma proteins. Metabolism primarily occurs in the liver, with metabolites then excreted by the kidneys. The elimination half-life is approximately 3-5 hours.
