Describe the different types of half-life and their importance regarding substance use.

Distribution half-life is the amount of time it takes for a substance to enter circulation. This is a critical issue for medications involved with pain management as the patient and physician wants the medication to start controlling pain as quickly as possible. Distribution half-life has two components. The alpha half-life is the period after peak blood concentrations for the substance whereas the beta half-life is the time frame before the substance concentration in the system begins to decline. Regarding benzodiazepines, the beta half-life plays a role in where the drug is a short, medium, or long-acting benzodiazepine. Therapeutic half-life is the time to inactivate 50% of the substance whereas the elimination half-life is the time to eliminate 50% of a single dose of a substance from the body.