Bolus Injection
A single, relatively large dose of a drug given as a rapid injection, as opposed to a slow infusion. Bolus injections are used when rapid onset of action is needed. Some peptide drugs, such as glucagon for hypoglycaemia emergencies, are administered as bolus injections.
Technical Context
A bolus injection delivers the entire dose rapidly (typically <1 minute for IV bolus, <30 seconds for SC/IM). This produces a rapid peak concentration (Cmax) followed by distribution and elimination phases. Glucagon emergency treatment for severe hypoglycaemia is administered as a 1mg bolus injection (SC, IM, or IV). Bivalirudin anticoagulation protocol uses an initial IV bolus (0.75mg/kg) followed by continuous infusion. Bolus dosing is appropriate when rapid onset of effect is clinically necessary or when the drug has a short half-life requiring frequent dosing. For peptides with narrow therapeutic windows, bolus administration risks transient supratherapeutic concentrations.