A bolus delivered directly to the veins through an intravenous drip allows a much faster delivery which quickly raises the concentration of the substance in the blood to an effective level. This is typically done at the beginning of a treatment or after a removal of medicine from blood (e.g. through dialysis).

What does bolus mean in medical terms?

Listen to pronunciation. (BOH-lus…) A single dose of a drug or other substance given over a short period of time. It is usually given by infusion or injection into a blood vessel.

What's the difference between bolus and infusion?

The bolus achieves a very high peak which only lasts 5–6 hours. The infusion achieves steady levels after an initial delay. An infusion produces a steady level which can be varied and is exactly what is needed, for example during and after surgery.