American Podiatric Medical Licensing Examination (APMLE) Part 1 Practice Test

Protamine zinc insulin is formulated to slow how quickly insulin is absorbed from the injection site. The protamine binds the insulin, and the zinc helps stabilize the insulin complex, creating a depot that releases insulin slowly over time. This results in a longer duration of action compared with regular, faster-absorbing insulins. It doesn’t have immediate onset, isn’t given orally, and isn’t a short-acting preparation, so the description that best fits is a prolonged duration due to the presence of protamine and zinc.