Question

Problem 4: you work at a local pharmacy which manufactures and distributes a biomedical device intended to provide a steady state concentration of 16 µg/ml with a infusion rate of 1 mg/hr. As a biomedical engineer, you need to fine-tune your device for a patient with only 1 normal kidney. Calculate the desirable infusion rate for this patient?

Assuming a therapeutic window a 10-20 µg/mL, comment on the condition of the patient if he receives the normal device.

Solution: Infusion rate for the patient: 0.5 mg/hr. If same device is used without dosing considerations, student need to calculate Css and explain what would happen at this plasma concentration.

Answer 1

Patient’s therapeutic window is 10-20 µg/mL which will divide equally to both kidneys. Now the biomedical device likes to provide 16 µg/mL dos which are 8 mg/ml for both kidneys individually. The therapeutic dose is 5-10 µg/mL for one kidney. Therefore, in the absence of one kidney, all drug will move to one kidney. If a patient receives dose more than therapeutic window, it will lead to develop side effects. Here patient is receiving high drug dose (16 µg/mL > 5-10 µg/mL) for a particular kidney.

Therefore, Css rate when the patient receives normal device will be higher because rate of clearance for normal device is higher than desired infusion rate (0.5mg/hr). Therefore, Css value would higher for normal device than the required device.