Monitoring Blood levels

It's all about timing


Some drugs need to be monitored to ensure they are having an optimal effect in the patient. As a results we need to take bloods at a specific time to obtain meaningful information. So when should you make your appointment to measure certain drug levels? We aim to measure trough levels of drugs and this logically occurs just before the next dose is due. However when multiple drugs are given and both need monitoring then the best time is just before the next combo dose, as this will be a dual trough level


PHENOBARBITONE, just before next dose

BROMIDE, just before next dose

PHENOBARBITONE and BROMIDE just before next bromide and phenobarb combo dose

GEMFIBROZIL and BROMIDE just before the next combo dose

THYROXINE just before next due dose

The effect of drugs on blood levels

A related question is when should we measure a biochemical blood level eg glucose, in relation to the administration of a drug that controls it (insulin)? We are trying to measure trough blood glucose levels, so blood sampling occurs at 6 hours post insulin injection. Advice: Client feeds in the morning, injects insulin, and no further feeding until bloods done 6 hrs later

Neomercazoles effect on T4. We are trying to see how low neomercazole drags the T4 level. Usually therefore measure at maximum effect of neomercazole. Neomercazole is ideally given 8 hourly so max effect is about 4 hours after a dose. Thus blood sampling occurs at 4 hours post neomercazole dosing