In concept, trough to peak (T:P) ratio is a simple and straightforward parameter which succinctly describes the consistency and duration of a drug's antihypertensive effectiveness across its rec- ommended dosage interval.

What does a peak and trough mean?

The trough level is the lowest concentration in the patient's bloodstream, therefore, the specimen should be collected just prior to administration of the drug. The peak level is the highest concentration of a drug in the patient's bloodstream.

When is peak and trough drawn?

A peak drug level is drawn at the time when the medication is being administered and is known to be at the highest level in the bloodstream. A trough level is drawn when the drug is at its lowest in the bloodstream right before the next dose is given.