Do we know there is a difference when we take medication orally with food versus when fasted?
In a field known as pharmacokinetics, we measure the drug levels in blood with time.
When we take medication orally, the blood drug concentration will increase to a maximum value (Cmax) at a time, Tmax, during the absorption (A) phase.
Subsequently, the blood drug concentration decreases due to its disposition namely, distribution from blood to tissue (D), metabolism by enzymes (M) and excretion into feces and urine (E).
When we take medication with food, the gastric emptying rate (GER) decreases, the rate of drug absorption in the small intestine decreases and Cmax reduces while Tmax prolongs!
This is logical as it takes a longer time to reach a lower blood drug concentration!
A question arises, will the systemic exposure (area under curve, AUC) increase, decrease or remain unchanged?
The answer: it depends!
- For medication that is highly soluble and permeable, the AUC may not be affected substantially.
- For medication that is poorly soluble, its AUC may even be increased under some circumstances!
As the Cmax and/or AUC is correlated with drug effects, the pharmacological outcome may be different in the presence or absence of food.
Take home message: Food effects on therapeutic outcome can be important for some medications – please adhere to the advice by your pharmacists!
Read also: Pharmacokinetic Service in Hospitals
Resource Person: Eric Chan, PhD