This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Pharmacology, Subject name: Pharmacology
What instruction do you give to a mother who is lactating regarding intake of drug? 
Select and explain. 
A. No advice as most of drug are not secreted into breast milk, B. Give longer half-life drugs, C. Tell the mother to feed when it is least efficacious, D. Lactate Just before she take the next dose, when the plasma concentration of drug would be least.
D: Lactate Just before she take the next dose, when the plasma concentration of drug would be least.
Answer: D: Lactate Just before she take the next dose, when the plasma concentration of drug would be least. 
Explanation: ANS. DPlasma concentration of drug varies with time follows the graph as shown below. Certain drugs can be secreted in breast milk and therefore transferred to the infant. Care should be taken to decrease this to the minimum possible levels.Least plasma concentration of the drug will be just before the next loading dose. Hence, the least chance for the drug to be concentrated in milk and thereby transferred to the infant would be at the time just before taking next dose. Hence advice mother to lactate just before taking next dosage of the drug.