According to Zakharova, the diplomat was assigned to buy the expensive medication that cost $10,000 and was essential for Primakov's treatment, after he received the corresponding money transfer from Russia.
The spokeswoman stressed that all formal requirements were fulfilled, including necessary health certificates and medical prescriptions.
But just as the diplomat was entering the pharmacy, he was approached by US intelligence officers who escorted him to the basement of the shop and "talked to him" for about an hour.
"The things they said to him resembled an attempt to recruit him, rather than any adequate discussion," Zakharova said.
As a result, the medication was confiscated and the money was not returned. Although Zakharova noted that US Secretary of State John Kerry called the situation unacceptable and made every effort to deliver the medication to Russia, "it took a lot of time" and "it was too late," Zakharova said.
Despite Kerry's intervention in the situation, the Russian diplomat was ordered to leave the United States.
Yevgeny Primakov, who was the head of the Russian government in 1998-, died in June 2015 of liver cancer.