But after his speech, he told reporters he was just joking.
He said there was "no logic" to Duterte's statement Monday night that he took marijuana to keep up with the grueling schedules during meetings with other heads of states.
"If the President is serious in handling the drug issue, he should stop his tough talk, understand the science behind substance use and addiction, and give the issue the due gravity it deserves", said the Y4MH chair, Dr. Raymond John Naguit.
Shortly after winning the election, Duterte said in several press interviews that he was personally in favor of legalizing medical marijuana.
TRUE to his unique sense of humor, President Duterte sent journalists scrambling once again on Monday following a "joke" that he had used illegal drugs during the Association of Southeast Asian Nations (Asean) Summit in Singapore last month.
He even said children don't watch Duterte's speeches, even when they are aired live on television channels and the internet and are written about by reporters.
Malacañang has a "test" to tell if President Duterte is joking or not.
He added, "That's my style, it's too late to change".
"Medicinal marijuana, yes, because it is really an ingredient of modern medicine" Duterte said.
Rappler CEO Maria Ressa and her company were formally indicted on multiple counts of tax evasion last week, charges critics say are politically motivated and created to silence independent media in the southeast Asian country.
Panelo rejected claims that President Rodrigo R. Duterte himself had a hand at Ressa's arrest warrant since he has repeatedly slammed Rappler for being critical of his war on drugs and other policies.
Panelo also said Duterte had "never" taken marijuana in his life, even though he admitted that he never discussed the matter with the President.
Mr. Pimentel added that it was just a "joke he made up in relation to his story that the schedule he was being required to follow was a punishing one, from 8:30 a.m. up to midnight".
The comment is bound to upset families of the victims of his crackdown on narcotics. Duterte's drug war has killed at least 4,000 people, based on police records but human rights groups allege the fatalities are three times more than that.