Metro Manila (CNN Philippines) — Presumptive president Rodrigo Duterte on Monday (May 23) said he would not allow the legalization of marijuana, but he supports the use of medical marijuana.

“Medicinal marijuana – yes, because it is really an ingredient of modern medicine now,” Duterte told reporters. “There are medicines right now being developed or already in the market that contains marijuana as a component.”

Duterte said he has seen its ill effects during his youth when his friends got high on marijuana.

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The U.S. Food and Drug Administration has not yet approved marijuana plant as medicine, but at least 24 states have legalized it for medical use.

Various scientific studies say that marijuana plant contains chemicals that aid in the treatment of a number of diseases and symptoms — reasons cited by a growing number of people who argue that it should be legalized for medical purposes.

Scientists have developed medicines using the plant’s oil to treat certain conditions such as childhood epilepsy. According to studies, marijuana extracts have also been proven useful in reducing pain and inflammation and controlling epileptic seizures.

U.S.-based National Institute on Drug Abuse says preclinical and clinical trials are being conducted, using marijuana and its extracts to treat numerous diseases and conditions, such as HIV/AIDS, multiple sclerosis, Alzheimer’s disease, mental illness and even addictions.

Marijuana remains illegal in the Philippines. Anybody caught possessing or using marijuana even for medical purposes may be sentenced to years in jail or life imprisonment.

CNN Philippines' Ina Andolong contributed to this report.