Kush, a synthetically made drug that mimics the effects of cannabis, is wreaking havoc among young people in Liberia and neighboring Sierra Leone.
Users of the highly addictive substance are recognizable by their extreme drowsiness and can be seen anywhere from the slums to well-heeled areas.
Boakai said during his 40-minute speech to parliament that he and his vice-president would be the first to undergo a drug test, prompting a standing ovation in the chamber.
"The drug epidemic, especially the use of kush in our country, is an existential threat eating away at the future of our children and the country," Boakai said, adding, "we must stand up and face this national security risk together".
"Given the need for immediate action to make good my pledge to the thousands of families burdened by this crisis, I am hereby declaring drugs and substance abuse as a public health emergency," the president said.
Former president George Weah, who was beaten by Boakai in November's run-off poll, was criticized during the election campaign for failing to take sufficient action to counter the scourge while in office.
Abisseh Dennis, a social worker who helps young people get off drugs in Monrovia, welcomed Boakai's announcement and said he was setting an example for others.
"Where the drug is coming from, they need to stop it from coming into the country," she said, calling for a tougher crackdown on drug traffickers.
Boakai, 79, also pledged on Monday to invest in the country's transport, health and education sectors. He also said his government will fight corruption.
During his inauguration last week, the new president was hit by a brief spell of heat exhaustion and had to pause and sit down to finish his speech.
The scheduled program for the rest of the ceremony was abruptly cut short because of the incident.
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