The drug agency also seized 1.08 million kg of drugs from 4,000 people.
The National Drug Law Enforcement Agency said it arrested 4,241 persons for drug-related offences in the first half of 2012.
The Head of Public Affairs of the agency, Mitchell Ofoyeju, said on Friday that the figure is the total arrests made in the 36 states and Abuja.
Mr. Ofoyeju said that 3,979 of those arrested were male, while 262 were female.
He said that 1.08 million kilograms of drugs were also confiscated from drug traffickers during the period.
According to Mr. Ofoyeju, the drugs include 50,294 kg of cannabis, 149,399 kg of heroin, 58,026 kg of cocaine,; and 823,877 kg of psychotropic substances.
The drug agency spokesman said that 978 of the 4,241 persons arrested have been convicted and are serving jail terms.
“The reason why more people are yet to be convicted is because the courts are on recess,” Mr. Ofoyeju said.
“Once the courts are back in session, the other cases in court would be tried,’’ he said.