Human rights lawyer Haron Ndubi was arrested Sunday night for driving while drunk, police have said.
But human rights activists say he was drugged and arrested while in critical condition.
But Nairobi police boss Japheth Koome disputed that Mr Ndubi was drugged.
He told the Nation on Monday that Mr Ndubi was arrested at 8.45pm on Jakaya Kikwete Road.
“He parked the vehicle in the middle of the road…he slept in the vehicle…[he was] very drunk,” Mr Koome said.
“He was arrested. He is in custody, and he is going to court this morning for driving under the influence of alcohol.”
On Sunday night, activist Alamin Kimathi tweeted that Mr Ndubi was drugged near State House and police arrested him “instead of taking him to hospital”.
He said the lawyer was “in critical condition at Kileleshwa Police Station”.
Mr Koome did not confirm in which police station the lawyer was being held, but maintained the lawyer was not drugged.
He added that Mr Ndubi was conscious.