Police say three teenagers have been charged over abducting the same man twice in Sydney in the past week.

Investigators say a 19-year-old was drugged while being held against his will at a motel in Chullora in the city's south-west on Friday night.

Officers say a trio had earlier put him into a car and taken him to the motel where he was forced to take sleeping tablets.

Detectives say he managed to lock himself in a bathroom and call police.

A 19-year-old, an 18-year-old and a 17-year-old were arrested over the kidnapping and taken to a local police station to be questioned.

Detectives allege the trio had also abducted the same man from a park last Sunday and assaulted and robbed him.

The teenagers have been charged with 35 offences.

They have been held in custody and are to face court today.