A security guard was hospitalised after an alleged intruder at a residential complex in Johannesburg forced him to smoke a substance that left him disoriented, paramedics said on Tuesday.

"He became completely incoherent and was not even able to stand up or hold his head up straight," Netcare 911 spokesman Mark Stokoe said.

The alleged intruder allegedly attacked the security guard at a Northworld complex at around 9.30pm on Monday and threatened to kill him when he refused to smoke the unknown substance.

"Once he smoked the substance, he was forced into a clump of bushes just next to the gate. He however managed to push the panic button and back up was there very quickly," said Stokoe.

When back-up security guards arrived at the complex, the alleged intruder had already gone but the attacked security guard managed to relate the incident before he became incoherent.

Paramedics called to the scene took him to the Netcare Olivedale clinic for further treatment.

"Despite his condition being somewhat concerning, it was fortunately not thought to be life-threatening," he said.

He said they were still awaiting results of blood samples taken to determine the nature of the substance the guard was made to smoke.