St George Illawarra, Newcastle and Gold Coast face fines totalling $350,000 as the NRL launches a major clampdown on alleged breaches of concussion protocols.

The Dragons were slugged with a $100,000 fine after Josh Dugan appeared to cop a head knock in Sunday's win over Cronulla but was allowed to play on.

The Knights were slugged for the same amount after Brendan Elliot stayed on after copping a swinging arm from Hymel Hunt while the Titans are facing a $150,000-sanction over the treatment of Kane Elgey, Joe Greenwood and Ryan Simpkins.

The clubs have five days to respond to the breach notices.

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"These are, by far, the heaviest fines ever proposed by the game for concussion breaches," NRL CEO Todd Greenberg said.

"That is how seriously we take it.

"The clubs involved have the opportunity to respond to the Breach Notices, and we will consider those responses, but our message is clear ... we are not going to allow player safety to be put at risk through breaches of the concussion rules."

Greenberg said the NRL had put significant resources into concussion training and education.

"In the majority of cases we see strong compliance with the League's concussion rules but it appears that this did not happen at the weekend in some matches and we cannot stand by and allow player safety to be put at risk," he said.

The Dragons earlier defended the decision to allow Dugan to stay on the field, saying the incident had nothing to do with concussion.

"I think it was a jaw injury not a head injury, that's the report I got back in the box," Dragons mentor Paul McGregor said.

Play was stopped for at least a minute when Dugan lay motionless on the turf copping a stray elbow from teammate Russell Packer, but the Dragons No.1 was allowed to play the next 71 minutes.

The Knights allowed fullback Elliot to play the rest of the game despite suffering a head knock in the 28th minute of their loss to South Sydney.

- AAP