All Blacks Cory Jane and Israel Dagg took sleeping pills while they were out drinking ahead of the Rugby World Cup quarter final in 2011, the NZRU has confirmed.
The players were seen drinking, and apparently swaying and slurring their words, at the Mac's Brewbar in Takapuna only 72 hours before the match against Argentina.
New Zealand Rugby Union chief executive Steve Tew has now confirmed sleeping pills, as well as beer, were involved in the incident.
It comes after rugby league players were revealed to be mixing energy drinks and sleeping pills in the week before the Rugby League World Cup semifinal last year.
Tew told media today the issue was dealt with appropriately by team management at the time.
"Those two men made some poor decisions the week of the quarter final. That issue was dealt with by team management," he said.
"I was then and remain comfortable that it was dealt with appropriately.
"We can confirm that there were sleeping pills involved but as I say, at the time it was dealt with we think in the right way and the right context."
Tew said the issue of sleeping pills "wasn't an issue then".
There was no "major red flag" when sleeping pills came up at the time, he said.
"They made some poor decisions, they breached team protocol - they were dealt with and we got on with the World Cup campaign."
Tew said he did not know whether energy drinks were involved in the incident, or how many sleeping pills the players had taken.
The issue at the time was that the players were out past their curfew and had been drinking, he said.
Tew denied there had been a cover-up.
"We did not see sleeping pills then as a big red flag,'' he said.
"We didn't cover anything up. If it happened now, for example, with the issue we have around the use of sleeping pills and energy drinks - well, the apparent issue, because no one yet really understands it - then we would probably take a different course of action.
"At the the time it was not a hot topic.''
Tew said they had not found other instances of players misusing sleeping pills.
The NZRU took any issue that would bring the game into disrepute incredibly seriously, he said.
"We've acted, we think, with a strong zero tolerance policy around supplements, illicit drugs, gambling, alcohol abuse - they're some of the things we deal with, unfortunately, from time to time despite our best endeavours around education and development of our players.''
Tew said there were strong process and procedures in place around prescription drugs. He said sleeping pills were administered by team doctors on an "as-needs and a very scarce basis''.
"But we do play a game that involves a lot of international travel, and for people that travel a lot - long-haul flights, sleeping out of time zones - sleeping pills are used by some people in the clinical sense in that regard.''
The NZRU immediately took stock when the issue became more prominent around the Rugby League World Cup. Tew said some Super Rugby teams had tightened up on the issue.
The NZRU was setting up an integrity unit and research was being undertaken, he said.