The couple, who cannot be named, both worked for the Wairarapa District Health Board.
According to the police summary of facts, the theft was discovered when the health board realised usage of the drug had increased and began auditing who accessed the restricted part of the hospital.
Its monitoring showed the man had used his swipe card to access the restricted area.
He was arrested in September, after he was seen pocketing a vial of the drug.
Mr Elliott said any conviction for dishonesty would be "catastrophic" for the pair's future employment.
The offending had taken place when both were at their lowest ebb, Mr Elliott said.
The woman had been suffering from a major depressive illness and a workplace injury, he said.
"This offending was not motivated, as would normally be seen by the court, by any monetary greed."
She had received poor treatment for her condition and had lost 24 per cent of her body weight due to the stress she was under.
She had also recently left an abusive relationship, Mr Elliott said.
The man was also under pressure, having recently been through a marriage breakup.
"[He was] watching his partner in acute distress and receiving ineffective treatment which was poorly managed, and it was at that stage the catastrophic decision was made.
"At his lowest ebb, one can sympathise with the very special brand of hopelessness that [he] must've felt, slipping into that abyss."
The pair had been allowed to resign from their jobs and had independently advised their professional bodies of the offending. The man had suffered significant financial losses, Mr Elliott said.
"[He's] unable to provide for his children, selling assets and vehicles and various insurance policies."
The pair had shown "remorse, shame and regret" and had entered early guilty pleas. Mr Elliott said the pair were willing to pay full reparation if ordered to by the court.
Police prosecutor Jodie Lawrence said a "weight needs to be put on the gravity of the offending".
"The fact that they've taken from their employer a dangerous drug and the premeditated and ongoing nature of the offending should be of concern to the public," Ms Lawrence said. "Medical professionals can't be seen to be getting away with taking or stealing drugs."
A conviction without discharge was not sufficient, she said.
Judge Barbara Morris has reserved her decision until later this month.