Supermarkets in New Zealand are able to legally sell paracetamol without any limit on how many packets people can buy at once.
The painkiller has about three million prescriptions written and more than 50 million tablets used each year across New Zealand.
Countdown customers seeking long-term pain relief will now need to be prescribed larger quantities by a GP.
Jeremy Armes, Countdown's head pharmacist, said the supermarket had been looking at how it could sell paracetamol more safely and believed it was best the painkiller was sold in a pharmacy environment where a pharmacist could talk through the risks one-on-one.
"Paracetamol is an incredibly useful and effective medicine but, as with all medicines, it also needs to be respected and treated with care," Armes said.
"There is no doubt that mental health awareness, education and good medical support are going to make the biggest difference for Kiwis suffering with mental illness.
"However, there are also significant and sometimes tragic consequences of overdose, whether that is accidental or intentional."
Armes said anything the supermarket could do to reduce any risks surrounding paracetamol was a good thing.
Where to get help
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call 111.
If you need to talk to someone, the following free helplines operate 24/7: