It is not surprising this energetic 75-year-old cannot remember when he retired.
He is busier than ever, pursuing his passion for medicine safety, or what he calls the "Cinderella" specialty, pharmacovigilance.
Recently, he was awarded honorary membership of the International Society of Pharmacovigilance in appreciation of his "pioneering and enduring contributions to the development and philosophy of pharmacovigilance and therefore to the safer use of medicines for humanity".
One of Dr Coulter's tasks in his retirement from the University of Otago (which he thinks may have been about three years ago) has been voluntary work with the World Health Organisation (WHO) to help set up medicine safety monitoring programmes, known as cohort event monitoring, in African countries.
Malaria, which Dr Coulter said killed a person every six seconds, was a huge problem in such countries - much bigger than Aids.
Pregnant women and children were particularly susceptible and there was a need for a medicine which was effective and safe for pregnant women.
It was important that any drugs were monitored properly, not only for the sake of safety but because programmes could be exposed to media scares about safety which might not be based on fact and which could ruin valuable programmes.
He cited the case of a scare about a worm medication in Ghana where mayhem ensued after a report of a child dying after taking the drug.
Investigation revealed the child had died because a brick wall had fallen on him.
Dr Coulter believes his early experience in the 1960s in the New Hebrides - now Vanuatu - helped him develop adaptable programmes.
In Tanzania, for instance, he was surprised to discover, after talking to local people, the most effective way to get information on adverse events was to contact patients by cellphone.
Many did not have mailing addresses or landline telephones, "but nearly everyone has a cellphone".
New Zealand is regarded as a world leader in pharmacovigilance and it was Dr Coulter's involvement with the intensive medicines monitor-ing programme in Dunedin from its commencement which led to his current work.
Dr Coulter sees his work as a career which has come full circle.
"It's been quite a help to have that background in treating malaria, even though it was a long time ago. I understand a lot of the problems, having lived in a developing country. I understand some of the cultural differences."
Identifying patients was one of the difficulties faced in such countries.
Patients could give different names depending on who they were talking to or, if they did not know their birth date, could claim to be 90 "when they were nowhere near it".
When he returned to Dunedin after 10 years in the New Hebrides, Dr Coulter worked as a general practitioner, but he wanted to have another part-time interest, so he offered his services to the medical school.
After a couple of years, he was contacted by Prof Garth McQueen about the possibility of work in establishing a new programme monitoring medicine safety.
What started out as a half a day per week in 1977 gradually increased to full-time work and, eventually, the national pharmacovigilance centre was established.
Dr Coulter is keen to emphasise the limits of randomised controlled trials when it comes to safety.
People assumed just because a drug had come through a randomised controlled trial in its development that "we will know all we need to know about its safety. That's a complete myth."
Dr Coulter said the spontaneous reporting of adverse reactions, either by doctors or patients, did not provide information quickly enough about problems which might be occurring, so it was necessary to ask doctors prescribing a particular drug to answer much more detailed questions about patients taking the medicine.
It is estimated about 10,000 to 15,000 patients are sufficient to identify whether there are problems with a drug.
The information from such a sample could be analysed and doctors advised more fully about suitable prescribing practice.
But while everyone agreed medicines should be monitored, the importance of the procedure was still not fully recognised and adequately funded.
Dr Coulter said there were several studies which showed the impact of adverse reactions on patients and the corresponding cost to the health system.
One study in the United Kingdom found that 6.5% of all admissions to hospital were due to adverse reactions to medicines and the cost of the cases was estimated to be the same as running seven 800-bed hospitals.
In addition to those people admitted to hospitals, it was also estimated that a further 6% had their stays lengthened because of adverse reactions in hospital.
In the United States, a study estimated adverse reactions to medicine were ranked in the top six causes of death.
Although not all adverse reactions could be avoided, it was estimated that between 50% and 60% could be prevented if doctors were made aware of prescribing problems.
As well as his work helping other countries develop monitoring programmes, Dr Coulter is one of 12 members of the WHO advisory committee on the safety of medicinal products who meet annually to advise the organisation on issues.
He has published a variety of works in connection with his WHO work, including guidelines on the safety monitoring of herbal medicines in pharmacovigilance systems and helped with two papers published in China on contraceptive medicines.
Real retirement is something Dr Coulter has not thought too much about yet.
He said that while he was fit and able he would like to continue as long as he was thought "useful" - at least as long as it took to get the cohort event monitoring programmes running independently.
Adverse drug reactions
Unintended, harmful reactions to medicines (known as adverse drug reactions) are among the leading causes of death in many countries.
•The majority of adverse drug reactions (ADR) are preventable.
•People in every country are affected by ADRs.
•In some countries, ADR-related costs, such as hospitalisation, surgery and lost productivity, exceed the cost of the medications.
•No medicine is risk-free. Vigilant assessment of the risks and benefits of medicines promotes patient safety.
Reactions can be prevented. At least 60% of ADRs are preventable, and can be due to:
•Wrong diagnosis of the patient's condition.
•Prescription of the wrong drug or wrong dosage of the right drug.
•An undetected medical, genetic or allergic condition that might cause a patient reaction.
•Self-medication with prescription medicines.
•Not following the instructions for taking the medication.
•Reactions with other drugs (including traditional medicines) and certain foods.
•Use of a substandard medication whose composition and ingredients do not meet the correct scientific requirements, and can be ineffective and often dangerous.
•Use of counterfeit medicines with no active ingredients or the wrong ingredients, which can be dangerous or fatal.
Source: World Health Organisation
