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Prescribing phentermine

MPS medicolegal consultant Dr Aine McCoy says that doctors who prescribe phentermine (duromine) for weight control should ensure that they comply with good prescribing practice, to avoid having to justify their practice to the Medical Council

Phentermine has been used for weight reduction for many years in New Zealand. It is chemically related to amphetamine, with major effects upon the dopaminergic and noradrenergic systems. These include appetite suppression, increased heart-rate and force of contraction, gastrointestinal side effects and general central nervous system stimulation – particularly mood changes. Rarely it can cause psychotic symptoms.1

As phentermine is similar to amphetamine, it is a controlled drug (class C5) and has the potential for abuse. Duromine is not funded by Pharmac, so patients pay $160-$200 per month when they present a standard prescription of 30mg daily – in addition to the GP consultation fee.

However, the medication does have a considerable street value. The Medicines Control section of the Ministry of Health (which is responsible for containment of drug abuse) carries out regular surveys of pharmacies nationwide to ascertain the number of phentermine prescriptions dispensed and to check on GP prescribing patterns. Where their investigations reveal cause for concern they may report the doctor to the Medical Council for further investigation.

Other ways of a doctor coming to the notice of the Medical Council include notifications by pharmacists and other medical or nursing colleagues. Patients rarely complain.

The data sheet for duromine advises that it should only be used as a short-term adjunct in obese patients (defined as those with Body Mass Index (BMI) >30) where a comprehensive regime of weight reduction, which includes exercise, dietary and behaviour modification, has not achieved an adequate clinical response. Some patients whose BMI is <30 might also use it where they have other relevant medical conditions. 

As part of their investigations, the Medical Council will ask the doctor to provide patient notes. Some common problems found in the patient notes, which can lead to concerns and possible disciplinary action by authorities such as the Medical Council, include:

  • Lack of documentation about previous weight reduction regimens
  • Lack of documentation of height, weight (BMI), recent pulse and blood pressure measurement
  • BMI not >30, or no relevant medical problems existing where it has been used in patients with a BMI <30

The Medical Council guideline on Prescribing Drugs of Abuse (April 2010)2 states that it is unethical to provide any treatment that is illegal or detrimental to the health of the patient. The Medical Council defines “improper over-prescribing of drugs of abuse” as any prescribing of drugs of abuse that deviates significantly from the practice of one’s medical peers.

If a doctor believes that a patient is addicted to medication, then they should first take steps to ensure patient safety
Such prescribing practice may include indiscriminate, excessive or reckless prescribing. The Council also states that “the Council is provided with the jurisdiction to inquire into the prescribing of any doctor for the purpose of considering and determining whether the said doctor is prescribing inappropriately. If the Council concludes that a doctor is prescribing inappropriately it may recommend to the Minister of Health that the doctor be prohibited from prescribing all, or specific classes of prescription medicines.”

The Council can also order a competence review of the doctor or, in more serious cases, the doctor can appear in front of the Health Practitioner’s Disciplinary Tribunal, where a finding of professional misconduct will result in penalties, which include a fine up to $3,000, having to practise under supervision or having their registration suspended or cancelled.

If a doctor believes that a patient is addicted to medication, then they should first take steps to ensure patient safety. Information and assistance can also be sought from Medicines Control to check if the patient is obtaining prescriptions for similar medications from other doctors or is listed as having a Restriction Notice. They can be contacted on Wellington 0800163060 or Auckland 0800248671.


2. MCNZ, Prescribing Drugs of Abuse (April 2010)

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