At best patients will be wasting their money, and there are risks to prescribers too, experts warn.
Experts have warned against the practice of microdosing GLP-1 receptor agonists to make a single injector pen last longer, saying patients risk losing clinical benefits, compromising the stability of the medication and wasting their money.
Many patients have reportedly reacted to the cost of the popular weight-loss drugs by shrinking their doses to extend the lifespan of one GLP-1 injector.
But patients who microdose or “click-count” and use a pen device for two months rather than one are doing so “outside the recommendations of safe and effective use of medications”, said Dr Terri-Lynne South, chair of the RACGP’s obesity management specific interest group.
Dr South said microdosing to extend the lifespan of one GLP-1 pen was “definitely” happening in Australia and was absolutely off-label use.
“There are theoretical risks in regards to stability, shelf life and effectiveness of the medication if it’s used outside what has been a registered therapeutic device and use of medication,” she said.
“And if people are doing this without the recommendations of a healthcare professional, the concern is that they’re not actually getting what they need clinically.”
Dr South noted that there was a “huge variability in clinical response” among different patients to GLP-1 medications.
“Some people can still have significant clinical response, whether that’s weight loss or cardiometabolic risk factor reductions, at lower doses than what has been shown in the trials or promoted as TGA recommendations of prescriptions.
“If an individual prescriber is saying, ‘Hey, you don’t need to go up on your Mounjaro because you’re having a fantastic clinical response’, that’s within normal prescribing guidelines and is supported.”
But Dr South said that was an entirely different situation to a patient independently deciding that they want to have a very small dose for weight management.
“I don’t recommend it. If someone came to me and told me what they were doing, as a healthcare professional it’s about harm minimisation, and for that patient in front of me to understand what the pros, cons and risks are in that respect.
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“In some clinical situations, I might agree that they don’t need a higher dose for what they’re trying to achieve, but I wouldn’t be recommending that people are trying to get more medication out of their device outside those recommendations.”
Dr South said clinicians needed to be aware of the potential medicolegal risks if they continued to prescribe GLP-1s knowing that patients were taking lower doses than recommended.
“I think there can be some medicolegal risks around a prescriber who willingly is prescribing a greater dose than what the patient is taking in order to manipulate the pen devices, but that’s a very different clinical situation to prescribing lower doses that are still having an appropriate therapeutic effect.”
Dr Gary Deed, chair of the RACGP’s diabetes specific interest group, said microdosing “flies against the evidence of the efficacy trials”.
“The indications not only show the efficacy and the type of patients you should use it on, but also the doses that have been proven.”
Dr Deed said microdosing was not scientifically validated. “Basically, you’re addressing cost rather than the clinical condition for which it’s indicated.”
There was no evidence that microdosing had non-glycaemic or cardiovascular benefits in overweight or obesity or people with cardiovascular disease, he said.
“The clinical benefits of these classes in emerging studies have not been validated at microdosing.”
Dr Deed said the “least harmful outcome” for patients would be a waste of money.
“The risk is that you’re financially impairing yourself for minimum benefit and outcome and exposing yourself to side effects without any benefits.
“When we use any medication, we’re balancing the risk versus benefits, or risk versus efficacy. And if you’re going to reduce the efficacy by using inappropriately low doses, you reduce the risk-benefit ratio, and you’re having to still pay some considerable amount of money to obtain the medications.
“It may emerge over time that studies may support this, but currently, as they’re indicated in the Australian environment, there isn’t evidence to support people microdosing.
“We certainly wouldn’t start a microdosing of medications unless there was some extraordinary indication for it, but that would be under a specialist or clinical trial situation.”
