Professor Gordon Parker said the study should act as a “canary in the coal mine” and prompt the Therapeutic Goods Administration (TGA) to urgently investigate.
The study, published in Australasian Psychiatry, analysed six lamotrigine preparations distributed in Australia and two generic versions of the drug used by two patients reporting side effects.
Lamotrigine is an anti-convulsant drug commonly used to treat people with bipolar and epilepsy.
While the analysis of the six preparations were comparable and showed no signs of compromising, the assays of the drugs taken by the two patients showed deviations in the lamotrigine concentration, researchers said.
“The findings are not suggesting that all generics are universally compromised. But our analyses do indicate some compromised lamotrigine medications are being distributed in Australia,” Parker, the lead author of the study, said.
The two patients with bipolar disorder in the study reported bad reactions after taking a generic lamotrigine preparation.
The first developed spots, lumps and blisters following the switch to a generic brand on a low dosage.
The side effects reportedly ceased on return to the non-generic, even at an increased dosage.
The other – who was not previously prescribed lamotrigine – developed breathing issues, chest pain, hot flushes, nausea and a worsening depression on a low dosage.
“It’s not that one particular product is bad, but the generics they were taking seem to be associated with some reasonably toxic side effects, and the irregularities we found from the assays support a faulty batch explanation,” Parker said.
The researchers believe the medication was probably compromised during manufacturing.
“It’s possible that being transported to Australia, they might be exposed to excessive heat or cold and may break down,” Parker said.
“But we suspect there are some manufacturing sites where the product is being compromised or contaminated after receiving TGA approval.”
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In Australia, companies must show evidence of their medications’ pharmacology, efficacy and safety before receiving approval from the TGA.
But pharmaceutical companies may not be aware of manufacturing quality control problems.
“The faulty batches likely reflect some on-site manufacturers having poor quality control processes, and the pharmaceutical companies may be quite unaware of what’s going on with their manufacturers,” Parker said.
According to the TGA, there were 114 adverse events reported for lamotrigine, including four deaths, between January 2018 and February 2021.
Despite this, Parker said the issue is still flying under Australia’s radar.
“This should signal a possible canary in the coal mine phenomena that the TGA should be urgently looking into,” Parker said.