According to a new study, kratom could be more toxic to unborn children than morphine.
Researchers at Malaysia's University of Science conducted the study, and it was published online on August 20th, 2021. In it, the researchers evaluated the toxicity of four substances on zebrafish embryos: Kratom, its alkaloids mitragynine and speciociliatine, and morphine.
You might be wondering how zebrafish studies could possibly be relevant to humans. But in the scientific world, the study model is both common and reliable: Zebrafish's genetic similarities to humans allow researchers to accurately emulate and evaluate various substances' developmental effects.
In this case, researchers exposed zebrafish embryos to each substance. They then monitored the embryos for signs of toxicity via various means, such as hatching rate, heart rate, and deformities.
Their findings were staggering: The kratom extract killed 100% of the embryos and decreased their hatching rate at concentrations above 500 μg/ml. Similarly, mitragynine and speciociliatine exposure killed all embryos at 100 μg/ml. But at lesser concentrations, the two alkaloids also caused significant developmental issues: The most prominent was scoliosis, an excessive curvature of the spine.
Morphine had similar consequences, causing deformities of the spine (lordosis) and the heart (pericardial oedema). However, morphine had a significantly lower mortality rate than the tested kratom substances. This led the researchers to conclude that "Altogether, kratom [extract], mitragynine, and speciociliatine at the highest dose display more toxic effects in terms of embryo survival, when compared to morphine."
Zebrafish embryos exposed to kratom decoction, mitragynine, speciociliatine, and morphine. (A) hatching rate at 72 and 96 hpf (hours post-fertilization)
These results have frightening implications for kratom-using pregnant individuals. However, the researchers were quick to highlight their study's limitations. For instance, high concentrations of kratom extract may be lethal to zebrafish embryos but not other species: In one such study, kratom extract doses up to 1,000 mg/kg didn't kill mice test subjects.
Nonetheless, the authors affirmed that kratom use could still pose a significant risk to unborn children. "This finding suggests that the potential risk of kratom intake during pregnancy on the development of the fetus is based on the fact that the early embryo developmental process of zebrafish is similar to humans," they concluded.