Composition and Labelling Accuracy of Products Sold as Retatrutide in Australia

1. Introduction

Retatrutide is an investigational triple glucagon‐like peptide‐1, glucose‐dependent insulinotropic polypeptide and glucagon receptor agonist currently undergoing clinical evaluation for obesity treatment [1]. Despite not being approved for therapeutic use in Australia or internationally, products marketed as retatrutide are increasingly available through online peptide vendors and informal supply networks [2]. These products are increasingly marketed directly to consumers via social media platforms. This promotion pushes glucagon‐like peptide‐1 demand beyond clinical obesity populations to younger people with no clinical need, who seek body‐composition and enhancement effects on the basis of supplier claims that cannot be independently verified. Recent Australian media reports have highlighted severe adverse events associated with purported retatrutide use, including acute liver failure [3]. However, little is known about the composition of products being sold as retatrutide within Australia. We analysed samples submitted to PEDTest Australia, a community‐facing private drug analysis service, to determine whether products marketed as retatrutide contained the expected peptide and labelled dose.

2. Methods

Three products sold as retatrutide and labelled as containing 10 mg were anonymously submitted to PEDTest Australia, a community‐facing private drug analysis service that also provides independent chemical analysis of consumer‐submitted products. Samples were analysed by an independent National Association of Testing Authorities‐accredited laboratory. Peptide identity was confirmed using molecular weight analysis. Peptide content was quantified to estimate the amount of retatrutide present in each vial. Additional testing for metals and inorganic contaminants was undertaken using inductively coupled plasma mass spectrometry and associated analytical methods. These methods have been reported on previously [4].

3. Results

The three samples contained retatrutide, with measured molecular weights closely matching the expected molecular weight of authentic retatrutide (4730.477 Da). However, substantial variation was observed in peptide content (Table 1). One product contained 5.13 mg of retatrutide (51.3% of labelled content), while the remaining products contained 16.5 mg (165.0%) and 19.0 mg (190.0%), respectively. Thus, measured peptide content ranged from approximately half to almost double the labelled dose.

TABLE 1.

Presence and purity testing results.

Sample	Label claim	Retatrutide detected (mg)	% of labelled content
1	10 mg	5.13 mg	51.30%
2	10 mg	19.0 mg	190.00%
3	10 mg	16.5 mg	165.00%

Note: Values represent measured peptide content in samples labelled as 10 mg retatrutide. Percentage of labelled content was calculated as (measured amount/10 mg) × 100.

Heavy metal and elemental impurity analysis identified no arsenic, cadmium, chromium, nickel or mercury above analytical quantitation limits (Table 2). Lead was detected at 0.7 mg/kg, exceeding the practical quantitation limit (0.6 mg/kg). Copper and zinc were also detected at 0.9 mg/kg and 3.7 mg/kg, respectively. When interpreted using Therapeutic Goods Administration/ICH Q3D elemental impurity guidance for pharmaceutical products [5, 6], all detected elemental concentrations were low and substantially below toxicologically relevant exposure thresholds for injectable products.

TABLE 2.

Heavy metal testing results.

Element	Result (mg/kg)	Estimated exposure per 10 mg vial (μg/day)	PDE (μg/day, injectable)	% of PDE	Interpretation
Arsenic (As)	< 0.6	< 0.006	15	< 0.04%	Not detected (below PQL)
Cadmium (Cd)	< 0.1	< 0.001	2	< 0.05%	Not detected (below PQL)
Chromium (Cr)	< 0.6	< 0.006	10	< 0.06%	Not detected (below PQL)
Nickel (Ni)	< 0.6	< 0.006	20	< 0.03%	Not detected (below PQL)
Mercury (Hg)	< 0.02	< 0.0002	3	< 0.01%	Not detected (below PQL)
Lead (Pb)	0.7	0.007	5	0.14%	Detected
Copper (Cu)	0.9	0.009	Not primary ICH Q3D element	—	Detected
Zinc (Zn)	3.7	0.037	Not primary ICH Q3D element	—	Detected

Note: Estimated exposure per 10 mg vial was calculated by converting measured concentrations (mg/kg) to absolute mass per 10 mg product. Permitted daily exposure (PDE) limits are based on ICH Q3D guidance for elemental impurities in parenteral medicines, as adopted in Therapeutic Goods Administration Good Manufacturing Practice frameworks. Copper and zinc are not primary ICH Q3D elemental toxicity targets and are included for completeness due to physiological relevance. Values reported as “<” indicate concentrations below the practical quantitation limit (PQL).

4. Discussion

In this small analysis of products sold as retatrutide in Australia, all samples contained the expected peptide, but the quantity present varied substantially from the labelled content. The observed variability raises concerns regarding dose accuracy and product quality within unregulated peptide markets.

When contextualised against ICH Q3D/Therapeutic Goods Administration permitted daily exposure limits, detected elemental impurities were well below toxicologically relevant thresholds. Lead was present at trace levels (0.007 μg per 10 mg vial; 0.14% of permitted daily exposure), with copper and zinc detected at low concentrations consistent with physiological exposure ranges.

These findings are particularly relevant given growing consumer demand for injectable peptides [7] and increasing reports of adverse events associated with peptide use in Australia [3]. Although media attention has often focused on counterfeit or adulterated products, these findings suggest that inaccurate dosing alone may represent an important source of risk. Individuals purchasing products marketed as retatrutide may unknowingly administer substantially lower or higher doses than intended.

Notably, only three samples were analysed, and the findings may not reflect the broader illicit peptide market. However, the dosing inaccuracy observed here is consistent with the uncertainty about product contents, dosing, and supply‐chain quality repeatedly documented across self‐reported and chemically verified studies of people who use unregulated enhancement drugs, suggesting these results are unlikely to be anomalous.

Sterility and endotoxin contamination were not assessed, and this is an important area to explore in future work. Nevertheless, these findings provide, to our knowledge, the first published empirical data describing the chemical composition of products marketed as retatrutide from illicit markets. As consumer demand and direct‐to‐consumer marketing for injectable peptides expand, the problem of unreliable vial contents is likely to grow in the absence of regulation, highlighting the value of community‐facing drug analysis services and surveillance systems for identifying emerging drug‐use risks related to peptides.

Author Contributions

T.P.: conceptualisation, investigation, resources, data curation, writing – original draft, writing – review and editing. A.C.: conceptualisation, resources, project administration, writing – review and editing. S.C.: writing – review and editing. J.F.: supervision, writing – review and editing.

Funding

T.P. receives support from a National Health and Medical Research Centre Investigator Grant (2041822) and funding from the Queensland Mental Health Commission and Alcohol and Drug Foundation. He has received funding from Hyphen Health, Queensland Injectors Health Network, and Queensland Injectors Voice for Advocacy and Action. A.C. is the CEO of PEDTest Australia, a private harm reduction and enhancement drug testing company.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.