Fact check: Do inactive ingredients in ivermectin tablets vary by manufacturer?

1. Why manufacturers can and do use different inactive ingredients — the technical reality that matters

Pharmaceutical manufacturers routinely select excipients — binders, fillers, disintegrants, lubricants, antioxidants — to achieve tablet stability, manufacturability, and desired release characteristics; regulatory module disclosures show ivermectin tablets using microcrystalline cellulose, pregelatinized starch, magnesium stearate, butyl hydroxy anisole, and citric acid in at least one product dossier, demonstrating legitimate formulation variation across manufacturers ^[1]. Differences also arise when companies develop novel delivery systems, such as lyophilized dry emulsions intended to improve bioavailability; these innovations necessarily change the palette of inactive ingredients used in the final tablet ^[5]. This technical diversity is expected and consistent with regulatory frameworks that allow multiple excipient options provided safety and performance are demonstrated ^{[1] [5]}.

2. Analytical studies show formulation variability and raise quality flags

Qualitative analyses of market samples in South Africa and seizures during the COVID-19 period reveal variation and serious quality concerns, including undeclared active pharmaceutical ingredients and noncompliance with quality criteria, which imply more than simple excipient differences — they point to potential falsification or contamination ^{[2] [3]}. The South African analysis found multiple formulations contained at least one undeclared active ingredient, suggesting that some products on the market differ substantially from their labels and that inactive composition differences may accompany other, more hazardous deviations ^[2]. Seizure-motivated testing found none of 19 samples compliant, indicating variability often correlated with poor manufacturing or supply-chain issues ^[3].

3. Pharmacokinetic studies and formulation research imply functional differences from excipient choices

Comparative studies of systemic availability for ivermectin administered as different formulations — tablets, solutions, capsules — demonstrate that formulation choices, including excipients, affect absorption and bioavailability, even when the declared active ingredient is the same ^[4]. Research into optimized dosage forms, like the 2025 lyophilized dry emulsion work, specifically targets excipient and process changes to alter oral delivery, reinforcing that inactive ingredients are not inert in function and that manufacturers’ choices can yield clinically meaningful differences ^{[5] [4]}. This underscores why regulators evaluate formulation composition, not only active content.

4. Regulatory and safety literature provide limited direct cross-manufacturer comparisons

Residue monographs and clinical safety reviews of ivermectin primarily address toxicology, safety profile, and residue limits rather than itemized excipient comparisons across manufacturers, so authoritative cross-manufacturer excipient catalogues are scarce in the public domain ^{[6] [7] [8]}. The absence of broad comparative listings in these expert and regulatory documents does not contradict variability; it reflects differing documentary priorities — safety and residues over commercial formulation detail — and sometimes confidentiality around proprietary excipient blends ^{[6] [7]}. Where regulatory dossiers are public, they show product-specific excipients but do not create a consolidated marketwide inventory ^[1].

5. On undeclared ingredients: evidence points toward illicit or substandard supply chains, not standard manufacturing practice

The detection of undeclared active pharmaceutical ingredients and widespread noncompliance in seized or locally analyzed samples signals supply-chain integrity problems rather than routine manufacturer variation ^{[2] [3]}. Legitimate manufacturers disclose excipients in dossiers and follow pharmacopoeial standards, whereas falsified or substandard tablets commonly feature incorrect dosages, contamination, or undeclared substances. The South African and seizure studies both highlight public-health risks from these poor-quality products, suggesting that observed variability sometimes reflects illegal or negligent manufacturing rather than acceptable excipient diversity ^{[2] [3]}.

6. Putting the pieces together: a balanced conclusion for clinicians, regulators, and consumers

Taken together, the materials show that inactive ingredients do vary legitimately across ivermectin manufacturers, driven by formulation strategy and product optimization, and such variation can influence bioavailability and tablet behavior ^{[1] [5] [4]}. Concurrently, analytical studies demonstrate that market variability often includes dangerous deviations — undeclared actives and severe quality failures — primarily associated with falsified or substandard products rather than licensed manufacturers ^{[3] [2]}. Policymakers and clinicians should therefore differentiate between expected excipient diversity in authorized products and the red flags of illicit or poor-quality supplies.

7. What’s missing and where to look next for a definitive cross-manufacturer map

No single, recent consolidated dataset in these materials lists all excipients across global ivermectin manufacturers; the closest evidence comes from individual product dossiers and localized analytic studies ^{[1] [2]}. To create a definitive cross-manufacturer comparison, one would need systematic sampling of licensed products’ regulatory filings and independent laboratory analysis of market samples across regions; until such work is done, conclusions should rely on product dossiers for licensed formulations and on targeted market surveillance to detect substandard or falsified items ^{[1] [3]}.