Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed
This FDA product-safety summary reviewed arsenic-based animal drugs and poultry with a specific focus on how an arsenical feed drug (3-Nitro®/roxarsone) used in poultry production might contribute to inorganic arsenic in edible tissues. The page explains the underlying toxicological concern that organic arsenic (generally less toxic) can convert to inorganic arsenic (more toxic) and describes how FDA scientists responded by developing an analytical method sensitive enough to detect very low inorganic arsenic levels in edible tissues. For the Heavy Metal Tested and Certified (HMTC) context, the key regulatory idea is that a product can be “approved” yet still create heavy-metal risk pathways once real-world biotransformation and tissue distribution are measured with sufficiently sensitive methods, shifting risk management from assumptions about chemical form to verified speciation in target tissues.
Who was reviewed
The FDA summary centers on food-producing poultry, particularly broiler chickens evaluated under conditions that included treatment with 3-Nitro® and comparison to untreated controls. It also addresses turkeys and chickens through discussion of Histostat (nitarsone), an arsenic-based drug approved for preventing histomoniasis (blackhead disease). Although the page does not present full experimental protocols, it clearly identifies the relevant populations for HMTC-style certification decisions: commercially relevant poultry species and edible tissues (with particular emphasis on liver findings). In practical terms, the “who” is the set of animals whose tissues enter the human food supply and therefore define downstream dietary exposure, making arsenic-based animal drugs and poultry a supply-chain issue rather than a narrow veterinary pharmacology topic.
Most important findings
For arsenic-based animal drugs and poultry, the FDA summary highlights that improved analytical sensitivity changed what regulators could reliably detect and therefore what they could credibly regulate. The most certification-relevant takeaway is that inorganic arsenic increased in the livers of treated chickens versus untreated controls, triggering market and regulatory actions that progressively removed arsenical drugs from U.S. animal feed use.
| Critical point | Details |
|---|---|
| Organic-to-inorganic conversion risk | Published scientific reports indicated that organic arsenic (the form in roxarsone/3-Nitro®) could transform into inorganic arsenic, reframing risk around speciation rather than total arsenic. |
| Methodological pivot enabled enforcement-grade detection | FDA scientists (CVM and CFSAN) developed an analytical method capable of detecting very low inorganic arsenic levels in edible tissue, reducing uncertainty for compliance and certification thresholds. |
| Treated vs. control tissue difference | Using the new method, FDA scientists found inorganic arsenic levels in livers of chickens treated with 3-Nitro® were increased relative to untreated control chickens—directly relevant to edible offal risk management. |
| Voluntary suspension and withdrawals narrowed exposure pathways | Alpharma (Pfizer subsidiary) voluntarily suspended 3-Nitro® sales; later Zoetis continued the suspension and on Feb 27, 2014 withdrew the application; Zoetis and Huvepharma AD also voluntarily withdrew approvals for 3-Nitro®, arsanilic acid, and carbarsone for use in animal feed (including combinations). |
| “Last arsenical” phase-out created an implementation cliff | Zoetis announced April 1, 2015 it would discontinue marketing Histostat (nitarsone) by fall 2015 and seek withdrawal by end of 2015; FDA noted it would not be available for the 2016 growing season, creating a defined transition point for industry controls. |
| Disease-control tradeoff acknowledged | Histostat was described as the only approved animal drug for preventing histomoniasis (blackhead disease) in turkeys and chickens, underscoring that heavy-metal risk mitigation can collide with animal-health needs and requires alternatives planning. |
Key implications
For arsenic-based animal drugs and poultry, the primary regulatory impact is that arsenic speciation in edible tissues can justify removal of approvals and medicated-feed combinations when inorganic arsenic elevation is demonstrated. HMTC certification requirements should therefore include speciation-capable testing in relevant tissues or products, documentation that no arsenical feed drugs are used, and supplier attestations aligned to post-withdrawal market reality. Industry applications include updating medication protocols, strengthening residue monitoring, and validating alternative disease controls where arsenicals were “last-resort” tools. Research gaps include clearer dose–tissue relationships, tissue-to-product transfer under varied husbandry, and standardized sampling plans for certification audits. Practical recommendations are to test beyond muscle when warranted, set action triggers for inorganic arsenic, and harden traceability from feed to flock to finished lots.
Citation
U.S. Food and Drug Administration. Arsenic-based Animal Drugs and Poultry. FDA website. Content current as of April 29, 2022. Accessed January 19, 2026.
Arsenic is a naturally occurring metalloid that ranks first on the ATSDR toxic substances list. Inorganic arsenic contaminates water, rice and consumer products, and exposure is linked to cardiovascular disease, cognitive deficits, low birth weight and cancer. HMTC’s stringent certification applies ALARA principles to protect vulnerable populations.
