AQUI-S® E10% (eugenol immersion solution) for freshwater finfish sedation receives FDA approval

September 10, 2026

Sedative solution for field use helps manage fish and support fish welfare during spawning, tagging, weighing and measuring activities

RAHWAY, N.J., Sept. 10, 2026 — Merck Animal Health, known as MSD Animal Health outside of the United States and Canada, a division of Merck & Co., Inc., Rahway, N.J., USA (NYSE: MRK), today announced that the U.S. Food and Drug Administration (FDA) has approved AQUI-S^® E10% (eugenol immersion solution) for sedation of freshwater finfish to a handleable condition in field-use settings. AQUI-S New Zealand Limited is the sponsor and manufacturer of AQUI-S E10%, which is marketed and distributed by Merck Animal Health in the U.S.

AQUI-S E10% is a stable sedative solution containing the active ingredient eugenol that can be used to sedate fish during field-based resource management activities, including spawning, tagging, weighing and measuring. After fully recovering from sedation, fish may be released immediately back into their natural water body. The FDA-approved indication does not permit the use of AQUI-S E10% in fish held in confined settings, such as hatcheries, ponds or aquariums.

“This approval provides field users of the product a practical, easy-to-use, rapid option for sedating small numbers of fish to a handleable condition and releasing them quickly back to the wild after full recovery in freshwater,” said Tim Kniffen, DVM, MS, technical services veterinarian, North America Aqua business unit, Merck Animal Health. “The ready-to-use liquid formulation of AQUI-S E10% has a demonstrated margin of safety for salmonids as well as nonsalmonids and produces a rapid effect and recovery with no withdrawal period and immediate release after full recovery.”

The approved dosage range is 25 to 40 mg/L of eugenol for salmonid fish species and 40 to 100 mg/L of eugenol for nonsalmonid fish species. After handling, sedated fish should be placed in clean, well-aerated freshwater until fully recovered before release.

AQUI-S E10% is available in 1-liter and 4-liter presentations. The product is formulated to be added directly to treatment tanks and disperses easily with mixing to create a uniform concentration of the active ingredient in the water. No withdrawal period is required when AQUI-S E10% is used according to label directions.

Current and prospective INAD investigators will continue to have access to AQUI-S 20E. INAD customers can continue to access AQUI-S 20E through established channels.

AQUI-S E10% will be commercially available in the fourth quarter of 2026. For more information about AQUI-S E10%, contact a Merck Animal Health sales or technical services representative or visit https://www.merck-animal-health-usa.com/producers/aquaculture/.

IMPORTANT SAFETY INFORMATION for AQUI-S^® E10% (eugenol immersion solution):
For field-use only in freshwater finfish. Do not leave fish unattended during treatment. No withdrawal period is required when used according to labeling. Not for use in humans. Keep out of reach of children. Harmful if swallowed. May cause skin and eye irritation and skin sensitization. For complete safety information, refer to the product label.

Product Label

The FDA granted approval of AQUI-S^® E10% (eugenol immersion solution) for sedating freshwater finfish to a handleable condition in field-use settings. AQUI-S E10% is a stable sedative solution containing the active ingredient eugenol that is used during field-based resource management activities, including spawning, tagging, weighing and measuring.

About Merck Animal Health

Merck Animal Health, a division of Merck & Co., Inc., Rahway, N.J., USA, is a global animal health business committed to The Science of Healthier Animals™. For more than 130 years, we have pioneered groundbreaking science. Today, we are driven by continuous innovation to develop breakthrough medicines, vaccines and technology. Rooted in direct experience on the farm and in the clinic, we work hand in hand with our customers every step of the way. Our singular focus is to empower those who care for animals, helping them manage their vital responsibility with confidence. Because when it comes to animal health, no one sees it like we do. For more information, visit www.merck-animal-health.com and connect with us on LinkedIn, Facebook, X (formerly Twitter) and Instagram.

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