POM-VPS Prescription Required

Nytox 1000 mg/g Powder for Solution for Fish Treatment

Active ingredient: Tricaine methanesulfonate

Form

Powder

Species

Fish Ornamental Fish

Manufacturer

VIRBAC

VMD MA No.

05653/4229

What it's used for

For use in an immersion bath for sedation, immobilisation and anaesthesia of fish for: vaccination, transportation, weighing, tagging, clipping, stripping...

Full indications, dosage and side effects ↓

View official SPC (PDF)

The prescription itself has a price. See what practices near you charge for a consultation and the written prescription fee.

Paying less for Tricaine methanesulfonate

1

Ask your vet for a written prescription

They must provide one on request. Under the CMA Order the fee is capped at £21 from 2027.
2

Fill it at a registered online retailer

The CMA found online pharmacies 50–60% cheaper than practice dispensing on common medicines — typically £200–£300 a year.

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Prescription required

Your vet must provide a written prescription on request. You can then purchase from any licensed online retailer.

Clinical information

Nytox 1000 mg/g Powder for Solution for Fish Treatment — SPC Details

Source: VMD Summary of Product Characteristics (SPC). Last updated 26 Mar 2026.

For use in an immersion bath for sedation, immobilisation and anaesthesia of fish for:
vaccination, transportation, weighing, tagging, clipping, stripping of breed stock,
blood-sampling and surgical procedures.

An aqueous solution of the product is used in an immersion bath for sedation,
immobilisation and anaesthesia of fish, both ornamental and those intended for
human consumption.
A number of factors influence the efficacy and safety of the product, including
concentration of the drug in water, duration of exposure, temperature, oxygen and
density of biomass. Because of these variable factors it is strongly recommended
that a test of the selected drug concentration and exposure time is conducted with a
small group of representative fish before large numbers are medicated, particularly
when water temperature is at the upper or lower ends of the normal temperature
ranges for the species being treated. The product should be dissolved in water of the
same composition and characteristics as that to which the fish are accustomed. As
the product has good aqueous solubility, it may be added directly to the container.
Effects on the fish should be monitored as the product is gradually introduced.
Before anaesthesia, or prolonged sedation, fish should be fasted for 12 to 24 hours.
During treatment they should be stocked at a density not exceeding 80g/litre. To
minimise damage and loss when medicated for long periods for transport etc. the
level of sedation should allow fish to maintain their equilibrium and swimming
position. Aeration should be provided unless sedation, or anaesthesia, is of short
duration. In anaesthesia loss of reflexes takes place in one to fifteen minutes after
immersion depending upon concentration employed. Narcotised fish should be
removed from medicated water and returned to their normal environment as soon as
possible, when recovery will take between one and thirty minutes.
The following examples of dose rates and exposure times are based on laboratory
and field experience:-
Concentration
Mg/litre of
water
Immersion
time (mins)
Trout species (7-
17ºC)
Sedation10-30Up to 480AnaesthesiaLight
Deeper
30-80
80-180
Up to 30
Up to 10
Salmon speciesSedation7-30Up to 240AnaesthesiaLight
Deeper
30-80
80-100
Up to 10
Up to 5
Bass speciesSedation8-30Up to 480AnaesthesiaLight
Deeper
30-70
70-100
Up to 20
Up to 4
Carp speciesSedation20-30Up to 1440Anaesthesia30-200Up to 8Fresh water tropical fishSedation30-50Up to 1440

Amended pages: June 2023
AN: 03987/2022Page 4 of 6

Do not use with the following tropical fish species:
Apistogramma (Mikrogeophagus) ramirez, Balantiocheilos melanopterus, Etroplus
suratensis, Melanotaenia maccullochi, Monodactylus argenteus, Phenacogrammus
interruptus and Scatophagus argus.

None known.

None.

Special precautions for use in animals
Do not exceed the dose recommended for each category of fish.
Brood stock anaesthetised for stripping should be immersed in unmedicated water
immediately before collection of eggs or milt to avoid significant direct contact of
either with the product.

Amended pages: June 2023
AN: 03987/2022Page 2 of 6
As solutions of the veterinary medicinal product are slightly acidic, the use of
phosphate or imidazole buffer has been proposed to reduce stress.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals
People with known hypersensitivity to tricaine methanesulfonate should avoid contact
with the veterinary medicinal product.
Impermeable rubber gloves should be worn when handling the veterinary medicinal
product.
Avoid contact with skin and eyes. In case of accidental contact, immediately wash
the affected area with plenty of clean running water. If irritation persists, seek medical
advice.
Do not create dust when handling the powder or preparing the anaesthetic solution.
In case of accidental inhalation of dust, move to fresh air and if breathing is affected,
seek medical advice immediately and show the package leaflet or the label to the
physician.
In situations where dust is created when handling the product, wear a disposable half
mask respirator conforming to European Standard EN 149 or a non-disposable
respirator to European Standard EN 140 with a filter to EN 143.
Do not eat, drink or smoke whilst handling this product.
Wash hands after use
In case of accidental ingestion, seek medical advice immediately and show the
package leaflet or the label to the physician.
Other Precautions
In order to protect the environment, used solution must either be filtered using
activated charcoal filters prior to dilution in the effluent to be discharged from the farm
or it must be transferred to a holding tank filled with water with subsequent controlled
release for dilution in the effluent to be discharged from the farm. See section 6.6.
.

None known.

Amended pages: June 2023
AN: 03987/2022Page 3 of 6

Withdrawal period: 70 degree days after the end of treatment
Fish must not be slaughtered for human consumption during treatment.
Do not use during stripping of fish eggs intended for human consumption.
5.

This information is sourced from the official Summary of Product Characteristics (SPC) published by the Veterinary Medicines Directorate (VMD). It is provided for informational purposes only and does not replace professional veterinary advice. Always consult your vet before administering any medication.