POM-V Prescription Required

Myorelax 100 mg/ml Solution for Infusion for Horses

Active ingredient: Guaifenesin

Form

Solution

Species

Horses

Manufacturer

Eurovet Animal Health B.V.

VMD MA No.

16849/5010

What it's used for

Induction of muscle relaxation and immobilisation, as an adjunct to balanced anaesthesia. Depending on the procedure, guaifenesin can be used in combinatio...

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 Guaifenesin

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.

Your prescription rights → VMD register of retailers →

Prescription required

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

Clinical information

Myorelax 100 mg/ml Solution for Infusion for Horses — SPC Details

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

Induction of muscle relaxation and immobilisation, as an adjunct to balanced
anaesthesia.
Depending on the procedure, guaifenesin can be used in combination with
different anaesthetics:
- in combination with a sedative, and local anaesthetics for short procedures
- in combination with appropriate general anaesthetics, for induction and/or
maintenance of muscle relaxation during anaesthesia.

None.

Revised June 2024
AN: 00468/2023

Horses:
Undetermined frequency (cannot be
estimated from the available data):
Hypotension, Thrombophlebitis
a
, Injection site
reaction
b
a
due to irritative properties. To reduce the incidence of thrombophlebitis, the
catheter can be flushed with heparinised saline.
b
extravascular reactions have been reported; the use of an intravenous catheter
and careful technique will help prevent such occurrences.

Revised June 2024
AN: 00468/2023
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian,
to either the marketing authorisation holder or its local representative or the
national competent authority via the national reporting system. Seethe package
leaflet for respective contact details.

Guaifenesin should not be used alone. Animals must be properly sedated before
immobilisation with the veterinary medicinal product. Adequate analgesia should
always be provided for surgical and/or painful procedures. Animals should undergo
a thorough pre-anaesthetic examination before administration of the product.
Except in the case of an acute emergency, feed should be withheld for 12 hours
prior to anaesthesia. Water should be freely available until a short time before
anaesthesia.

Special precautions for use in animals
Due to the irritative effects of the solution, it should be administered strictly
intravenously using a catheter. See also section 4.6.
Animals with anaemia, cardiac or respiratory problems or animals with other signs
of disease should be monitored extra carefully.
Special precautions to be taken by the person administering the veterinary
medicinal product to animals
People with known hypersensitivity to guaifenesin should avoid contact with the
veterinary medicinal product.
Take care to avoid skin or eye contact. In case of accidental skin contact wash
affected area thoroughly. If irritation occurs/persists, seek medical advice. In case
of accidental eye contact flush thoroughly with clean water and seek medical
advice immediately, showing the product label to the physician.
Special precautions for the protection of the environment
Not applicable.
Other precautions
Not applicable.

The action of anaesthetic agents is potentiated by guaifenesin.

This veterinary medicinal product does not require any special storage conditions.

For the full list of excipients, see section

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.