POM-V Prescription Required

Trimediazine Plain Oral Powder

Active ingredients: Sulfadiazine, Trimethoprim

Form

Powder

Species

Horses

Manufacturer

Vetoquinol SA

VMD MA No.

06462/3012

What it's used for

Trimediazine Plain is indicated for use in the treatment of bacterial diseases in horses, including upper and lower respiratory tract infections, alimentar...

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 Sulfadiazine + Trimethoprim

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

Trimediazine Plain Oral Powder — SPC Details

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

Trimediazine Plain is indicated for use in the treatment of bacterial diseases in
horses, including upper and lower respiratory tract infections, alimentary tract
infections and infected wounds.

For oral administration in the feed.
To be given at a rate of 30 mg combined active ingredients per kg bodyweight.
Mix with a small quantity of feed. Each 50 g sachet provides a daily dose for a
500 kg horse and may be administered daily or divided and administered at 12
hourly intervals, for 5 days.
It is recommended that other feed be withdrawn until medicated feed has been
consumed.

Do not use in horses with severe liver parenchymal damage or kidney damage
or known sulphonamide sensitivity, or horses with blood dyscrasias or cardiac
arrhythmias.
Do not exceed 7 days continuous treatment.
Do not use in known cases of resistance to trimethoprim and sulphonamides.

None known

The use of Trimediazine Plain in horses under 1 year old should be avoided.

(i) Special precautions for use in animals
To avoid possible crystalluria, adequate water intake is essential.

Revised: November 2025
AN: 02390/2025
Use of the product should be based on identification and susceptibility
testing of the target pathogen(s). If this is not possible, therapy should be
based on epidemiological information and knowledge of susceptibility of
the target bacteria at farm level, or at local/regional level. Use of the
product should be in accordance with official, national and regional
antimicrobial policies. Use of the product deviating from the instructions
given in the SPC may increase the prevalence of bacteria resistant to the
product and may decrease the effectiveness of treatment with other
antimicrobials or classes of antimicrobials due to the potential for cross-
resistance.
(ii) Special precautions to be taken by the person administering the
veterinary medicinal product to animals
Persons handling this product should avoid inhalation of any dust and
contact with skin. Wear either a disposable half-mask respirator
conforming to European Standard to EN149 or a non-disposable
respirator to European Standard to EN140 with filter EN143 when
mixing or handling this product. Rubber gloves should be worn when
mixing or handling this product. Hands should be washed thoroughly
after use. Sulphonamides may cause hypersensitivity (allergy)
following injection, inhalation, ingestion or skin contact.
Hypersensitivity to sulphonamides may lead to cross reactions with
other antibiotics. Allergic reactions to these substances may
occasionally be serious.
1. Do not handle this product if you know you are sensitive to
sulphonamides.
2. If you develop symptoms following exposure such as a skin
rash, you should seek medical advice and show the doctor this
warning.

None known.

For a 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.