POM-V Prescription Required

Zylexis for Horses

Active ingredient: Orf virus

Form

Injection

Species

Horses

Manufacturer

Zoetis UK Limited

VMD MA No.

42058/5208

What it's used for

Zylexis for horses acts by stimulation of the non-specific immune mechanisms and is of potential clinical value in the reduction of clinical signs of stres...

Full indications, dosage and side effects ↓

View official SPC (PDF)

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Paying less for Orf virus

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

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Clinical information

Zylexis for Horses — SPC Details

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

Zylexis for horses acts by stimulation of the non-specific immune mechanisms and
is of potential clinical value in the reduction of clinical signs of stress/crowding
associated equine respiratory disease.
In a field study, reduction of clinical signs (defined as the first time-point at which
significant differences were evidenced between groups) was shown on day 5 after
administration of the full treatment schedule and lasted less than a week. This is a
Limited Marketing Authorisation. A full set of supporting efficacy data is not
available for this product.

Revised: May 2025
AN: 00173/2025

Aseptically reconstitute the lyophilisate with the solvent provided. Shake well
before use. The entire contents of the reconstituted vial should be administered
intramuscularly as a single dose, irrespective of the body weight of the animal.
Dosage regimen
Three injections of a single dose for each animal are recommended.
The first two injections are administered with a 48-hours interval (day 0 and day 2)
and the third injection should be administered on day 9.

None.

Hyperthermia associated with general malaise and musculoskeletal signs
(stiffness, abnormal posture, tense muscle) have been observed very rarely in
spontaneous reports.
Hypersensitivity reactions (i.e. circulatory shock, tachycardia, abdominal pain,
convulsion) may occur very rarely. Such reactions may evolve to a more severe
condition (anaphylaxis), which may be life-threatening.
The frequency of adverse reactions is defined using the following convention:
- very common (more than 1 in 10 animals treated displaying adverse reaction(s))
- common (more than 1 but less than 10 animals in 100 animals treated)
- uncommon (more than 1 but less than 10 animals in 1,000 animals treated)
- rare (more than 1 but less than 10 animals in 10,000 animals treated)
- very rare (less than 1 animal in 10,000 animals treated, including isolated
reports).

To ensure efficacy of the treatment, it is important that the first dose of the product
is administered shortly before or up to the day of crowding or exposure to other
stressful conditions. It is important that the complete treatment schedule of 3
doses is administered.

Special precautions for use in animals
The product should not be used for treatment of animals with chronic diseases
with unclear causality.
Special precautions to be taken by the person administering the veterinary
medicinal product to animals
In case of accidental self-injection, seek medical advice immediately and show the
package leaflet or the label to the physician.

No information is available on the safety and efficacy of this immunological
veterinary medicinal product when used with any other veterinary medicinal
product. A decision to use this product before or after any other veterinary
medicinal product therefore needs to be made on a case by case basis.

Revised: May 2025
AN: 00173/2025

Store in a refrigerator (2 °C – 8 °C). Protect from light. Do not freeze.

Zero days.
5. IMMUNOLOGICAL PROPERTIES
The exact mechanism of action of inactivated parapoxvirus ovis is not fully
understood but may involve the stimulation and increase of the non-specific
immune mechanisms.
In a mouse model, it has been demonstrated that parapoxvirus ovis induces an
autoregulatory cytokine response that involves the up regulation of T helper (Th)
1 type cytokines (IL-12, IL-18, IFNγ) and their subsequent down regulation which
is accompanied by induction of IL-4. Furthermore, parapoxvirus ovis induces
phagocytic activity and oxidative burst in various animal species including horses
as demonstrated by ex vivo experiments.
In horses, it has been shown that administration of the product stimulates the
proliferation of lymphocytes and increases the production of IFNγ in vivo.
It was also shown that administration of the product to horses increases the
production of other cytokines such as TNFα, IFN β, IL15 and IL18 in vivo.
ATCvet code: QL03AX.

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.