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  • 2ml Injections with Diluent (Pack of 5) £122.50

This product is sourced in the United Kingdom and is intended for use in the United Kindgom only.

Zylexis is the first product in the UK which has been licensed as an immunmodulator for horses. Zylexis contains an inactivated virus which is unable to cause infection but acts as a super-antigen to boost the horse's immune system. It has been shown to reduce the effects of respiratory disease and improve performance.

Zylexis is provided in a pack of 5 injections (just 2mls each). It is advised to be used at times of stress or crowding. The recommended treatment course is one injection initially, another 2 days later and a final injection 1 week after that. Zylexis should be stored in the fridge and will be sent out in a cold pack.


Zylexis for Horses is presented as a lyophilisate and solvent for suspension for intramuscular injection.

Each 2 ml dose contains inactivated Parapoxvirus ovis, strain D1701 that generates a minimum of 460 IFN Units *.

*: interferon units as determined in an in vitro stimulation assay in cattle lymphocytes.


Zylexis for Horses acts by stimulation of non-specific immune mechanisms and is of potential clinical value in the reduction of clinical signs of equine respiratory disease associated with stress/crowding.

In a field study, reduction of clinical signs (defined as the first time-point at which significant differences were evident between groups) was shown on day 5 after administration of the full treatment schedule and lasted less than a week.

Dosage and administration

For horses from 10 months of age.

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 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-hour interval (day 0 and day 2) and the 3rd injection is administered on day 9.

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.

Advice on correct administration

Sterile needles and syringes should be used for administration.

Syringes and needles should not have been sterilised chemically or be above ambient temperature. Do not use chemicals to disinfect or sterilise skin.

Shake well before use.

Aseptic precautions should be observed.

Reconstituted vaccine should be used immediately.

Contra-indications, warnings, etc

In a study in which horses of 4-10 months of age were administered Zylexis for Horses according to the recommended dosage regime, no systemic or local reactions were observed.

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 to support the use of the authorised schedule in pregnant mares. One overdose (4 ml) was investigated in pregnant mares in the second half of pregnancy up to a few days before parturition.

No systemic or local reactions or negative effects were observed in these mares.

There is no information concerning safety in stallions.

No information is available on the safety and efficacy of this 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.

In an overdose (4 ml) safety study carried out in 1 day-old horses, no systemic or local reactions were observed.

Do not mix with any other veterinary medicinal product.

If you notice any serious effects or other effects not mentioned in this leaflet, please inform your veterinary surgeon.

All suspected adverse reactions and any suspected lack of efficacy should be reported to Pfizer Ltd technical helpline on 0845 300 8034.

Withdrawal period

Zero days.

Pharmaceutical precautions

Keep out of the reach and sight of children.

Store in a refrigerator (2°C – 8°C).

Protect from light.

Do not freeze.

Use immediately after reconstitution.

Do not use after the expiry date stated on the label.

For animal treatment only.


Any unused veterinary medicinal product or waste material should be disposed of in accordance with local requirements.

Legal category


Packaging Quantities

Boxes containing 5 glass vials of lyophilisate together with 5 glass vials of the solvent.

Further information

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.

This is a limited Marketing Authorisation. A full set of supporting efficacy data is not available for this product

Marketing authorisation number

Vm 00057/4421.

GTIN (Global Trade Item No)

5 x 2 ml:


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