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POM-V Prescription Required Companion Animal

Insistor 10 mg/ml Solution for Injection for Dogs and Cats

Active ingredient: Methadone Hydrochloride

Form

Injection

Species

Cats Dogs

Manufacturer

VetViva Richter GmbH

VMD MA No.

57446/4011

What it's used for

Analgesia in dogs and cats. Premedication for general anaesthesia or neuroleptanalgesia in dogs and cats in combination with a neuroleptic drug.

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 Methadone Hydrochloride

  1. 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. 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.

Prescription required

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

Clinical information

Insistor 10 mg/ml Solution for Injection for Dogs and Cats — SPC Details

Source: VMD Summary of Product Characteristics (SPC). Last updated 27 Mar 2026.

Analgesia in dogs and cats.
Premedication for general anaesthesia or neuroleptanalgesia in dogs and cats in
combination with a neuroleptic drug.
Cats: Intramuscular use.
To ensure a correct dosage, body weight should be determined as accurately as
possible.
Analgesia
Dogs: 0.5 to 1 mg Methadone HCl per kg bodyweight, s.c., i.m. or i.v. (corresponding to
0.05 to 0.1 ml/kg)
Cats: 0.3 to 0.6 mg Methadone HCl per kg bodyweight, i.m. (corresponding to 0.03 to
0.06 ml/kg)
To ensure accuracy of dosing in cats, an appropriately calibrated syringe should be
used to administer the veterinary medicinal product.
As the individual response to methadone is variable, and depends partly on the dosage,
the age of the patient, individual differences in pain sensitivity and general condition the
optimal dosing regimen should be individually based.
In dogs, onset of action is 1 hour following subcutaneous administration, approximately
15 minutes following intramuscular injection and within 10 minutes following intravenous
injection. Duration of effect is approximately 4 hours following intramuscular or
intravenous administration.
In cats, following intramuscular administration, onset of action is 15 minutes and the
duration of effect is 4 hours on average.
The animal should be examined regularly to assess if additional analgesia is
subsequently required.
Premedication and/or neuroleptanalgesia
Dogs:
Methadone HCl 0.5-1 mg/kg bodyweight, i.v., s.c. or i.m. (corresponding to 0.05 to 0.1
ml/kg)
AN: 01748/2024 and 01749/2024Page 5 of 8
Combinations e.g.:
•
midazolam or diazepam.
Induction with propofol, maintenance with isoflurane in oxygen.
•
acepromazine
Induction with thiopentone or propofol to effect, maintenance with isoflurane in
oxygen or induction with diazepam and ketamine.
•
0.1 ml/kg), + α 2-agonist (e.g. xylazine or medetomidine).
Induction with propofol, maintenance with isoflurane in oxygen in combination with
fentanyl or total intravenous anaesthesia (TIVA) protocol: maintenance with
propofol in combination with fentanyl.
TIVA protocol: induction propofol, to effect. Maintenance with propofol and remifentanil.
Chemical-physical compatibility has only been demonstrated for dilutions 1:5 with the
following solutions for infusion: sodium chloride 0.9 %, Ringer’s solution, Ringer’s
lactate solution and glucose 5 %.
Cats:
•
ml/kg)
- Induction with benzodiazepine (e.g. midazolam) and dissociative (e.g. ketamine).
- With a tranquiliser (e.g. acepromazine) and NSAID (meloxicam) or sedative (e.g.
α2-agonist).
- Induction with propofol, maintenance with isoflurane in oxygen.
Doses are dependent on the desired degree of analgesia and sedation, desired duration
of effect and the concurrent use of other analgesics and anaesthetics.
When used in combination with other veterinary medicinal products, lower dosages can
be used.
For safe use with other veterinary medicinal products, reference must be made to the
relevant product literature.
The stopper should not be punctured more than 20 times.
Do not use in cases of hypersensitivity to the active substance or to any of the
excipients.
AN: 01748/2024 and 01749/2024Page 2 of 8
Do not use in animals with advanced respiratory failure.
Do not use in animals with severe liver and renal dysfunction.
Cats:
Very common
(>1 animal / 10 animals treated):
Respiratory depression
Lip licking
, Involuntary defecation
, Diarrhoea
Excitation
, Vocalisation
Urination
Mydriasis
, Hypersensitivity to pain
Hyperthermia
All reactions were transient.
Mild
Dogs:
Very common
(>1 animal / 10 animals treated):
Respiratory depression, Panting, Irregular breathing;
Bradycardia;
Lip licking, Hypersalivation;
Vocalisation;
Hypothermia;
Urination;
Involuntary defecation;
,2
Tremor, Staring.
All reactions were transient.
Mild
Occasional within the first hour post dose.
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. See the package leaflet for
respective contact details.
AN: 01748/2024 and 01749/2024Page 4 of 8
Due to the variable individual response to methadone, animals should be monitored
regularly to ensure sufficient efficacy for the desired duration of effect.
Use of the veterinary medicinal product must be preceded by a thorough clinical
examination.
In cats, pupil dilation is seen long after the analgesic effect has disappeared. It is
therefore not an adequate parameter to assess clinical efficacy of the administered
dose.
Greyhounds may require higher doses than other breeds to achieve efficacious plasma
levels.

Special precautions for safe use in the target species:
Methadone may occasionally cause respiratory depression and, as with other opioid
drugs, care should be taken when treating animals with impaired respiratory function, or
animals that are receiving drugs that can cause respiratory depression. To ensure safe
use of the veterinary medicinal product, treated animals should be monitored regularly,
including examination of heart rate and respiratory rate.
As methadone is metabolised by the liver, its intensity and duration of action may be
affected in animals with impaired liver function.
In case of renal, cardiac or hepatic dysfunction, or shock, there may be greater risk
associated with the use of the veterinary medicinal product.
The safety of methadone has not been demonstrated in dogs less than 8 weeks and
cats less than 5 months of age.
The effect of an opioid on head injury is dependent on the type and severity of the injury
and the respiratory support supplied.
Safety has not been fully evaluated in clinically compromised cats. Due to the risk of
excitation, repeated administration in cats should be used with care.
The benefit/risk ratio for using the veterinary medicinal product should be made by the
attending veterinarian.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals:
Methadone can cause respiratory depression following spillage on the skin or accidental
self-injection. Avoid skin, eyes and mouth contact, and wear impermeable gloves when
handling the veterinary medicinal product. In cases of spillage onto the skin, or
splashing into the eyes, wash immediately with large amounts of water. Remove
contaminated clothes.
People with known hypersensitivity to methadone should avoid contact with the
veterinary medicinal product. Methadone has the potential to cause stillbirths. Pregnant
women are advised not to handle the veterinary medicinal product.
AN: 01748/2024 and 01749/2024Page 3 of 8
In the case of accidental self-injection, seek medical advice immediately and show the
package leaflet or the label to the physician but DO NOT DRIVE as sedation may occur.
To the physician: Methadone is an opioid whose toxicity may cause clinical effects
including respiratory depression or apnoea, sedation, hypotension and coma. When
respiratory depression occurs controlled ventilation should be initiated. Administration of
the opioid antagonist naloxone to reverse the symptoms is recommended.
Special precautions for the protection of the environment:
Not applicable.
For concurrent use with neuroleptics refer to section
This veterinary medicinal product does not require any special temperature storage
conditions.
Keep the vial in the outer carton in order to protect from light.
Not applicable.
4.

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.

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