Welfare fears at plans to restrict drug used for chronic pain

Vets fear proposals to restrict a key treatment used for chronic pain in dogs and cats to humans only could hit animal welfare.

While myriad licensed vet analgesic medications are available and prescribed, human antiviral amantadine is also used by vets because no licensed product is available for the treatment of central sensitization – a key feature of chronic pain in dogs and cats.

But amantadine, an M2 ion channel inhibitor used to treat human influenza, is included on a list of critical human medicines the European Medicines Agency (EMA) wants reserved solely for human use, to help protect against future resistance issues.

Although the proposals would not apply to the UK, anaesthesia and analgesia specialists fear UK regulators may take the same step – or market forces could mean it is much more difficult to source here.

Consultation

The European Commission opened a consultation on the full list last month, and vets worldwide have already raised concerns about potential restriction of amantadine.

RCVS and European specialist Matt Gurney, co-founder of the Zero Pain Philosophy website, has submitted a response in his role as president of the European College of Veterinary Anesthesia and Analgesia (ECVAA).

He cited “concern of a developing welfare issue should amantadine be restricted for human use”, and that it acts at the N-methyl-aspartate (NDMA) receptor to reduce central sensitization and reduce hyperalgesia associated with pain.

Study

A 2008 study by Lascelles et al is referenced, which concluded: “In dogs with osteoarthritic pain refractory to an NSAID, physical activity is improved by the addition of amantadine.”

The ECVAA’s consultation response concluded: “As European specialists in pain management, we urge you to reconsider this decision on the basis of the suffering that can be prevented through the use of amantadine.”

‘Second-line addition’

Speaking separately to Vet TimesDr Gurney said: “Amantadine has become a well-accepted second-line addition in our multimodal therapy for arthritis.

“Amantadine is a really useful tool; we’ve come a long way to understand that it is a good option. Yes, it is not a licensed option and there is only so much information we have, but this is where we are when we need to go beyond our licensed options in chronic pain.

“If amantadine was to go off the market completely, there is another NMDA antagonist called memantine, which we have used anecdotally, but we do not have any scientific studies or any evidence in dogs that it is actually an effective analgesic.

‘Welfare concern’

“There is a welfare concern there. I’m sure there are other options that we need to look at, but there might just be that gap while we take time to assess those other options. When I say gap, we are probably talking at least a year to get a study going, or maybe to look at alternative options. ”

Mr Gurney said amantadine use varied in EU countries, and was not available in some, including Denmark, but it was widely used elsewhere and in the UK.

He added: “This is an EU proposal; whether we’re protected from that in the UK, I do not know, but I guess there is still a risk that a regulatory body would take a view of: ‘Well, they’ve done this in Europe, so we will follow suit ‘.

“Or sometimes, manufacturers will make a decision: ‘Okay, [there’s] this decision in Europe, so we are going to apply it to the UK market as well ‘. ”

Submission

Ian Ramsey, a European Board of Veterinary Specialization-recognized renowned internal medicine specialist, has submitted to the consultation.

In his submission on the European Commission website, he supports restrictions on antimicrobials, but said amantadine’s inclusion on the list would “cause specific difficulties should it be removed from veterinary use” and its removal “is not scientifically justified”.

‘Important component’

The BSAVA is also concerned by the planned restriction of amantadine.

Sheldon Middleton, BSAVA president, said: “Amantadine is an important off-license component of multimodal analgesia in cats and dogs.

“The BSAVA is aware of the current European consultation about potentially restricting the use of this drug to humans only. Given the potential negative consequences for animal welfare of this restriction, the BSAVA supports the view that the drug should not be prevented from being used in cats and dogs. ”

UK review

The VMD confirmed EU laws on veterinary medicinal products were not retained when the UK left the bloc, but a review of this country regulations is imminent. On current amantadine usage by UK vets, a spokesperson said: “There is currently no UK-authorized veterinary medicinal product containing amantadine.

“A human medicine may be used under the cascade, but, as amantadine does not have a maximum residue limit, this active substance cannot be used in food-producing animal species.

“The VMD is currently in the process of reviewing the Veterinary Medicines Regulations 2013 and plans to publicly consult on proposed changes during 2022.”

Draft regulations

The EMA said that after the consultation on restricting antimicrobials closed, the European Commission was expected to finalize draft regulations soon. A spokesperson added: ”During the discussion [on antimicrobials] it was considered that alternatives to amantadine for the treatment of severe pain could include gabapentin or pregabalin, although some animals would not respond to these treatments.

“It was noted that amantadine is highly important for the treatment of influenza in humans and that there is a pathway for the transmission of resistance from animals to humans, hence the need to restrict use in animals.”

The full draft regulation is available at bit.ly/3PfOsXi

Reference

Lascelles BD et al (2008). Amantadine in a multimodal analgesic regimen for alleviation of refractory osteoarthritis pain in dogs, J Vet Intern Med 22(1): 53-59.

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