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Opioid use in Veterinary Patients: The Good, The Bad, and The Ugly

Written by Jennifer M. Rouse, DVM CCRP CVSMT Jan 5 • 3 minute read

Opioid use is a common topic in the news these days and the abuse epidemic has taken its toll in human medicine. These drugs are used and sometimes misused in veterinary medicine, too. When used appropriately, they can be a relatively safe and effective means to treat acute pain and aid in sedative and anesthetic protocols in animals. When used inappropriately, they can at best be ineffective in the treatment of chronic pain. At worst, they can cause serious or life threatening side effects, can increase pain long term, and can serve as a reservoir for human abuse. Today's blog takes a brief look at both why and why not to use opioids in our companion animals.  

What Are Opioids? 
Opioids are powerful prescription drugs that are designed to relieve pain. They work by binding to opioid receptors in the brain, which results in reduced perception of pain. They can be extremely effective at relieving moderate to severe pain, but also have potentially serious side effects if not used properly. When used in conjunction with other medications, some opioids sedative effects are part of a combination to induce sedation, or begin the anesthetic process for certain procedures. 

The Good: Opioids for Acute Pain! 
It's surgery day and your dog is going in for their spay or neuter. They are otherwise pain-free prior to the procedure, and despite undergoing a major procedure, we want to keep them as pain-free as possible. Additionally, we want to give them medications to help calm them so that we can prep them for other anesthetic drugs and surgery. That is were opioids come in! Given in hospital as an injection in combination with other medications, we can pre-emptively block pain signals and recognition of any signals that may make it through to the brain. Prevention of pain using a multimodal approach is always a better plan then treating it once it is perceived. For those patients that come in with acute pain (think trauma - hit by car, bone fracture, other wounds) it is also a reasonable medication to start with to initially block the pain pathways and assess whether additional medications or treatments are reasonble to administer. 

The Bad: Opioids for Chronic Pain- Administration and Efficacy 
When it comes to long-term opioid use for chronic pain there are several factors that make their use difficult. The first factor is how to adminster the medication. Opioids are generally in the form of injectable, oral, or in some cases transdermal preparations. Injectable forms are not sent home for routine owner administration for reasons ranging from the need for technical ability to adminster the medication properly and the high potential for misuse and abuse. Transdermal forms carry the potential for accidental human exposure which can be life threatening to those exposed. Oral forms can also be abused by humans but the additional concern in dogs is that oral administration has reduced efficacy due to the fact that dogs often do not achieve effective blood levels due to something called the "first pass effect." Drugs like tramadol are additionally problematic in that dogs do not metabolize the drug into active pain blocking components unlike humans and cats, so this drug often causes sedation but is ineffective in canine pain management. 

The Ugly: Risks of Long-Term Opioid Use in Dogs 
When it comes to long-term opioid use for chronic pain in dogs, there are several potential risks to consider. For one thing, opioids can be addictive and cause physical dependence even in animals. This means that if your pet has become dependent on opioid use, they may suffer withdrawal symptoms when they stop taking them. In addition, prolonged use of opioids can cause gastrointestinal issues such as vomiting or diarrhea, and can lead to liver or kidney damage over time. Furthermore, long-term opioid use can interfere with other medications that your dog is taking, resulting in serious side effects. The other newer concern is that opioids when used long term can cause increased pain through the nervous systems down regulation the mu receptor and can actually trigger increased pain sensitivity through interactions with NDMA receptors in the spinal cord. 

The Good News: Alternatives to Opioid Use for Chronic Pain Patients
Fortunately, there are alternatives to using opioids for chronic pain management in our companion animals. Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for this purpose and provide a much safer option than opioids do. Other treatments that can provide a multi-modal approach include physical therapy, chiropractic care,  and acupuncture treatments as well as supplements like CBD oil or glucosamine/chondroitin supplements to support joint health. Finally, massage therapy may help relieve muscle tension and improve circulation which can help reduce inflammation and improve mobility in pets with chronic pain conditions.

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