Pain vs. Dysphoria

KREINby Stephanie Krein, DVM, DACVAA

One of the most frustrating clinical post-operative decisions to make can be differentiating between pain and dysphoria and deciding how to properly treat each of these. In human medicine the physician has the ability to ask the patient, “how are you feeling” or “what is your comfort level” and then to treat appropriately based on the answer. In veterinary medicine, our patients cannot talk or express to us what they are feeling, so they rely upon us to make the proper clinical decisions and implement the proper therapeutic technique. This article will attempt to differentiate between pain and dysphoria and briefly discuss the available treatment options for both.

Dysphoria is a profound state of unease or dissatisfaction accompanied by anxiety or agitation. Dysphoria can be very frustrating for the animal and the staff involved, and at times can be difficult to identify or treat. Clinical signs seen in a dysphoric animal include vocalization, panting, or struggling1. Dysphoria is commonly caused by the very treatment we are giving in attempts to remedy the pain an animal is experiencing. Opioids are commonly known to induce dysphoria in some animals and some species (cats more often than dogs). Opioid induced dysphoria is accompanied by an agitated animal that was recently treated for pain with opioids or an animal that does not respond to human contact1. Dysphoria caused by opioids can often be reversed with a low dose of a reversal drug such as butorphanol (a full mu antagonist and kappa agonist) or naloxone. An animal that is dysphoric from opioids should not be withheld pain medications and should be treated with a different class of analgesic or a different class of opioids. Often sedatives can be helpful in dysphoric animals. It is important though when sedating an animal to first ensure that their pain in being managed appropriately.

Sedatives used to treat dysphoria include acepromazine,  a phenothiazine, and dexmedetomidine, an alpha-2 agonist. These drugs both have different cardiovascular side effects and should be used carefully and in the correct patient. Acepromazine can be used in very small doses, such as 0.005-0.01 mg/kg IV, if given for sedation of a dysphoric patient post operatively. Acepromazine causes various effects including vasodilation and hypotension due to its antagonism of the alpha-1 receptors so should be used judiciously2. Acepromazine has no analgesic properties. Dexmedetomidine in very small doses, 0.5 mcg/kg (0.0005 mg/kg), can also be used to treat dysphoria in post-operative or hospitalized patients. Again, dexmedetomidine should be used only in the appropriate patients as it can cause initial vasoconstriction and bradycardia followed by hypotension3. A newer drug on the market used to treat anxious or dysphoric animals is Trazodone, a serotonin antagonist and reuptake inhibitor. Trazodone is an oral drug used at a dose of 3-10 mg/kg twice daily. The onset of Trazodone is relatively short, around 1-2 hours in most dogs. When starting Trazodone it is recommended to start low and increase the dose as you see the patient’s response. Trazodone should be used at low doses if giving other serotonin reuptake inhibitors such as Tramadol or drugs that affect serotonin levels such as acepromazine. Trazodone has been used with much success in dogs needing post op confinement at home4.

Pain is defined as “an unpleasant sensory or emotional experience associated with actual or potential tissue damage”5.  Pain is a complex multi-dimensional experience and a very individual experience. Pain can be chronic in nature (arthritic pain or neuropathic pain) or can be acute (post-operative/ post traumatic pain). The many different options for treating pain are beyond the scope of this article and other resources should be used for a thorough discussion. Although pain is unpleasant it is a necessary sensation in that it protects animals against potentially harmful stimuli. Pain receptors, also known as nociceptors, are the free endings of sensory neurons. The pain pathway starts at these nociceptors, extends up the sensory nerve fibers into the spinal cord where signals are modulated and sent up to the brain. The brain then perceives these signals and also sends signals back down to the spinal cord where again signals are modulated. The different drugs used to treat pain all act on different parts of the pain pathway and several of the drug classes act on multiple parts of the pathway. The fact that the drugs act on different parts of the pain pathway illustrates the importance of using multi-modal analgesia.

Different types of pain exist (inflammatory, neuropathic, post-surgical, chronic pain) requiring different classes of drugs to be used as treatment. The different types of drugs used to treat pain include opioids, NSAIDs, local anesthetics, alpha-2 agonists, drugs that affect serotonin or norepinephrine, NMDA antagonists, and gabapentin. Other modalities besides pharmacologic therapy can also be effective in treating different types of pain such as acupuncture, laser treatment, myofascial trigger point therapy, and rehab/physical therapy. It is important to treat the patient as an individual and adjust the dosages and classes of drugs used according to how that specific patient responds. Not all patients will respond the same way to the same treatment. It is also important to know the drug’s side effects prior to using it and to educate the clients on what to look for at home and what sort of monitoring will be needed with each medication.

pain-vs-dysphoria-photoRecognizing the difference between pain and dysphoria can be difficult, but is possible. Treating each patient as an individual and recognizing responses to therapy play an important role. The clinical signs of pain in cats and dogs can be difficult to recognize and sometimes to distinguish from dysphoria or anxiety. Clinical signs of pain in dogs include panting, crying, increased aggression, decreased appetite, decreased activity, withdrawal from owner, and agitation. Clinical signs of pain in cats vary widely from patient to patient and range from vocalization, tachypnea, agitation, and hyperthermia to withdrawal from owner and normal environment, hiding, lack of grooming, anorexia, and inactivity.  Remember cats are not small dogs and will react differently to various medications and to pain. When evaluating a patient, start from afar and then approach to palpate around the area of concern. Use the procedure type, the patient’s pain level and temperament, and the environmental setting to choose a treatment plan. Lastly, do not forget to use a multimodal approach as all pain and dysphoria are not equal and should not be treated as such.

For more information, please contact Angell’s Anesthesia Services at 617-541-5048 (


  1. Becker WM, Mama KR, Egger EL, et al. “Prevalence of Dysphoria after fentanyl in Dogs Undergoing Stifle surgery”. Veterinary Surgery. (2013) 42; 3, pp. 302-307.
  2. Lemke KA. “Anticholinergics and Sedatives” in Lumb & Jones’ Veterinary Anesthesia and Analgesia, 4th ed. Edited by Tranquilli WJ, Thurmon JC, Grimm KA. 2007, pp. 208-209.
  3. Lemke KA “Anticholinergics and Sedatives” in Lumb & Jones’ Veterinary Anesthesia and Analgesia, 4th ed. Edited by Tranquilli WJ, Thurmon JC, Grimm KA. 2007, pp. 210-225.
  4. Gruen ME, Simon CR, Sherman BL, et al. “Use of trazodone to facilitate postsurgical confinement in dogs”. JAVMA. 2014; 245, 3. Pp. 296-301.
  5. Lamont LA. “Multimodal Pain Management in Veterinary Medicine: The physiologic Basis of Pharmacologic Therapies”. Veterinary Clinics of North America-Small Animal Practice. 2008; (38)6,1173-1186.
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