Naloxone

What are opioids and how do they work?

Opioids are substances that bind to opioid receptors and can therefore relieve pain, calm or euphorize. They are often used in veterinary medicine as painkillers or as a component of anesthetics. Opioids include natural substances such as morphine or codeine, which are extracted from the opium poppy, as well as synthetic or semi-synthetic substances such as fentanyl, buprenorphine or tramadol.

The effect of opioids depends on the dose, the potency, the form of administration and the individual response of the animal. In addition to the pain-relieving effect, opioids can also have other effects, such as

• Sedation
• euphoria
• nausea
• vomiting
• constipation
• itching
• Respiratory depression
• bradycardia
• hypotension
• miosis

What is an opioid overdose and how do you recognize it?

An opioid overdose can occur if a dog is given too much or too often of an opioid, or if it accidentally eats an opioid intended for humans. Overdose can also be caused by interactions with other medications or by an individual dog's hypersensitivity.

The symptoms of an opioid overdose are:

• Severe sedation or unconsciousness
• Very slow and shallow breathing
• Blue mucous membranes
• Very low blood pressure and pulse
• Very small pupils

An opioid overdose is a life-threatening emergency and must be treated immediately. If a dog shows signs of overdose, it should be taken to the vet as soon as possible.

How does naloxone work in opioid overdose?

Naloxone is a specific antagonist of opioids, which means that it binds to the same receptors as the opioids, but without triggering an effect. As a result, it displaces the opioids from the receptors and cancels or weakens their effect. Naloxone acts primarily at the μ-receptors, which are responsible for most opioid-induced effects.

Naloxone can be administered intravenously, intramuscularly or subcutaneously. The dosage depends on the amount and potency of the opioid and the condition of the dog. Naloxone takes effect very quickly, usually within minutes. However, the duration of action of naloxone is shorter than that of many opioids, so naloxone may need to be administered repeatedly or as an infusion until the opioid is completely eliminated from the body.

The administration of naloxone may have some side effects, such as:

• Agitation or aggression
• sensitivity to pain
• tachycardia
• hypertension
• Nausea or vomiting
• pulmonary edema

These side effects are mostly due to the sudden withdrawal of the opioid effect and can be avoided or alleviated by slow and careful dosing of naloxone.

What other uses does naloxone have in dogs?

In addition to treating opioid overdose, naloxone can also be used for other indications in dogs, such as

• False pregnancy: naloxone can reduce the symptoms of false pregnancy such as milk production, nesting or maternal behavior by inhibiting the effect of endogenous opioids on prolactin secretion.
• Behavioral abnormalities: Naloxone can help dogs suffering from stereotypies such as tail biting, acral lick dermatitis or self-mutilation by blocking the effect of endogenous opioids on the reward system in the brain.

However, the dosage and effectiveness of naloxone in these applications are not well researched and may vary depending on the dog.