Intrathecal morphine overdose in a dog

Abstract

Although intrathecal administration of an overdose of morphine can be associated with major and potentially fatal complications, it is possible that affected dogs can completely recover with immediate treatment and extensive supportive care.

Myoclonus and hyperalgesia following intended epidural morphine administration in a dog

“…It is more commonly seen following chronic exposure, but has been reported in humans and animals following single high doses (Angst and Clark 2006). Myoclonus, brief, shock-like contractions of a muscle or group of muscles, is less common but has been reported following intrathecal administration of preservative-free morphine in dogs at normal doses (Kona-Boun and others 2003, Iff and others 2012) and following inadvertent overdose (Da Cunha and others 2007). Myoclonus with hyperalgesia has been reported in humans receiving chronic pain management with repeated large doses of intrathecal morphine (Krames and others 1985, De Conno and others 1991).…”

“…When used in a case of intrathecal morphine overdose in a dog (Da Cuhna and others 2007), effects quickly diminished with repeated doses until no effect was seen. Ketamine, an NMDA receptor antagonist, has also been reported to resolve hyperalgesia and myoclonus following chronic intrathecal opioid administration in a person when given as a low dose infusion (Forero and others 2011).…”

“…Both of these could have been used as additional medication in this patient if clinical signs persisted. Naloxone has been shown to be ineffective in a number of cases (Werz and MacDonald 1982, Da Cuhna and others 2007), which is possibly because the neuroexcitatory effects of morphine are not opioid receptor medicated (Werz and MacDonald 1982). A number of other medications have been used in existing case reports involving dogs and include intravenous phenobarbitone, pentobarbitone, atracurium, acepromazine and butorphanol with varying degrees of success (Kona-Boun and others 2003, Da Cuhna and others 2007, Iff and others 2012).…”

An Update on Drugs Used for Lumbosacral Epidural Anesthesia and Analgesia in Dogs

“…The use of a 5-hydroxytryptamine antagonists (e.g., ondansetron) has been described as treatment for neuraxial opioid-induced pruritus (102). Myoclonic activity upon recovery from anesthesia was also reported following intrathecal administration of morphine in dogs (15, 100) but this is not a clinical issue with epidural injections, providing that the maximum dose of 0.1 mg kg −1 is respected and accidental puncture of the subarachnoid space does not take place during needle insertion (103). Studies showed that approximately 3% of dogs receiving epidural morphine showed urinary retention postoperatively (6, 104).…”

Reversible Paralysis and Loss of Deep Pain Sensation After Topical Intrathecal Morphine Administration Following Durotomy

“…In our report, both dogs were treated with 0.5 mg/kg topical morphine for postoperative analgesia. This dosage exceeds previously reported dosages for epidural and intrathecal administration in dogs (0.05–0.2 mg/kg). When morphine is applied directly to the epidural space during surgery, a considerable amount of the drug is either absorbed systemically through the venous network of the surrounding soft tissue and spinal canal or is externally eliminated by irrigation and suction.…”