Neurologic complications after melarsomine dihydrochloride treatment for Dirofilaria immitis in three dogs

Abstract

Melarsomine dihydrochloride is highly effective against both sexes of adult and L5 Dirofilaria immitis. Common adverse reactions include injection site irritation and reluctance to move. Neurologic complications associated with i.m. injection of melarsomine dihydrochloride for treatment of heartworm disease in 3 dogs are described. Different degrees of neurologic complications have been identified; the pathophysiologic features are unknown. It is speculated that the compound migrates out of the injection site via fascial planes and causes an ascending inflammation along nerve roots. The resulting extradural cord compression secondary to extensive inflammation and necrosis of epidural fat could induce a variety of neurologic deficits. Alternatively, inappropriate injection technique may result in direct contact of melarsomine with neural tissue. A heightened awareness of proper injection technique might prevent the development of most neurologic complications.

The animal trypanosomiases and their chemotherapy: a review

“…Side effects to the drug are usually mild (salivation, lacrimation, muscle tremors, increased gut motility and frequent urination), but a severe adverse reaction has also been documented (Berlin et al 2010). Reports of neurological sequelae in dogs (Hettlich et al 2003), albeit perhaps not analogous to the reactive encephalopathy associated with melarsoprol treatment of humans (Blum et al. 2001), are notable.…”

Extensive Epidural Steatitis and Epaxial Myositis Associated with Intramuscular Injection of Melarsomine Dihydrochloride in Two Dogs

“…Previous reports have documented focal epidural steatitis in proximity to the injection site, thought to be a result of drug extension along spinal nerves, direct injection into the vertebral canal or aberrant heartworm larval migration. [4][5][6] In contrast, the dogs herein had extensive epidural steatitis and a consequent compressive myelopathy. Transverse myelitis is a rarely reported complication described in people receiving intramuscular injections of steroids or antibiotic medications with aberrant injection into nerve roots.…”

“…Decompressive surgery has resulted in improved neurological function in dogs with neurological dysfunction secondary to melarsomine. 4,5 Although decompressive surgery may have attributed to the improvement in case 1, the impact of corticosteroid therapy postoperatively likely played a role in the dog's improvement. 4 Given that the dog's ability to walk was not restored, a potentially irreversible pathological effects on the spinal cord likely had occurred.…”

“…It is possible that case 2 represents a more severe form of the sterile epidural steatitis and myositis. 2,4,5 However, the tissue gas is difficult to reconcile without concurrent anaerobic infection. The odour, gross and histological findings of the epaxial muscles were suggestive of infection with a Clostridium species.…”

“…[1][2][3] In addition to common complications of thromboembolism and local irritation at the injection site, melarsomine dihydrochloride administration has been associated with epidural steatitis, resulting in spinal cord compression and paraparesis. 2,4,5 The use of melarsomine requires strict adherence to administration protocols to minimize risk of complications. Melarsomine is injected deep into the belly of epaxial muscles between the third and fifth lumbar vertebrae.…”