Use of neostigmine in massive ivermectin toxicity in cats

Over-the-counter availability of drugs in developing countries poses the risk of their abuse and overdosing in animals by the owners. This report describes ivermectin toxicosis and its treatment with neostigmine methylsulfate in 2 kittens and an adult cat that had been massively overdosed by their owners. Of two 4-w-old 300 g kittens, one was injected with 1.5 ml ivermectin (15 mg; corresponding to 250 times the recommended dose) by the owner and became comatose, started salivation and died after 2 1/2 h. The other kitten was treated with about 0.75 ml ivermectin (7.5 mg; corresponding to 125 times the recommended dose) by the same owner and developed ataxia and salivation after 2 h, went into coma the next morning and was presented for treatment with mydriasis, coma, slight fever (102.4 F), tachypnea (48/min) and severe tachycardia. This kitten was treated twice at a half hourly interval with neostigmine methylsulfate (25 microg) and 5% dextrose (20 ml) iv showed a transient improvement but died 12 h later. A 2-y-old, 4.5 kg male cat was treated s.c. with 1.5 ml ivermectin (15 mg; corresponding to 16.6 times the recommended dose) by its owner and developed slight salivation, lacrimation. mydriasis, protrusion of third eye-lid, tachypnea (42 breaths/min), tachycardia (128 beats/min) and ataxia. The patient was treated with neostigmine methylsulfate (150 microg) and 5% dextrose (100 ml) i.v., and 200 ml of Heartmann's solution i.v. Treatment was repeated after 6 h Follow up treatment over next 2 d was with daily i.v. administration of neostigmine and dextrose. The patient completely recovered 5 d after initiation of treatment.