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Detomidine is an alpha-2 adrenoceptor agonist drug, which is used in veterinary medicine for sedation of large animals.1–4 It is highly potent and has sedative and analgesic properties.1,2 This paper reports a case of accidental human poisoning with this drug.
A 35 year old farmer was preparing to sedate a bull in order to pare its hooves. No vet was present. The farmer had 5 ml of Domosedan (detomidine hydrochloride 10 mg/ml) in a 5 ml syringe with a 21G×1.5″ (0.8×40 mm) needle attached. The bull moved as the farmer was about to give this medication and he injected himself in the thenar emminence of his left hand. He later said that he had been holding the syringe by the barrel rather than the plunger and he did not think he had injected a significant volume of the drug. He claimed that he could not recall how he came to possess the drug. He had no relevant medical history, was on no medication, and had last drunk alcohol 4 days previously.
Within 10 minutes of this accident, the farmer began to feel drowsy, dizzy, and relaxed. His companions noted that he was not performing his tasks normally. When questioned, he responded in a slurred and drunken manner. His gait became unsteady. He was carried to a vehicle and taken to the emergency department.
On arrival he was noted to be drowsy, with slurred speech, and a passively euphoric state, but his Glasgow Coma Score (GCS) was 15. His heart rate was 44 beats/min and his blood pressure 106/48 mmHg. A small superficial puncture wound was noted on the left thenar emminence. No other abnormality was apparent on examination. His ECG showed a sinus bradycardia with no evidence of heart block or ischaemia.
Peripheral intravenous access was obtained and an infusion of 0.9% sodium chloride was started. Two boluses of atropine 500 μg were given. Within minutes, a sustained rise in heart rate and blood pressure was noted, but the patient remained significantly drowsy. He was given 2 litres of intravenous saline over 2 hours. TOXBASE (an online poisons database; www.spib.axl.co.uk) was consulted. The patient was observed overnight with cardiac monitoring but received no further medications. Over the next 16 hours he regained full consciousness and his pulse and blood pressure remained normal. He was discharged home.
Detomidine (trade names Domosedan and Dormosedan) is used for sedating horses and other animals to facilitate examination and surgical procedures.1,2 Detomidine causes a bradycardia with blood pressure initially raised and then normal or low, reduced cardiac output, and slowing of intracardiac conduction with partial sinoatrial and atrioventricular block. Respiratory depression and diuresis may occur.1,2 Detomidine potentiates the actions of other sedative and analgesic drugs. It has similar effects to clonidine.5–7
TOXBASE (www.spib.axl.co.uk/toxbase/poisons%20information/d/detomidine.htm) mentions that a dog that chewed a vial of detomidine had salivation, sedation, collapse, hypotension, bradycardia, arrhythmias, and coma, which lasted for 18 hours. The treatment advised by TOXBASE in human poisoning is supportive, with observation for at least 4 hours, or longer if symptomatic, and monitoring of blood pressure and cardiac rhythm. Hypotension should be corrected by raising the foot of the bed and by giving intravenous fluids, and vasopressors should be considered in severe cases. Bradycardia may require treatment with atropine and rarely with cardiac pacing. Severe and persistent hypertension may be treated with phentolamine.
The only previous report of detomidine poisoning in humans is a single case of deliberate injection of detomidine 50 mg and butorphanol 100 mg in a 36 year old man.8 Butorphanol is an opioid drug for which the antidote is naloxone.9 The patient presented with a GCS of 6 and required a continuous infusion of naloxone, but his heart rate never fell below 70 beats/min and his blood pressure never below 110/80 mmHg. He made a full recovery.
The manufacturers of detomidine are aware of only one other case of human exposure to this drug (Pfizer, personal communication). In this case, the farmer rapidly developed sedation and had bradycardia and hypotension but recovered with the treatment advised by TOXBASE.
Detomidine is a potent drug and the dose recommended for sedation and analgesia in animals is 20 to 40 μg/kg that is, 0.2–0.4 ml/100 kg.1 In this case the syringe contained 5 ml, which would have been sufficient for an animal of at least 1500 kg. It was fortunate that only a small amount was apparently injected. The farmer believed that only the drug that was in the needle was actually injected, but this could not be confirmed. A larger volume might have caused catastrophic cardiovascular collapse.
Detomidine should only be used by veterinary surgeons. The unregulated use of such potent drugs by non-veterinary personnel is hazardous. In this case, the farmer was unwilling to say how he came to have this restricted medication, and this raises issues about the availability of this and other veterinary drugs. One might wonder whether some fatal farmyard accidents could result from unrecognised exposures to potent veterinary medications.10
Competing interests: none declared