Asystole complicating physostigmine treatment of tricyclic antidepressant overdose

Physostigmine is a commonly used therapy for the anticholinergic manifestations of tricyclic antidepressant (TCA) overdose. We describe two patients with TCA toxicity who developed asystole following the administration of physostigmine to treat seizures.

Tricyclic antidepressant poisoning in children

The MR images, CT scans, and angiograms of 15 consecutive patients with intracranial, supratentorial arteriovenous malformations (AVMs) were studied retrospectively. The three imaging techniques were evaluated separately to assess their utility in defining the size, characteristics, and location of the AVM nidus, its arterial supply, and venous drainage. The studies were also evaluated for their ability to show associated parenchymal abnormalities, the presence of mass effect, and changes occurring after embolization. MR was superior to both CT and angiography in showing the exact anatomic relationships of the nidus, feeding arteries, and draining veins, as well as in demonstrating the extent of AVM nidus obliteration after embolization. MR was more sensitive than CT in revealing associated parenchymal abnormalities and subacute hemorrhage. Because of flow-related artifacts and low sensitivity in distinguishing calcification from rapid flow and/or hemosiderin, MR seemed to have a low sensitivity for detecting old hemorrhage within an AVM nidus. Angiography is still needed in the planning of either surgical or endovascular treatment of AVMs.

Magical thinking and imipramine poisoning in two school-age children

Two young school-aged boys took an overdose of imipramine hydrochloride to help their enuresis. One child died, and the other required resuscitation. An office survey found that one third of school-aged children did not realize the potentially hazadous consequences of taking extra amounts of prescription medications. Physicians might be able to prevent similar needless tragedies by warning both the child and the parents of the unusual lethality of imipramine and other dangerous prescription drugs.

Nonaccidental poisoning in childhood

A boy aged 7 years 10 months was admitted to hospital on several occasions in an unconscius state with twitching and apnoeic episodes. Initial investigations failed to show a specific cause. During his time in hospital he had recurrent episodes of loss of consciousness and, on the last occasion, hypotension and ventricular tachycardia. A diagnosis of imipramine poisoning was established by the presence of imipramine in stomach washings and blood. The drug was being given to the child, both at home and in hospital, by his mother. The possibility of nonaccidental poisoning must be considered if there is no obvious cause for a child's illness. In this case the mother responded to psychiatric treatment.

ECG changes in pure impramine overdose as function of plasma level

ECG changes occur with therapeutic doses of tricyclic antidepressants and cardiovascular conduction alteration is the lethal effect in overdoses on these drugs.

These ECG changes depend on the plasma level and metabolism of the particular antidepressant. Information about the relative toxicity and metabolism characteristics can be obtained by studying overdoses if the attempt simply involves one tricyclic and no other drug ingestion. Such a case report involving a known quantity of imipramine is presented.

The early toxic signs leading to cardiac arrest and the recovery from coma are discussed. The ECG along with corresponding plasma levels of imipramine and its metabolite desmethylimipramine are given as a function of time after ingestion. The relative toxicity of these metabolites and the use of anticholinesterase in the acute management is considered.

Tricyclic antidepressants: plasma levels and clinical findings in overdose

Following amitriptyline or imipramine overdose by 30 patients, total plasma concentrations ranged from 29 to 1732 ng/ml but did not correlate well with physical findings or most electrocardiographic changes. Only those patients with a QRS interval greater than 0.1 second had significantly elevated plasma levels. However, a plasma level ratio of the parent drug (amitriptyline, imipramine) to its respective N-desmethyl metabolite (nortriptyline, desmethylimipramine) greater than or equal to 2.0 was associated with an acute overdose. This ratio was more useful than total plasma levels in differentiating an overdose from a therapeutic dose with associated toxicity and an elevated steady-state plasma level.

[The use of direct and indirect parasympathomimetics in poisonings with tricyclic antidepressive agents]

The use of cholinesterase inhibitors in poisonings with potentially lethal doses of tricyclic antidepressive drugs seems to be indicated on account of clinical experiences and own experimental investigations on animals. An uncritical use of these substances which have considerable side-effects must be warned of. A mixed intoxication with several drugs effecting on the central nervous system is only a relative indication for the use of indirect parasympathicomimetics of the cholinesterase type. They should be used only then, when the picture of poisoning is unequivocally determined by the thymoleptics. When cholinesterase inhibitors are used the physostigmine salicylate should be preferred, since at present it is sufficiently accessible to the central nervous system and with the slightest peripheral effects as the only representative of this group of substances, above all with regard to the gastrointestinal motility. Later investigations shall show, whether also other groups of substances which develop an antagonistic effect to the tricyclic antidepressive drugs may be of use in the treatment of the acute poisoning.

Effects of phenobarbital and diazepam on imipramine-induced changes in blood pressure, heart rate and rectal temperature of rats

To investigate the safety of anticonvulsants in doses found equipotent in suppressing imipramine induced convulsions, the effects of diazepam (1.8 mg/kg) or phenobarbital (40 mg/kg) following a toxic dose of imipramine (50 mg/kg) on heart rate, blood pressure and body temperature were examined in male Wistar rats. Administration of imipramine alone resulted in significant decreases in blood pressure, heart rate and rectal temperature. Phenobarbital or diazepam alone failed to significantly affect any of these parameters apart from a slight reduction in rectal temperature seen with phenobarbital. Diazepam given after imipramine antagonized the imipramine-induced decrease in heart rate but increased the hypotensive and hypothermic effects. Phenobarbital failed to significantly affect the imipramine-induced changes in any of the physiological parameters studied. The present data suggests that phenobarbital may be preferable to diazepam in treatment of imipramine-induced convulsions.

Lipid hemodialysis versus charcoal hemoperfusion in imipramine poisoning

Previous experimental results have demonstrated the possibility of eliminating imipramine (14 C-IP) by hemodialysis. A simultaneous uptake of the substance by the polyvinyl chloride extracorporeal blood lines could be shown. Based on these results the imipramine absorption capacity of the blood lines and of the artificial kidney (Hollow Fiber Artificial Kidney, HFAK, Model 4) were studied. Imipramine (IP) absorption capacity of a usual blood-line set (arterial and venous, surface area 86,000 mm) was estimated to be 43 mg, and that of the HFAK to be 207 mg. Charcoal hemoperfusion (300 gm of coated activated coconut charcoal) eliminated more than 90% of IP from the blood within 3 hr if the initial IP blood concentration was 2 mg/ml. In comparison, lipid hemodialysis using 20% soybean oil as dialysate eliminated 95% of IP from the blood when the initial IP blood concentration was 1 mg/ml and 98% when the initial IP blood concentration was 2 mg/ml. In vivo studies on the elimination of IP by lipid (10%) hemodialysis demonstrated a substantial removal of the substance. Within 2 hr of treatment, 12% of the administered dose (75% of the LD50) was eliminated.

Tricyclic antidepressant overdose: incidence of symptoms

Forty consecutively hospitalized patients who had overdosed primarily with a tricyclic antidepressant (TCA) were observed until discharge. The severity of the overdose was documented by serial measurements of plasma TCA levels. Nineteen of the patients became comatose, 16 required supportive respiration, and 2 died. Individual symptoms in the 13 patients having plasma TCA levels greater than 1,000 ng/ml are shown. Plasma TCA measurements more reliably define patients who are at risk for major medical complications following overdose than does the amount of drug ingested by history. In the absence of plasma measurements, a QRS duration of 100 msec or more on a routine ECG within the first 24 hours defined all patients with major TCA overdoses.

Imipramine (Tofranil) intoxication: a case report and review of management

A fatal case of imipramine intoxication is reported. The patient presented with the typical findings of imipramine poisoning: coma, fixed dilated pupils, cardiac disturbances, and hyperpyrexia which, at first, were attributed to head trauma. The importance of prompt recognition of such poisoning is emphasized, and a general scheme of treatment is outlined.