Clonidine interaction in amitriptyline poisoning

The effect of clonidine on amitriptyline-induced cardiotoxicity was investigated in an experimental rat mode. A continuous infusion of amitriptyline (30 mg/kg/h) was given until the animal died, usually within 2 hours. Fifteen minutes after starting the amitriptyline infusion, 50 micrograms/kg of clonidine was given intravenously over five minutes. This led to an increase in blood pressure and left ventricular end-diastolic pressure. There was no significant change in cardiac contractility. Heart rate decreased. These changes can be explained by an increase in afterload due to peripheral vasoconstriction. No signs of reduced sympathetic outflow were seen on the ECG. The peripheral effects of clonidine dominated over the central effects, which may be due to a competitive inhibition of amitriptyline at central noradrenergic sites. An increased afterload pushes the heart towards failure and increases mortality. In this model, clonidine did not reverse amitriptyline-induced cardiovascular toxicity. It may even be potentially harmful if used to treat tricyclic antidepressant poisoning.

Terbutaline concentrations in self-poisoning: a case report

A young female patient was admitted twice within two months, each time after an overdose of 500 mg terbutaline. Clinical features included nausea, tachycardia, tremor, hyperglycemia and hypokalemia. Although plasma concentrations of terbutaline were at least 50 times the normal therapeutic level, after potassium substitution the outcome was uneventful.

Role of extracorporeal drug removal in acute theophylline poisoning. A review

Theophylline, with its narrow therapeutic margin, is a common cause of iatrogenic and deliberate overdose. Most cases of self-poisoning are with sustained release preparations, with peak concentrations occurring up to 12 or more hours after overdose. Toxic symptoms are often seen at concentrations above 15 mg/L. Theophylline is metabolised within the cytochrome P-450 system, with an average total body clearance of 50 to 60 ml/min. Clearance is, however, affected by many factors such as other drugs or disease, and in overdose zero order kinetics may result in prolonged half-lives. Toxicity is characterised by agitation, tremor, nausea, vomiting, abdominal pains, seizures, and tachyarrhythmias. Hypokalaemia and metabolic acidosis are more profound in acute toxicity, and hypercalcaemia is usually present. Seizures occur at lower concentrations after chronic over-medication than after acute overdose. Gastric lavage should be performed in all patients presenting early, and an oral multiple dose charcoal regimen started with 50 to 100g charcoal, repeating with 50g doses and checking theophylline concentrations at 2- to 4-hour intervals. Multiple dose charcoal can be expected to double the clearance of theophylline, being as effective as a haemodialysis. Of the invasive techniques available, charcoal haemoperfusion is the most effective, increasing clearance 4- to 6-fold. Supportive care is particularly important. The aggressive supplementation of potassium, treatment of emesis with droperidol and ranitidine, and treatment of tachyarrhythmias and hypotension (possibly with propranolol), together with oral multiple dose charcoal may obviate the need for haemoperfusion. Seizures suggest increased morbidity and mortality. Charcoal haemoperfusion should be considered if plasma concentrations are greater than 100 mg/L in an acute intoxication or greater than 60 mg/L in a chronic intoxication. The decision to haemoperfuse should not be based on plasma concentrations alone, but an overall evaluation of the patient's laboratory and clinical status.

Does alcohol absorb to activated charcoal?

Activated charcoal seldom is used in pure-alcohol poisoning since it is absorbed rapidly from the gut. Furthermore in early reports activated charcoal was found to adsorb alcohol poorly. However, in 1981 North et al. [North, D. S., Thompson, J. D. & Peterson, C. D. (1981). Am. J. Hosp. Pharm., 38, 864-866] demonstrated in dogs that charcoal given at the same time as alcohol can reduce the blood alcohol concentration significantly. To study whether charcoal is of value in a clinical situation, a randomized cross-over study in two phases was conducted. Each person drank 88 g of alcohol and 30 min after either 20 g of activated charcoal was taken or the same volume of water was drunk. There were no significant differences in plasma alcohol concentrations with or without charcoal.

Symptoms of anxiety and depression in a volunteer twin population. The etiologic role of genetic and environmental factors

We examined the etiologic role of genetic and environmental factors in 14 symptoms of anxiety and depression reported by 3,798 pairs of adult twins from the Australian National Health and Medical Research Council Twin Register. Multifactorial multiple-threshold models fit the individual symptom scores well. For a substantial majority of the symptoms, the variance in liability was best explained by only genetic factors and environmental influences specific to the individual, where 33% to 46% of the variance was due to genetic factors. For four symptoms, it was not possible to choose definitively between models that, in addition to specific environment, included genetic vs familial environmental effects. These results provide strong evidence for the role of genetic factors in the etiology of symptoms of anxiety and depression as reported in a general population. Evidence for an etiologic role of familial environmental factors was much weaker. If familial environmental factors play any role in the production of these symptoms, they are more important in symptoms of depression than of anxiety, and the factors that predispose to these symptoms are only modestly correlated in males and females.

Haemoperfusion: a useful therapy for a severely poisoned patient?

Although it is many years since a haemodialysis and haemoperfusion over uncoated and later coated charcoal columns have been used for the treatment of intoxicated patients, the clinical efficacy of these extracorporeal techniques in the treatment of severely poisoned patients remains a matter of debate. Some of the reasons for this controversy may be the indiscriminate use of haemoperfusion in any form of intoxication, the lack of well-controlled studies and the wrong interpretation of the high haemoperfusion clearance values sometimes obtained. Simple pharmacokinetic principles are applied to this type of treatment and some practical guidelines as to how and when haemoperfusion should be applied or presented are reviewed. The limited place of haemoperfusion in the treatment of severe poisoning, its further declining use in the future, at least in its present design, and some promising new treatments are emphasized.

Beta-adrenoceptor blocker toxicity: clinical features and therapy

Therapy for severe beta-blocker poisoning should be based upon careful supportive therapy. In most cases of poisoning, elimination techniques cannot be expected to remove significant amounts of the drug. Inotropic drugs such as isoproterenol, prenalterol and glucagon in adequate (i.e. large) doses may be necessary to counteract cardiac failure.

Inotropic effect of prenalterol in amitriptyline poisoning

A case of severe amitriptyline poisoning with grade IV coma, seizures, bradycardia and hypotension who did not respond to dopamine was successfully treated with prenalterol, a new cardioselective beta-agonist. The case is discussed with respect to plasma concentrations of dopamine, prenalterol and amitriptyline. Prenalterol, hydrocortisone and insulin may be useful as inotropic agents in tricyclic poisoning where dopamine fails to provide an adequate response.

Lidocaine and amitriptyline interaction during experimental haemoperfusion

Displacement of amitriptyline by lidocaine was studied during haemoperfusion (HP) in five beagle dogs. Clearance of amitriptyline during HP was 0.93, although the amount of amitriptyline removed was only 2% of the given dose. Lidocaine does therefore not improve amitriptyline yield during HP. Clearance of lidocaine during HP was 0.99. Almost 13% of the lidocaine given intravenously was removed by HP. Lidocaine did not improve myocardial performance during HP in amitriptyline-intoxicated dogs. At necropsy the highest concentrations of amitriptyline in this model were found in the brain and the lung. The amitriptyline/nortriptyline ratio was lowest in the liver and lung, suggesting that these two organs are major sites of metabolism.

Effects of self poisoning with maprotiline

Self poisoning with maprotiline was studied in 41 patients (43 episodes) consecutively admitted to an intensive care unit. Thirty five patients had taken more than one drug or alcohol. Fifteen patients were in coma grade III or IV; 17 patients were still not conscious after 24 hours in the intensive care unit. Among six patients given ventilation the mean duration of ventilation in the five who recovered was 36 hours. Three patients had a cardiorespiratory arrest, and one patient died. Twenty eight patients had a QRS interval of 100 ms or more, and 15 patients had seizures. In six patients seizures were precipitated by physostigmine. Cardiotoxicity after overdosage of maprotiline is equal to if not greater than that found after overdosage of conventional tricyclic antidepressants. Overdosage of maprotiline is more often associated with seizures than overdosage with tricyclic antidepressants. Physostigmine further increases the risk of seizures and should not be used in cases of overdosage of maprotiline.

Elimination methods in neurotoxicology

In addition to supportive care and, if appropriate, antidote therapy, the prognosis in some poisonings can be improved by increasing drug or toxin elimination. Such methods include peroral activated charcoal, forced diuresis, peritoneal and hemodialysis, and hemoperfusion. The choice of method should be based upon a knowledge of the pharmacology of the drug or toxin itself and the limitations of the technique employed. This review focuses on the pharmacological principles involved, outlining the limitations and indications for these techniques in toxicology.

Thallium poisoning--toxin elimination and therapy in three cases

Three cases of thallium poisoning occurred within the same family after eating a meal of poisoned sour milk. The 58 year old mother died after four days cardiovascular insufficiency. Massive thallium concentrations were found in blood, urine, liver and kidney. The 59 year old father presented after four days with a neurology typical for classic thallotoxicosis with potentially lethal blood thallium levels. This patient recovered after therapy including Prussian Blue, forced diuresis and two six hour hemoperfusions with a charcoal column. Urinary elimination of thallium over two weeks was almost 300 mg, whereas a maximum total of 63 mg were removed with hemoperfusion. A retrospective estimate of the total dose ingested and the large distribution volume of thallium suggest that hemoperfusion did not affect the course of the intoxication. The 28 year old son, later convicted for homicide, was admitted on the tenth day after the meal with very discrete neurological symptoms. This patient had low blood and urine thallium levels. He recovered uneventfully after treatment with Prussian Blue and forced diuresis. However, both surviving patients developed alopecia after two weeks. All three patients had raised liver transaminases. Intensive therapy with gut decontamination, Prussian Blue and forced diuresis should be the mainstay of therapy.

Absorption of beta-adrenoceptor antagonists to Amberlite resin

The adsorption of beta-adrenoceptor blockers and the partial beta-adrenoceptor agonist prenalterol was studied in an in vitro haemoperfusion (HP) model. Metoprolol, alprenolol, propranolol and prenalterol adsorb well from the blood to the resin with extraction ratios nearing 1.0. Extraction ratio for practolol was 0.68 and for atenolol 0.49. Protein binding has little effect on the degree of adsorption, which is more dependent on water solubility.

Resin hemoperfusion in chloroquine poisoning

A 46-year-old woman was admitted after ingestion of 10 g chloroquine phosphate. The patient's clinical condition deteriorated with characteristic ECG changes, low blood pressure, and respiratory depression. Resin hemoperfusion (HP) was started 4.5 h after admission at a flow of 250 mL/min for 4 h. Clearance over the resin column was 136 mL/min. Although the patient rapidly improved, a total of no more than 200 mg (2%) was removed. Total body clearance of chloroquine was increased by only 5% during HP. Treatment should therefore be directed toward aggressive supportive therapy rather than techniques to increase elimination.

Treatment of antidepressant poisoning with resin hemoperfusion

1 The object of this study was to evaluate hemoperfusion in tricyclic antidepressant (TCA) poisoning. 2 Eight patients with severe TCA-poisoning and one patient with maprotiline poisoning were treated with resin hemoperfusion (HP). All patients were in Grade III or Grade IV coma with a QRS interval of 100 ms or greater. Hemoperfusion was started and continued until a satisfactory clinical response was obtained or for up to a maximum of 4 h. 3 Clearance values and extraction ratios were calculated during HP. The extraction ratio for all drugs was high (0.91-0.98) showing an effective clearance of these drugs from the blood compartment. After termination of HP a rebound effect of blood concentrations was seen in five cases. The total amount of the drug recovered was in no case greater than 3.1% of the estimated amount ingested. 4 It is therefore difficult to ascribe the clinical improvement seen in these patients during HP to the removal of significant amounts of the drug taken.

Treatment of podophyllin poisoning with resin hemoperfusion

1 A 43-year-old man was admitted in a coma after oral ingestion of a suspected lethal dose of podophyllin solution in alcohol. 2 Hemoperfusion with a resin filter was started 7 h after ingestion. Hemoperfusion rapidly decreased plasma concentrations of podophyllotoxin with an extraction ratio of 0.76 over the filter. The relatively low plasma concentrations of podophyllotoxin and consequently small amount removed might be explained by the rapid metabolism of the drug to an unknown derivate. 3 This metabolite was completely cleared during passage over the filter, suggesting the removal of significant amounts of podophyllotoxin metabolites. 4 No neurological deficit was observed before or after hemoperfusion. At a two-month follow-up the patient remained healthy. Hemoperfusion may possibly prevent the development of coma and neurologic deficit with loss of deep tendon reflexes.

Increased platelet aggregation induced by glucagon administration

The effect of 1 mg of intravenous glucagon on platelet aggregation has been investigated in 12 normal subjects pre-treated with salicylate. All subjects demonstrated the expected inhibition of collagen-induced secondary aggregation but retained the normal adenosine diphosphate (ADP)-induced primary aggregation phase 18 h after the salicylate therapy (600-1,200 mg). Subsequent administration of glucagon caused a significant increase in the ADP-induced primary aggregation phase in the 12 subjects. This data indicates that glucagon increases the reactivity of platelets to ADP and may help to explain the common clinical association of raised plasma glucagon, increased platelet aggregation and vascular disease.

Anticonvulsants and thyroid function

Serum total and free thyroid hormone concentrations were estimated in 42 patients with epilepsy taking anticonvulsants (phenytoin, phenobarbitone, and carbamazepine either singly or in combination). There was a significant reduction in total thyroxine (TT4), free thyroxine (FT4), and free triiodothyronine (FT3) in the treated group compared with controls. Free hormone concentrations were lower than total hormone concentrations, suggesting that increased clearance of thyroid hormones occurs in patients receiving anticonvulsants. Detailed analysis indicated that phenytoin had a significant depressant effect on TT4, FT4, FT3, and reverse T3 (rT3). Phenobarbitone and carbamazepine had no significant main effects, but there were significant interactions between phenytoin and carbamazepine for TT4 and FT4. phenobarbitone and carbamazepine for FT3, and phenytoin and phenobarbitone for rT3.

Patterns of family building and contraceptive use of middle-class couples

Interviews with 103 middle-class wives on their family building experiences and use of birth control techniques show this highly educated group to be effective family planners in comparison with other social groups. The wives developed clear ideas early in marriage about family size, timing and spacing, formulated with reference to sets of beliefs about the transmission of cultural advantage from parents to children, and their social responsibility in relation to world population levels. Ideas about the spacing of children and desired family size appear to be influenced by the women’s orientation towards returning to employment, but their relatively late age of terminating full-time education has had remarkably little effect on the timing of either marriage or the first child’s birth. Female contraceptive methods were most popular with this sample, and their relative effectiveness as family planners may be explained by their preference for the more reliable techniques and high level of motivation to use them efficiently. Variations in patterns of contraceptive usage noted between this and other studies are probably a function of age differences in the groups of women surveyed.