Disturbances in glucose metabolism in patients with liver damage due to paracetamol overdose

1. Intravenous glucose tolerance test were performed in fourteen patients with mild or moderate liver damage due to paracetamol overdose. 2. In patients managed conservatively there was glucose intolerance associated with a diminished early insulin response to glucose, suggesting inadequate nutrition in the period between the overdose and the glucose tolerance test. 3. Patients given intravenous glucose supplements to maintain nutrition were also glucose intolerant and, in these, insulin responses to glucose were normal. The decreased fractional disappearance rate was partly due to an increase in glucose distribution space and partly due to a decrease in absolute glucose disappearance rate. 4. Impaired gluconeogenesis was suggested by mild fasting hypoglycaemia in four patients and raised fasting blood lactate concentrations. Serum growth hormone concentrations showed a paradoxical increase after glucose. 5. All these variables had returned to normal in four patients re-tested after recovery.

Hepatic glutathione depletion and impaired bromosulphthalein clearance early after paracetamol overdose in man and the rat

1. Plasma clearance of bromosulphthalein was impaired in patients within 8 h, and in rats within 2 h , of paracetamol overdose, before biochemical signs of liver damage had appeared. 2. Paracetamol and bromosulphthalein competed for uptake into the liver and excretion into the bile. Impaired hepatic uptake of bromosulphthalein could also be demonstrated in man at doses of the drug within the therapeutic range. 3. In patients studied a smaller proportion of bromosulphthalein was retained in the plasma as the glutathione conjugate after an overdose than after therapeutic doses. This effect could be reproduced in the rat and shown to be due to depletion of hepatic glutathione and to impairment in the activity of the enzyme glutathione-S-aryl transferase. 4. These studies provide further evidence that depletion of hepatic glutathione occurs after paracetamol overdose in man, as in the experimental animal, allowing the subsequent accumulation and binding of a toxic metabolite of the drug within liver cells. Impaired enzymic conjugation of the toxic metabolite with hepatic reduced glutathione may also be important in this situation.

Histopathological changes in the liver following a paracetamol overdose: correlation with clinical and biochemical parameters

The histological appearances of the liver damage occurring after a paracetamol overdose are described in liver biopsies from 104 patients, of whom 38 developed fulminant hepatic failure. Confluent centrilobular necrosis of varying extent was followed by rapid disappearance of necrotic cells, leaving areas of reticulin collapse and a usually mild inflammatory reaction. The histological recovery in even the most severe cases was remarkable, and only one of the 17 survivors whose initial biopsy showed the pattern of interlobular bridging necrosis had appreciable residual fibrosis in a follow-up biopsy taken after 1 yr. A quantitative estimate was made of the amount of surviving liver parenchyma using a morphometric technique and the hepatocyte volume fraction (HVF) in biopsies performed within 10 days of the overdose correlated well with the clinical course and both the maximal prolongation of the prothrombin time and the peak plasma bilirubin concentration in the first 10 days. An HVF value (normal 85 +/- 5 per cent.) of less than 40 per cent. in a biopsy taken within 10 days of the overdose was found only in patients who died. However, HVF measurements on biopsies from three survivors taken later than 10 days after the overdose shows that survival is possible below this critical level.

Studies with activated charcoal in the treatment of drug overdosage using the pig as an animal model

Pigs were given large oral doses of paracetamol, amylobarbitone and amitriptyline. The effect of administering activated charcoal at varying intervals after dosing on the blood drug-level profiles of paracetamol and amylobarbitone was assessed by comparison with the profiles obtained when charcoal therapy was withheld. An appreciable effect on paracetamol absorption was demonstrated when charcoal was given up to 1 h after dosing. The amylobarbitone-dosed pigs exhibited delayed gastro-intestinal absorption of drug and this was substantially reduced by activated charcoal given 4 hrs after dosing. The pigs metabolised amitriptyline at too high a rate for meaningful studies to be undertaken with this drug.

Experimental drug intoxication: treatment with charcoal haemoperfusion

Dogs were given large doses of barbiturates, glutethimide, ethanol, methaqualone, ethchlorvynol, meprobamate, chloral hydrate, paracetamol and aspirin. These were treated by haemoperfusion using a column packed with charcoal coated with an acrylic hydrogel. Clearances for most drugs were significantly higher than those reported for haemodialysis. Minimal clearances of common biochemical entities were observed and although leucocyte and platelet counts were diminished, no deleterious effects attributable to this were encountered. Careful histological examination of tissues derived from perfused dogs revealed no evidence of charcoal emboli.

Early changes in coagulation following a paracetamol overdose and a controlled trial of fresh frozen plasma therapy

Early changes in coagulation were found in patients following a paracetamol overdose. Low levels of clotting factors II, V and VII were present within 24 hours of the overdose. As the levels of factor II correlated with plasma fibrinogen values at this time, it is possible that they were consumed in the process of intravascular coagulation, although this was not supported by the presence of raised titres of fibrin degradation products. The prothrombin time ratio was greater than 2-2 within 30 hours of ingestion of the overdose in all patients who eventually died, whereas it was less than this in those developing only moderate liver damage. The administration of fresh frozen plasma to patients did appear to reduce the maximum abnormality of the prothrombin time ratio, which was significantly less three days after the overdose in the group receiving fresh frozen plasma. However, the coagulation disturbance was of short duration, and the prothrombin time ratio had also returned to normal within one week of the overdose in the control patients, and the administration of fresh frozen plasma did not appear to reduce the morbidity or mortality in the treated patients.

Effect of paracetamol on uric acid determination

The effect of paracetamol on uric acid determination using a phosphotungstate reduction method has been investigated. The results show that apparently raised values of serum uric acid may be reported in patients receiving therapeutic levels of this drug. Levels of serum uric acid were determined over a five-hour period in three patients who had received therapeutic doses of paracetamol. The assays of serum uric acid were performed by a method based on phosphotungstate reduction and by one employing uricase. The results illustrate the problems of using the former method for clinical purposes.

Acute liver injury

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Abnormal drug metabolism after barbiturate and paracetamol overdose

Drug-metabolizing capacity has been assessed by serial measurements of the plasma antipyrine half life in 11 patients with severe barbiturate intoxication and in 17 patients with acute hepatic necrosis due to paracetamol overdosage. Drug metabolism was strikingly enhanced after barbiturate over-dosage, and this effect was still present six weeks later. In contrast the antipyrine half life was greatly prolonged in patients with paracetamol-induced acute hepatic necrosis but returned to normal or near-normal values within seven to 21 days.