Experimental study of the detrimental effect of dopamine/glucagon combination in d,l-propranolol intoxication.

1. Respiratory and cardiovascular failure are the principle toxic effects of beta-blocker overdose. Respiratory arrest is the primary cause of death in beta-blocker intoxicated rats. 2. The effect of glucagon, dopamine and the combination of glucagon/dopamine on respiratory and cardiovascular function and survival time in beta-blocker overdose was investigated in a model of acute d,l-propranolol (resp. 30 and 15 mg kg-1 h-1 in rat and rabbit) intoxication in spontaneously breathing rats and artificially ventilated rats and rabbits. 3. Glucagon (initial dose of 100 micrograms kg-1 (bolus), followed by 1 microgram kg-1 min-1), dopamine (25 micrograms kg-1 min-1) or the combination of glucagon/dopamine did not improve survival time (ST) in d,l-propranolol intoxicated spontaneously breathing rats and artificially ventilated rats and rabbits, although some haemodynamic variables i.e. heart rate (HR), mean arterial blood pressure (MAP), left ventricular pressure (LVPmax) and the differentiated left ventricular pressure (LVdp/dtmax) temporarily improved. 4. Survival time was considerably reduced in d,l-propranolol intoxicated spontaneously breathing and artificially ventilated rats treated with a combination of glucagon/dopamine, which induced a decrease in PaO2 and pH and an increase in PaCO2 partly due to ventilation/perfusion mismatch. 5. The combination of glucagon/dopamine should be used carefully in the treatment of beta-blocker overdose in man.

Reduced survival after isoprenaline/dopamine in d,l-propranolol intoxicated rats.

1. Respiratory and cardiovascular failure are principle toxic effects of beta-blocker overdose. Respiratory arrest is the primary cause of death in beta-blocker intoxicated rats. 2. The effect of beta-adrenoceptor agonists on respiratory and cardiovascular failure in beta-blocker overdose was investigated in a model of acute d,l-propranolol (30 mg kg-1 h-1) intoxication in spontaneously breathing rats. 3. Neither the aselective, hydrophilic beta-agonist isoprenaline (10, 25, 50 micrograms kg-1 min-1), nor the beta 1-selective, lipophilic beta-agonist flerobuterol (1, 3, 10 microgram kg-1 min-1) and the beta 2-selective, lipophilic beta-agonist clenbuterol (10, 25, 50 micrograms kg-1 min-1) had any beneficial effect on cardiovascular and respiratory variables or survival time in d,l-propranolol intoxicated spontaneously breathing rats. 4. Isoprenaline (10 micrograms kg-1 min-1) had no favourable effect on haemodynamic and respiratory variables in artificially ventilated d,l-propranolol intoxicated rats either. 5. Addition of dopamine to isoprenaline resulted in a significant reduction of survival time, primarily caused by a decreased in mean arterial blood pressure, in artificially ventilated d,l-propranolol intoxicated rats. Addition of glucagon to isoprenaline did not affect survival time. 6. Artificial ventilation is the most important supportive measure in d,l-propranolol intoxication in the rat.

Toxic doses of rac-, (-)-(S)- and (+)-(R)-propranolol in rats and rabbits.

The contribution of the individual enantiomers ([+]-[R]- and [-]-[S]-propranolol) to rac-propranolol intoxication was studied in anaesthetized, spontaneously breathing (SB) rats and artificially ventilated (AV) rats and rabbits. In the SB rat, propranolol (30 mg.kg-1.h-1 i.v.) decreased heart rate and mean arterial blood pressure and caused hypoventilation, serious hypoxaemia, respiratory acidosis, and death by respiratory arrest. Survival time (ST) in the (+)-(R)-propranolol group (ST 91 +/- 5 min) was significantly longer than in the rac-propranolol group (ST. 68 +/- 6 min). In AV rats and rabbits toxic doses of rac-, (-)-(S)- and (+)-(R)-propranolol, 30 mg.kg-1.h-1 and 15 mg.kg-1.h-1 i.v., respectively, induced comparable effects on haemodynamic variables as in the SB rat. Artificial ventilation lengthened ST by a factor of three to four in rats. In the AV rat, ST's were not significantly different between the rac-, (-)-(S)- and (+)-(R)-propranolol groups. In the rabbit, as in the SB rat, ST in the (+)-(R)-propranolol group was significantly longer than ST's in the rac- and (-)-(S)-propranolol groups. The acute respiratory acidosis in SB rats and the prolonged ST in AV rats suggest that respiratory failure is the primary and cardiovascular failure the secondary cause of death in propranolol intoxication. The potentiation of the toxic effect of the enantiomers observed after dosing the racemate instead of the pure enantiomers could not be explained by a stereoselective difference in plasma propranolol concentration.

Toxicokinetics of a single intravenous dose of rac-propranolol versus optically pure propranolol in the rat.

Conscious male Wistar SPF Riv:TOX rats were dosed intravenously with 2.5, 5, or 10 mg/kg rac-propranolol.HCl, or with 5 mg/kg of either (-)-(S)- or (+)-(R)-propranolol.HCl. Disposition of (-)-(S)- and (+)-(R)-propranolol after dosing of rac-propranolol was linear in the dose range examined. Total plasma clearance was not changed in animals dosed with the individual enantiomers compared to the animals that were dosed with rac-propranolol. However, for (-)-(S)-propranolol both volume of distribution and elimination half-life decreased, whereas for (+)-(R)-propranolol increases were observed for these characteristics, in animals dosed with the individual enantiomers. Our observations suggest that the (+)-(R)-enantiomer competes with (-)-(S)-propranolol for plasma protein binding sites, resulting in lower plasma protein binding of the (-)-(S)-enantiomer when the racemate is administered. From recent toxicological experiments, it was concluded that rac-propranolol is more toxic than the individual enantiomers in the rat, when dosed iv at the same total mass. It is concluded that the observed potentiation of toxic effects of propranolol enantiomers when administered as a racemate can at least partly be explained by a pharmacokinetic interaction.

Mercury kinetics in a case of severe mercuric chloride poisoning treated with dimercapto-1-propane sulphonate (DMPS).

A case of severe mercuric chloride poisoning with clinical signs of mucosal damage of the gastrointestinal tract and anuric renal failure, is presented. The initial whole blood mercury concentration was 14,300 micrograms l-1. This concentration is supposed to be associated with fatal outcome due to multiple organ failure. Because of anuric renal failure, haemodialysis was necessary. Kidney function returned to normal within 10 days. Haemodialysis proved to be ineffective with regard to total mercury elimination. Treatment with DMPS was started because of very severe poisoning, anuric renal failure and optimistic reports on the "new" chelating agent 2,3-dimercapto-1 propanesulphonic acid (DMPS) in mercury poisoning. DMPS was administered by parenteral route initially and was continued thereafter by oral route, until whole blood and urine mercury concentrations had decreased below a level considered as toxic. Except for a temporary pruritic erythema of the skin, no side effects of DMPS treatment were observed. The clinical course was mild, despite continuing high whole blood mercury concentrations. Recovery was uneventful and complete. DMPS treatment, administered by intravenous and oral route, was shown to be an effective alternative for BAL in life-threatening mercuric chloride intoxication. The pharmacokinetic data presented in this case report suggest that non-renal mercury clearance may considerably exceed renal mercury clearance.

Anaphylaxis as a rare complication of a barium enema examination.

A patient is described who developed anaphylaxis with respiratory and circulatory arrest after a single contrast barium enema examination. Since barium sulphate is an inert substance, the reaction must have been caused by additives present in the barium suspension.