The effects of meperidine and morphine in rabbits pretreated with phenelzine

Drug interactions with intravenous and local anaesthetics

Relatively few clinically significant drug interactions with anaesthetics have been documented in the literature. The following should be stressed since these interactions are not readily predictable or are potentially fatal. Pethidine should never be administered to patients who have received monamine oxidase inhibiting drugs within the last fortnight, since a fatal hyperpyrexia and/or hypertension may result. Thiopentone induction seems to make the heart more susceptible to arrhythmias caused by adrenergic drugs, and may cause severe arterial hypotension in patients treated with diazoxide. Midazolam orally should possibly be avoided as premedication in patients treated with erythromycin since anaesthetic concentrations of midazolam may result. Patients for whom bupivacaine analgesia is planned could preferentially be premedicated with other drugs than diazepam, which causes the serum level of bupivacaine to increase. Bradycardia and hypotension not attributable to sympathetic blockade have been reported following bupivacaine extradurally in verapamil-treated patients. Sulfonamides and the ester group of local anaesthetics, such as prilocaine in combination, may result in severe methaemoglobinaemia in infants. Epinephrine added to local anaesthetics may cause local vasodilation if administered to patients concurrently being treated with cyclic antidepressants, and the combination imposes the risk of severe hypertension and arrhythmias.

Interaction of butorphanol, with monoamine oxidase inhibitor, tranylcypromine

This investigation examines the possibility of interaction between tranylcypromine and butorphanol in comparison to pethidine. The LD50 of pethidine and butorphanol were determined in mice pretreated with the non-selective monoamine oxidase (MAO) inhibitor, tranylcypromine orally for 8 days or with oral saline solution. Tranylcypromine decreased the LD50 of both pethidine and butorphanol by 78% and 41%, respectively. Anesthetized rabbits with halothane pretreated with tranylcypromine or saline were given pethidine (5 mg/kg i.v.) or butorphanol (0.5, 1 and 2 mg/kg i.v.). Pethidine produced a marked increase in blood pressure in rabbits pretreated with tranylcypromine and did not affect significantly the heart rate. Butorphanol did not affect either blood pressure or heart rate at doses of 0.5 or 1 mg/kg. However, the largest dose of butorphanol (2 mg/kg) produced hypotension and tachycardia in rabbits pretreated with tranylcypromine. Neither pethidine nor butorphanol affected the temperature of anesthetized rabbits pretreated with tranylcypromine or saline.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants

This survey, the third in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of adrenergic and serotonergic agonists and their antagonists including ergot alkaloids, amphetamines, tryptamines, monoamine oxidase inhibitors, tricyclic and other antidepressants, a variety of other agents which alter presynaptic aminergic mechanisms including reserpine, 6-hydroxydopamine, p-chlorophenylalanine, alpha-methyltyrosines, cocaine, guanethidine and bretylium. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug.

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents

This survey, the second in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of cholinergic agonists and antagonists, histamine and H1- and H2-receptor antagonists, narcotic analgesics and antagonists in both non-tolerant and tolerant subjects and of prostaglandins and related agents. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug.

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents

Drugs may alter body temperature by acting on any component of the thermoregulatory system. These components include heat production, heat conservation and heat loss effectors and their efferent pathways, thermosensors and their afferent pathways and neurons within the central nervous system that coordinate thermoregulatory effector activities. A thermostat is often thought to be involved although thermoregulation can be explained by models that do not incorporate a thermostat. An action on a particular component can be assessed by determining the effect of a drug on body temperature over a range of environmental temperatures and by observation and measurement of associated changes in effector activities. A scheme for such assessment is presented along with examples of its use. The study of drug-induced changes in body temperature has expanded greatly within the past decade. The primary purpose of this review is to provide a readily available source of information on interactions between certain drugs and the thermoregulatory system. Extensive tables are presented of body temperature changes after administration of amino acids, peptides, dopamine and related agents, phenothiazine neuroleptics and also phenothiazines that lack neuroleptic activity, butyrophenones, diphenylbutylpiperidines such as pimozide and miscellaneous neuroleptics. The information tabulated includes the species used, route of administration and dose of drugs, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug. Most of the cited literature was published since 1965.

Hyperpyrexic interaction between debrisoquine and pethidine in rabbits

Pethidine injection into rabbits treated with debrisoquine either acutely or chronically resulted in severe interaction and fatal hyperpyrexia. Pretreatment of rabbits with p-chlorophenylalanine, chlorpromazine, or crypoheptadine protected them against the interaction, while alpha-methyl-p-tyrosine was ineffective. In addition the administration of debrisoquine into 5-HTP pretreated rabbits produced a severe interaction and hyperpyrexia. The hepatic N-demethylation of pethidine was significantly inhibited by debrisoquine pretreatment both in vivo and in vitro. The debrisoquine-pethidine interaction could be due to 5-HT potentiation or prevention of uptake. Alternatively it could be due to inhibition of biotransformation of pethidine by debrisoquine. However, neither mechanism by itself alone could be held responsible as the sole explanation of the interaction.

Furazolidone-pethidine interaction in rabbits

1 The intravenous injection of pethidine in rabbits pretreated with furazolidone administered orally but not systemically resulted in severe interaction and fatal hyperpyrexia. 2 Treatment with rho-chlorophenylalanine, chloropromazine of cyproheptadine protected the rabbits against the furazolidone-pethidine interaction, while alpha-methyl-rho-tyrosine was ineffective. 3 5-Hydroxytryptophan produced a fatal hyperpyrexia in furazolidone pretreated rabbits. 4 Pretreatment of rabbits with 1,1,1-trichloro-2, 2-bis(rho-chlorophenyl)ethane (DDT) accelerated and enhanced the furazolidone-pethidine interaction, while oxytetracycline pretreatment completely prevented the interaction. 5 It is concluded that furazolidone-pethidine interaction might depend mainly on potentiation of the effects of 5-hydroxytryptamine in the CNS and that the transformation of furazolidone into an active monoamine oxidase inhibitor metabolite might occur mainly in the gut microflora in the gut lumen.

Dextromethorphan-monoamine oxidase inhibitor interaction in rabbits

Severe toxic reactions may occur clinically when imipramine, pethidine or dextromethorphan is administered to a patient being treated with a monoamine oxidase inhibitor (MAOI). Previous reports indicate that imipramine or pethidine produces symptoms characterized by motor restlessness, tremor, extreme hyperpyrexia and death when administered to phenelzine-pretreated rabbits. The present study shows that dextromethorphan (5 mg kg−1) produces identical symptoms in rabbits pretreated with phenelzine sulphate (30 mg kg−1) or nialamide HCl (50 mg kg−1) 42 and 18 h before temperature recording. The dextromethorphan-MAOI interaction appears to be due to a 5-hydroxytryptamine potentiation. In the unanaesthetized cat nictitating membrane preparation, dextromethorphan (5 mg kg−1) markedly enhanced the response of noradrenaline and 5-HT but antagonized the effects of tyramine. This suggests that dextromethorphan blocks the uptake of these amines in the adrenergic nerve endings.

Role of brain monoamines in the fatal hyperthermia induced by pethidine or imipramine in rabbits pretreated with a monoamine oxidase inhibitor

1. The intravenous infusion of pethidine or imipramine, in doses of 5 mg/kg, caused fatal hyperpyrexia in rabbits premedicated with pargyline.2. The drug interaction was not antagonized when either reserpine or alpha-methyl-p-tyrosine were administered with pargyline. Neither reserpine nor alpha-methyl-p-tyrosine prevented the rise in brain stem 5-hydroxytryptamine content following monoamine oxidase inhibition, although the increase in catecholamines normally produced by pargyline was prevented.3. The development of fatal hyperthermia was completely prevented when rabbits were treated with p-chlorophenylalanine prior to pargyline premedication. In these animals, the concentration of brain stem catecholamines, but not 5-hydroxytryptamine, was increased.4. The results indicate that the hyperthermia evoked by pethidine or imipramine in combination with monoamine oxidase inhibitors can take place only in the presence of raised concentrations of 5-hydroxytryptamine in the brain stem.

Antihistamine-monoamine oxidase inhibitor interaction in rabbits

The ability of a drug to produce a fatal hyperpyrexia in rabbits pretreated with a monoamine oxidase inhibitor (MAOI) may be predictive of a serious clinical drug-drug interaction. These interactions appear to be due to 5-hydroxytryptamine (5-HT) potentiation. Since some antihistamines have been shown to block the neuronal 5-HT uptake, several antihistamines were tested in phenelzine-pretreated rabbits. The alkylamines (dexchlorpheniramine, chlorpheniramine, dexbrompheniramine, brompheniramine and pheniramine) and the ethylenediamines (mepyramine and tripelennamine) were active in producing a fatal hyperpyrexia in the MAOI-pretreated rabbits. Diphenhydramine and triprolidine produced a fatal hyperpyrexia in approximately one half of the animals tested. The mechanism responsible for the interaction between chlorpheniramine, a representative of the active compounds, and phenelzine appears to be 5-HT potentiation. Antihistamines that did not produce a fatal hyperpyrexia in the phenelzine pretreated rabbits were: phenyltoloxamine, promethazine, methdilazine, trimeprazine, meclizine, chlorcyclizine, cyproheptadine, phenindamine and dimethpyrindene. The potential use of the active compounds as antidepressants is also discussed.