Acute toxicity of propoxyphene salts

Dopamine and dobutamine reduce myocardial d-propoxyphene content in experimentally intoxicated rats

The effect of sympathomimetic intervention with dopamine or dobutamine on the myocardial uptake of d-propoxyphene was investigated experimentally in rats. The d-propoxyphene (19 mg kg-1 h-1) was continuously infused, intravenously, over 45 min. After 20 min of infusion the rats were given either dopamine (12.5 micrograms kg-1 min-1 or 25 micrograms kg-1 min-1), dobutamine (25 micrograms kg-1 min-1 or 45 micrograms kg-1 min-1) or normal saline (control). Each group consisted of eight rats. The myocardial d-propoxyphene content was significantly lower in the two groups given dopamine and in the group given dobutamine 45 micrograms kg-1 min-1 than in the control group (P less than 0.05). This finding indicates the benefit of early sympathomimetic intervention with either dopamine or dobutamine in d-propoxyphene intoxication.

Circulatory shock following intravenous propoxyphene poisoning. An experimental study of cardiac function and metabolism in pentobarbital-anesthetized pigs

The effects of continuously administered intravenous propoxyphene chloride (15 mg X min-1) on ECG, systemic, pulmonary and coronary circulations and myocardial oxygenation were investigated in eight pentobarbital-anesthetized pigs. Circulatory shock, defined as a systolic blood pressure below 60 mmHg (8.0 kPa) and a cardiac output of approximately 2.0 l X min-1 X m-2, occurred after 675 to 2025 mg propoxyphene chloride. At the time when shock occurred plasma concentrations of propoxyphene ranged from 9.6 to 15.3 micrograms X ml-1 which is within the range of the lethal concentration observed in man. Statistically significant decreases were observed for the following variables: maximum rate of rise of left ventricular pressure dP/dt (-90%), mean arterial pressure (-73%), heart rate (-46%), cardiac index (-58%), stroke volume index (-22%), left ventricular stroke work index (-85%), right ventricular stroke work index (-63%) and systemic vascular resistance (-50%). Mean pulmonary arteriolar occlusion pressure increased (+42%), whereas mean right atrial pressure and pulmonary vascular resistance remained unchanged. The arteriovenous oxygen difference increased (+53%) and total body oxygen consumption decreased (-35%). The following coronary variables decreased: coronary sinus blood flow (-57%), coronary vascular resistance (-65%), myocardial oxygen consumption (-68%), myocardial oxygen extraction (-26%) and myocardial lactate extraction (-28%). Prolongation of the ECG PQ and QRS intervals were recorded shortly before shock appeared, and all animals were in sinus rhythm till the last minute before death. The results indicate that intravenously administered propoxyphene besides being a powerful negative inotropic and chronotropic agent, is also a potent systemic and coronary vasodilator.

Lack of evidence of increased lethality due to propoxyphene overdose in the presence of ethanol in male Wistar rats

The primary purpose of the present investigation was to evaluate if the presence of ethanol increased lethality induced by propoxyphene. A secondary aim was to study the effect of naloxone on propoxyphene lethality alone, and on the concomitant administration of propoxyphene and ethanol. Male Wistar rats (210-330 g) were used as test animals. Propoxyphene (175 mg/kg) and ethanol (2 g/kg) were administered by gastric intubation, naloxone (2 mg/kg) by subcutaneous injection. Four groups, each consisting of 19 rats, received either of the following drug treatments: Propoxyphene, ethanol + propoxyphene, naloxone + propoxyphene, and naloxone + ethanol + propoxyphene respectively. The drugs were given in the sequence mentioned at the beginning of the experiment. Naloxone was also given 45 and 90 min later. Mortality was reduced to 42% in the group that received ethanol and propoxyphene compared to 73% in the group that received propoxyphene only. Naloxone protected against lethality in both groups. Some animals died despite naloxone administration, possibly due to a nonopioid cardiotoxic effect of propoxyphene or its metabolite. An increase in the propoxyphene/norpropoxyphene (P/N) ratio due to an increase in the absolute concentrations of propoxyphene and a decrease in the absolute levels of norpropoxyphene in blood, brain, and heart tissues was observed in the ethanol + propoxyphene group, compared to the propoxyphene group. In the animals which died, the highest P/N ratio was observed in brain tissue and the lowest in heart muscle. Despite the pharmacokinetic data obtained in this investigation indicating impaired propoxyphene metabolism in the presence of ethanol, ethanol did not enhance propoxyphene-induced lethality.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased absorption of propoxyphene by activated charcoal

In 1968 we first suggested that activated charcoal (AC) should be administered in the emergency treatment of propoxyphene overdosage. The dramatic increase in recent years of deaths involving propoxyphene has prompted us to again evaluate the efficacy of AC in preventing absorption of propoxyphene from the GI tract. Male rats (100-125 g) were administered propoxyphene hydrochloride (P-HCl, 350 mg/kg) or propoxyphene napsylate (P-N, 825 mg/kg) either dissolved or suspended in 5% acacia in H2O. After 30 min the rats were administered either AC at 10 times the drug dose or water. Surviving rats were sacrificed at 1, 2, 4, 8, 12, and 24 h; the brain, liver, and both kidneys were removed intact, weighed, and stored at -70 degrees C. After lyophilization, the tissues were analyzed for propoxyphene and its metabolite, norpropoxyphene, by GLC. There were significantly less deaths in rats that received P-HCl + AC or P-N + AC than rats that received either P-HCl or P-N alone (9 vs 19, p less than .01 and 5 vs 10, p less than .05 respectively). Tissue levels of propoxyphene and norpropoxyphene were similarly significantly reduced. These studies provide further evidence of the efficacy of AC in propoxyphene overdosage.

d-Propoxyphene acts differently from morphine on opioid receptor-effector mechanisms

The actions of d-propoxyphene and morphine on opioid receptor mechanisms were compared. In assay measuring receptor binding selectivity in vitro, with dihydromorphine, naloxone and an enkephalin analogue as radioactive ligands, d-propoxyphene differed from morphine in having a higher relative affinity for sites occupied by the peptide. Naloxone was more potent in antagonizing morphine- than d-propoxyphene-induced antinociception in the mouse hot-plate test. In morphine-tolerant mice showing three-fold lower morphine sensitivity the antinociceptive efficacy of d-propoxyphene was unchanged. The results indicate differences in receptor-effector mechanisms between d-propoxyphene and morphine.