Pharmacokinetic interactions between ethanol and heroin: a study on post-mortem cases.

INTRODUCTION: Ethanol and heroin are both depressant drugs on the central nervous system, and combined use is known to be dangerous due to pharmacodynamic interactions, leading to an even higher risk of respiratory depression and death. In addition, previous studies have suggested a pharmacokinetic interaction between ethanol and the metabolism of heroin. The aim of the present study was to investigate if there was a pharmacokinetic interaction between heroin and ethanol, by comparing concentrations of heroin metabolites in cases with and without ethanol, as detected in blood samples collected from a large material of forensic autopsy cases. METHODS: The material consisted of 1583 forensic autopsy cases, all containing 6-monoacetylmorphine (6-MAM), as evidence of heroin intake, in either blood or urine samples, from the time period between the 1st of January 2000 and the 31st of December 2012. Due to the high risk of post-mortem ethanol formation in cases revealing blood ethanol concentrations between 0.1 and 0.3‰, these cases were excluded from the study, along with cases where the analysis for ethanol was missing. After this exclusion of cases, the material (n=1474) was divided into two groups; one group where ethanol was not detected in blood (n=1160), and another group where ethanol was detected in blood at or above the concentration of 0.4‰ (n=314). Furthermore, the material was also divided into two other subgroups; one group where 6-MAM was detected in blood samples, indicating a very recent intake of heroin, and another group where 6-MAM was detected in the urine, but not in blood, indicating a less recent heroin intake. RESULTS: The concentration ratios of morphine/6-MAM, morphine-3-glucuronide (M3G)/morphine, and morphine-6-glucuronide (M6G)/morphine in blood samples, were all significantly lower in the ethanol positive cases compared with that of the ethanol negative cases. For the subgroup of cases revealing a very recent intake of heroin (n=645), only the morphine/6-MAM ratio was significantly lower in the ethanol positive cases than in the ethanol negative cases. For the subgroup of cases with a less recent heroin intake (n=817), lower M3G/morphine and M6G/morphine ratios were found among the ethanol positive cases. CONCLUSIONS: The results indicate that ethanol inhibits two steps in the heroin metabolism; the hydrolysis of 6-MAM to morphine, and the glucuronidation of morphine to M3G and M6G. This pharmacokinetic interaction could further complicate the outcome after combined use of heroin and ethanol, in addition to the already well-known pharmacodynamic interactions.

Levels of heroin and its metabolites in blood and brain extracellular fluid after i.v. heroin administration to freely moving rats.

BACKGROUND AND PURPOSE: Heroin, with low affinity for µ-opioid receptors, has been considered to act as a prodrug. In order to study the pharmacokinetics of heroin and its active metabolites after i.v. administration, we gave a bolus injection of heroin to rats and measured the concentration of heroin and its metabolites in blood and brain extracellular fluid (ECF). EXPERIMENTAL APPROACH: After an i.v. bolus injection of heroin to freely moving Sprague-Dawley rats, the concentrations of heroin and metabolites in blood samples from the vena jugularis and in microdialysis samples from striatal brain ECF were measured by ultraperformance LC-MS/MS. KEY RESULTS: Heroin levels decreased very fast, both in blood and brain ECF, and could not be detected after 18 and 10 min respectively. 6-Monoacetylmorphine (6-MAM) increased very rapidly, reaching its maximal concentrations after 2.0 and 4.3 min, respectively, and falling thereafter. Morphine increased very slowly, reaching its maximal levels, which were six times lower than the highest 6-MAM concentrations, after 12.6 and 21.3 min, with a very slow decline during the rest of the experiment and only surpassing 6-MAM levels at least 30 min after injection. CONCLUSIONS AND IMPLICATIONS: After an i.v. heroin injection, 6-MAM was the predominant opioid present shortly after injection and during the first 30 min, not only in the blood but also in rat brain ECF. 6-MAM might therefore mediate most of the effects observed shortly after heroin intake, and this finding questions the general assumption that morphine is the main and most important metabolite of heroin.

Simultaneous measurement of heroin and its metabolites in brain extracellular fluid by microdialysis and ultra performance liquid chromatography tandem mass spectrometry.

INTRODUCTION: The pharmacokinetic profile and systemic bioavailability of a substance is often described by blood or total tissue concentrations. For centrally acting drugs, like opioids, the free fraction of active compound in brain extracellular fluid (ECF) is more likely to be correlated to the pharmacodynamic effects than the blood concentrations. Drugs of abuse, like heroin, are often administered intravenously as bolus injections, and the blood concentrations might change rapidly due to metabolism and distribution. The aim of our study was to establish a method to measure the free fraction of heroin and its metabolites in brain ECF, and follow their fast changes in concentration. METHODS: Sprague-Dawley rats were injected intravenously with a bolus of heroin. Heroin and its main metabolites 6-monoacetylmorphine, morphine and morphine-3-glucuronide were measured simultaneously. Brain microdialysis was used for sampling and a method for quantification using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed. Deuterated analogues for each analyte were included in the microdialysis perfusion solution as calibrators for recovery estimation. RESULTS: A highly sensitive UPLC-MS/MS method allowed short sampling intervals, down to one minute, and the simultaneous detection of each analyte and its specific deuterated analogues, making possible the individual recovery calculation for each compound of interest. This method allowed us to determine the pharmacokinetic profiles of heroin and its metabolites in brain-ECF in the same animal after an intravenous injection of heroin. DISCUSSION: Our method makes detecting concurrently the rapid changes in concentrations of heroin and its metabolites in brain ECF possible, despite the rapid metabolism of heroin. Recovery was measured specifically for each analyte in the same sample by carefully combining different deuterated analogues. This technique can be applied to pharmacokinetic studies where more than one compound of interest has to be monitored, and to study distribution of prodrugs or drugs with active metabolites.