Plasma levels and symptom complaints in patients maintained on daily dosage of methadone hydrochloride

Plasma methadone levels, symptom complaints, and urine tests for illicit opiate use were followed weekly in 17 patients on a methadone maintenance program. There were very large differences between patients in the plasma level established at a given dosage, implying large differences in the rate of methadone metabolism. Despite virtually constant daily dosage, the plasma methadone levels fluctuated greatly from week to week and from day to day in individual patients. With rate exceptions there was no relationship between plasma methadone level and symptom complaints or between weekly chamges in plasma methadone level and changes in symptom complaints. Except possible to identify the ocassional patient with unusually low plasam methadone levels, the determination of methadone levels is not likely to be or practical value in methadone programs.

Failure of the opiate antagonist naloxone to modify hypnotic analgesia

Hypnotic analgesia in some respects resembles opiate analgesia. We tested the hypothesis that some features of hypnotic analgesia are mediated through neuronal pathways activating specific opiate receptors in brain. The opiate antagonist naloxone had no effect on hypnotic analgesia in three subjects. Thus, the hypothesis was not confirmed.

Partial purification of an opiate receptor from mouse brain

A proteolipid isolated from a lipid extract of mouse brain demonstrates stereospecific binding properties for levorphanol. It is present only in neuronal tissue and most abundant in the rhombencephalon. One component saturates at a concentration corresponding to maximum pharmacologic effect in vivo. The estimated mass is 60,000 daltons per bound opiate molecule.

Lethality of the morphinan isomers levorphanol and dextrorphan

Significantly different (P<0.05) LD(50) values were found in Swiss-Webster mice for levorphanol (73 mg/kg, i.p.) and dextrorphan (120 mg/kg, i.p.). A subcutaneous injection of naloxone 15 min before challenge prevented the lethal effect of an LD(98) of levorphanol, with ED(50) value of 1.36 mg/kg. Naloxone, in doses from 2 to 100 mg/kg, did not prevent death caused by 150 mg/kg of either dextrorphan or levorphanol. Levorphanol was lethal for mice pretreated with 10 mg/kg of naloxone, a dose sufficient to block opiate-specific lethal effects, but the LD(50) value was 109 mg/kg, in contrast to 73 mg/kg in the absence of naloxone. By the criteria of stereospecificity and naloxone blockade, levorphanol-induced mortality in mice is a typical opiate effect in the lower of the two dose ranges studied. At higher doses of levorphanol a non-specific effect supervenes, with an LD(50) value virtually the same as that of dextrorphan.

Morphine-tolerant longitudinal muscle strip from guinea-pig ileum

1. Implantation of morphine pellets in guinea-pigs produced a high degree of tolerance and dependence within 3 days.2. The contractions of the longitudinal muscle induced by electrical stimulation of the myenteric plexus-longitudinal muscle preparations obtained from tolerant animals were less depressed by morphine than the contractions evoked in preparations from non-tolerant animals.3. Naloxone did not alter the size of the evoked twitch but antagonized the depressant action of morphine in tolerant and in non-tolerant animals. When given to tolerant guinea-pigs, naloxone caused an increase in intestinal activity in vivo.4. The contractile response of the longitudinal muscle to acetylcholine was the same in preparations obtained from tolerant and non-tolerant animals. Electrically evoked contractions of the myenteric plexus-longitudinal muscle preparations from tolerant animals showed reduced sensitivity to the depressant effects of adrenaline, isoprenaline, and particularly, dopamine.

Cellular and metabolic tolerance to an opioid narcotic in mouse brain

1. Running activity and brain levorphanol concentration were measured in nontolerant and tolerant mice given various doses of (3)H-levorphanol.2. The principal factor responsible for tolerance in the mouse is a loss of sensitivity to the narcotic drug at the cellular level in brain; despite adequate brain concentrations, the pharmacological effects are diminished or absent.3. There is also metabolic tolerance; a given dose establishes a lower brain concentration in tolerant than in non-tolerant animals.4. The two kinds of tolerance are distinguished here and the contribution of each is assessed.

Stereospecific and nonspecific interactions of the morphine congener levorphanol in subcellular fractions of mouse brain

A METHOD IS DESCRIBED FOR ANALYZING THE ASSOCIATION OF THE OPIATE NARCOTIC LEVORPHANOL WITH BRAIN TISSUE INTO THREE COMPONENTS: nonsaturable, saturable nonspecific, and saturable stereospecific. The method may be of general applicability for the study of the interaction of drugs with body tissues. In mouse brain the stereospecific binding of levorphanol represents only 2% of the total association of drug with tissue, and it was found only in certain membrane fractions. The material responsible for the stereospecific binding might be the opiate receptor.

Alcohol dependence and opiate dependence: lack of relationship in mice

According to a recently proposed hypothesis, physical dependence upon alcohol is due to the formation of an endogenous opiate. We tested the hypothesis by determining whether or not ethanol-dependent mice would show typical opiate-dependent behavior (withdrawal jumping syndrome) when challenged with the opiate antagonist naloxone. Our results do not support the hypothesis.

Narcotic tolerance and dependence: lack of relationship with serotonin turnover in the brain

Serotonin turnover was measured in mouse brain by means of the conversion of radioactivity from labeled tryptophan into serotonin. Animals with a high degree of tolerance to and physical dependence on morphine did not differ from control mice.

Tolerance to opioid narcotics, II. Cellular tolerance to levorphanol in mouse brain

Mice were made tolerant to a large dose of levorphanol, a congener of morphine. Then (3)H-levorphanol was given. The concentration of free, unchanged levorphanol in the brain water (ultrafiltrate) was found to be much higher than required to produce pharmacologic effects in nontolerant animals. The result indicates that tolerance arises from a diminished sensitivity to the drug at cellular or subcellular sites of drug action in the brain.