Determination of l-alpha-acetylmethadol (LAAM), norLAAM, and dinorLAAM in clinical and in vitro samples using liquid chromatography with electrospray ionization and tandem mass spectrometry.

l-Alpha-acetylmethadol (LAAM) is an alternative to methadone for the maintenance treatment of opioid dependence. LAAM has a longer therapeutic half-life than methadone, primarily because it is metabolized to more active metabolites, norLAAM and dinorLAAM. We have developed a liquid chromatography-tandem mass spectrometry method capable of measuring LAAM and its metabolites, norLAAM and dinorLAAM, at lower concentrations with 1.0-mL aliquots of plasma (range of 0.25 to 100 ng/mL) or higher concentration with 0.2-mL aliquots of plasma (range 1.25 to 500 ng/mL). It has acceptable precision and accuracy across both linear ranges, as well as in the urine matrix. Results from this assay correlate well with our previously validated gas chromatograghy-mass spectrometry method. All analytes had acceptable stability after three freeze-thaw cycles, room temperature storage for 20 h, or storage of extracts either at -20 degrees C for 6 days or on the autosampler (10 degrees C) for 4 days. The pharmacokinetics of LAAM, norLAAM, and dinorLAAM were determined for the first time in three male opioid-naive individuals receiving a single oral dose of 5 mg LAAM/70 kg. Using this method, we could monitor the in vitro N-demethylation of LAAM and norLAAM at substrate concentrations in the therapeutic range of 0.5 and 1.0 microM by cDNA-expressed cytochrome P450s. This confirmed the involvement of cytochrome P450s 3A4, 2B6, 2C8, and 2C18 at therapeutic concentrations of LAAM. An accurate and precise method for determination of LAAM and its metabolites, norLAAM and dinorLAAM, that is suitable for both in vivo and in vitro metabolism studies has been developed and validated.

Heroin discriminative stimulus effects of methadone, LAAM and other isomers of acetylmethadol in rats.

RATIONALE: LAAM (alpha- l-acetylmethadol) is a derivative of the synthetic mu-opiate agonist methadone and is one of the four isomers of acetylmethadol. Methadone and LAAM have similar pharmacological properties and both are approved medications for the treatment of heroin dependency disorders. Few studies have reported on the pharmacology of acetylmethadol's other isomers and most of these have focused on their potential analgesic activity. OBJECTIVES: The purpose of the present investigation was to examine the discriminative stimulus effects of LAAM, the other isomers of acetylmethadol, and methadone in rats trained to discriminate heroin from water, and to compare the duration of the discriminative stimulus effects of heroin, methadone, and LAAM. METHODS: Long-Evans rats were trained to discriminate 0.3 mg/kg heroin from water under a fixed ratio 10 (FR10) schedule of food reinforcement. Dose-response functions for heroin, methadone, LAAM, three other isomers of acetylmethadol: alpha- d-acetylmethadol, beta- d-acetylmethadol, beta- l-acetylmethadol, and its precursor, beta- l-methadol were examined. Additionally, the time course effects for heroin, methadone, and LAAM were examined. RESULTS: LAAM and methadone dose-dependently occasioned heroin-like discriminative stimulus effects. Two of acetylmethadol's isomers, alpha- d-acetylmethadol and beta- d-acetylmethadol, were more potent than LAAM in producing heroin-like effects. The beta- l-methadol precursor and beta- l-acetylmethadol did not fully substitute for heroin's discriminative stimulus. LAAM elicited heroin-like discriminative stimulus effects for at least 6 h and generated partial generalization up to 36 h following administration. CONCLUSIONS: Methadone, LAAM, beta- d-acetylmethadol and alpha- d-acetylmethadol, but not beta- l-acetylmethadol and beta- l-methadol evoke heroin-like discriminative stimulus effects.

Absolute configuration of (-)-alpha-acetylmethadol hydrochloride.

beta-[2-(Dimethylamino)propyl]-alpha-ethyl-beta-phenylbenzeneethanol+ ++ acetate ester hydrochloride, C23H32NO2+. Cl-.H2O, M(r) = 407.9, monoclinic, P2(1), a = 15.608 (4), b = 8.637 (2), c = 17.273 (5) A, beta = 97.71 (2) degrees, V = 2307.4 (1) A3, Z = 4 (two methadol hydrochlorides and two water molecules per asymmetric unit), Dx = 1.17 Mg m-3, lambda (Cu K alpha) = 1.54184 A, mu = 1.64 mm-1, F(000) = 880, T = 295 K, final R = 0.069, wR = 0.064 for 2559 independent observed reflections. Both asymmetric C atoms in the two independent methadol molecules are 'S'. Of the two N-H moieties one acts as a hydrogen-bond donor to a Cl atom (N-H = 1.21, H...Cl = 1.85, N...Cl = 3.03 A, N-H...Cl = 162.3 degrees) and the other is a donor to a water molecule (N-H = 0.90, H...O = 2.06, N...O = 2.80 A, N-H...O = 138.2 degrees). In addition, both water molecules hydrogen bond to both Cl atoms with O...Cl distances in the range 3.06-3.36 A. A comparison of torsion angles for the two independent methadol molecules indicates that there is very little stereochemical similarity between them.