In vivo pharmacodynamic studies of the disulfiram metabolite S-methyl N,N-diethylthiolcarbamate sulfoxide: inhibition of liver aldehyde dehydrogenase

Effects of disulfiram on choice behavior in a rodent gambling task: association with catecholamine levels

RATIONALE

Gambling disorder is a growing societal concern, as recognized by its recent classification as an addictive disorder in the DSM-5. Case reports have shown that disulfiram reduces gambling-related behavior in humans.

OBJECTIVES

The purpose of the present study was to determine whether disulfiram affects performance on a rat gambling task, a rodent version of the Iowa gambling task in humans, and whether any changes were associated with alterations in dopamine and/or norepinephrine levels.

METHODS

Rats were administered disulfiram prior to testing on the rat gambling task or prior to analysis of dopamine or norepinephrine levels in brain homogenates. Rats in the behavioral task were divided into two subgroups (optimal vs suboptimal) based on their baseline levels of performance in the rat gambling task. Rats in the optimal group chose the advantageous strategy more, and rats in the suboptimal group (a parallel to problem gambling) chose the disadvantageous strategy more. Rats were not divided into optimal or suboptimal groups prior to neurochemical analysis.

RESULTS

Disulfiram administered 2 h, but not 30 min, before the task dose-dependently improved choice behavior in the rats with an initial disadvantageous "gambling-like" strategy, while having no effect on the rats employing an advantageous strategy. The behavioral effects of disulfiram were associated with increased striatal dopamine and decreased striatal norepinephrine.

CONCLUSIONS

These findings suggest that combined actions on dopamine and norepinephrine may be a useful treatment for gambling disorders.

Elevation of Kynurenine Metabolites in Rat Liver and Serum: A Potential Additional Mechanism of the Alcohol Aversive and Anti-cancer Effects of Disulfiram?

Aims

The tryptophan metabolites 3-hydroxykynurenine (3-HK) and 3-hydroxyanthranilic acid (3-HAA) inhibit the liver mitochondrial low K_m aldehyde dehydrogenase and possess alcohol-aversive and immunosuppressant properties. As the disulfiram (DS) metabolite carbon disulphide activates enzymes forming 3-HK and 3-HAA, we investigated if repeated disulfiram treatment increases the hepatic and serum levels of these 2 metabolites.

Methods

Livers and sera of male Wistar rats were analysed for tryptophan and kynurenine metabolites after repeated DS treatment for 7 days.

Results

DS increased liver and serum [3-HK] and [3-HAA] possibly by increasing the flux of tryptophan down the hepatic kynurenine pathway and activation of kynurenine hydroxylase and kynureninase.

Conclusions

We provisionally suggest that elevation of some kynurenine metabolites may be an additional mechanism of the alcohol-aversive and anticancer effects of disulfiram.

Mode of action of S-methyl-N, N-diethylthiocarbamate sulfoxide (DETC-MeSO) as a novel therapy for stroke in a rat model

One approach for protecting neurons from excitotoxic damage in stroke is to attenuate receptor activity with specific antagonists. S-Methyl-N, N-diethylthiocarbamate sulfoxide (DETC-MeSO), the active metabolite of disulfiram, has been shown to be a partial antagonist of glutamate receptors and effective in reducing seizure. First, we investigated neuroprotective effect of DETC-MeSO on primary cortical neuronal culture under hypoxia/reoxygenation condition in vitro. Then, DETC-MeSO was administered subcutaneously for 4 and 8 days with the first injection occurring 1 h before or 24 h after reperfusion in the rat middle cerebral artery occlusion stroke model. Rats were subjected to the neuroscore test, and the brain was analyzed for infarct size. Monitoring neurotransmitter release was carried out by microdialysis. Heat shock proteins, key proteins involved in apoptosis and endoplasmic reticulum (ER) stress, were analyzed by immunoblotting. DETC-MeSO greatly reduced both cell death following hypoxia/reoxygenation and brain infarct size. It improved performance on the neuroscore test and attenuated proteolysis of αII-spectrin. The level of pro-apoptotic proteins declined, and anti-apoptotic and HSP27 protein expressions were markedly increased. Levels of the ER stress protein markers p-PERK, p-eIF2α, ATF4, JNK, XBP-1, GADD34, and CHOP significantly declined after DETC-MeSO administration. Microdialysis data showed that DETC-MeSO increased high potassium-induced striatal dopamine release indicating that more neurons were protected and survived under ischemic insult in the presence of DETC-MeSO. We also showed that DETC-MeSO can prevent gliosis. DETC-MeSO elicits neuroprotection through the preservation of ER resulting in reduction of apoptosis by increase of anti-apoptotic proteins and decrease of pro-apoptotic proteins.

A pilot study assessing the safety and latency-reversing activity of disulfiram in HIV-1-infected adults on antiretroviral therapy

BACKGROUND

Transcriptionally silent human immunodeficiency virus type 1 (HIV-1) DNA persists in resting memory CD4(+) T cells despite antiretroviral therapy. In a primary cell model, the antialcoholism drug disulfiram has been shown to induce HIV-1 transcription in latently infected resting memory CD4(+) T cells at concentrations achieved in vivo.

METHODS

We conducted a single-arm pilot study to evaluate whether 500 mg of disulfiram administered daily for 14 days to HIV-1-infected individuals on stable suppressive antiretroviral therapy would result in reversal of HIV-1 latency with a concomitant transient increase in residual viremia or depletion of the latent reservoir in resting memory CD4(+) T cells.

RESULTS

Disulfiram was safe and well tolerated. There was a high level of subject-to-subject variability in plasma disulfiram levels. The latent reservoir did not change significantly (1.16-fold change; 95% confidence interval [CI], .70- to 1.92-fold; P = .56). During disulfiram administration, residual viremia did not change significantly compared to baseline (1.53-fold; 95% CI, .88- to 2.69-fold; P = .13), although residual viremia was estimated to increase by 1.88-fold compared to baseline during the postdosing period (95% CI, 1.03- to 3.43-fold; P = .04). In a post hoc analysis, a rapid and transient increase in viremia was noted in a subset of individuals (n = 6) with immediate postdose sampling (HIV-1 RNA increase, 2.96-fold; 95% CI, 1.29- to 6.81-fold; P = .01).

CONCLUSIONS

Administration of disulfiram to patients on antiretroviral therapy does not reduce the size of the latent reservoir. A possible dose-related effect on residual viremia supports future studies assessing the impact of higher doses on HIV-1 production. Disulfiram affects relevant signaling pathways and can be safely administered, supporting future studies of this drug.

Disulfiram metabolite S-methyl-N,N-diethylthiocarbamate quantitation in human plasma with reverse phase ultra performance liquid chromatography and mass spectrometry

Disulfiram has been used extensively for alcohol abuse and may have a role in treatment for cocaine addiction. Recent data suggest that disulfiram may also reactivate latent HIV in reservoirs. Disulfiram has complex pharmacokinetics with rapid metabolism to active metabolites, including S-methyl-N,N-diethylthiocarbamate (DET-Me) which is formed from cytochrome P450 (CYP450). Assessing disulfiram in HIV-infected individuals with a CYP450 inducing drug (e.g., efavirenz) or a CYP450 inhibiting drug (e.g., HIV-1 protease inhibitors) requires an assay that can measure a metabolite that is formed directly via CYP450 oxidation. Therefore, an assay to measure concentrations of DET-Me in human plasma was validated. DET-Me and the internal standard, S-ethyldipropylthiocarbamate (EPTC) were separated by isocratic ultra performance liquid chromatography using a Waters Acquity HSS T3 column (2.1 mm × 100 mm, 1.8 μm) and detection via electrospray coupled to a triple quadrupole mass spectrometer. Multiple reaction monitoring in positive mode was used with DET-Me at 148/100 and the internal standard at 190/128 with a linear range of 0.500-50.0 ng/mL with a 5 min run time. Human plasma (500 μL) was extracted using a solid phase procedure. The interassay variation ranged from 1.86 to 7.74% while the intra assay variation ranged from 3.38 to 5.94% over three days. Representative results are provided from samples collected from subjects receiving daily doses of disulfiram 62.5mg or 250 mg.

Development of medications for alcohol use disorders: recent advances and ongoing challenges

During the past decade, efforts to develop medications for alcoholism have burgeoned. Three agents, disulfiram, naltrexone and acamprosate, are now approved in a large number of countries. Although many patients have benefited from existing medications, their effects are moderate, and some alcoholics fail to respond to them. A host of new agents are currently under active investigation. Critical barriers must be overcome to ensure that future efforts in the development of medications for alcohol use disorders reach full fruition. These challenges include: establishing key targets for drug discovery; validating animal and human screening models; and developing biomarkers to help predict treatment success. In addition, it is important to formulate methodological and statistical strategies to efficiently conduct alcohol pharmacotherapy trials; to specify genetic and phenotypic patient characteristics associated with efficacy and safety for lead compounds; to forge productive alliances among governmental agencies, the pharmaceutical industry and academic researchers to further drug development; and, ultimately and perhaps most difficult, to engage the practitioner community to incorporate medications into the alcohol treatment process.

Determination of in vivo adducts of disulfiram with mitochondrial aldehyde dehydrogenase

Extensive use for disulfiram (DSF) has been found in the aversion therapy treatment of recovering alcoholics. Although it is known to irreversibly inhibit hepatic aldehyde dehydrogenase (ALDH), the specific mechanism of in vivo inhibition of the enzyme by the drug has not been determined yet. We have demonstrated in this report a novel, but simple and rapid method for structurally characterizing in vivo derived protein-drug adducts by linking on-line sample processing to HPLC-electrospray ionization mass spectrometry (HPLC-MS) and HPLC-tandem mass spectrometry (HPLC-MS/MS). Employing this approach, rats were administered DSF, and their liver mitochondria were isolated and solubilized. Both native and in vivo DSF-treated mitochondrial ALDH (mALDH) were purified in one step with an affinity cartridge. The in vivo DSF-treated mALDH showed 77% inhibition in enzyme activity as compared with that of the control. Subsequently, the control and DSF-inhibited mALDH were both subjected to HPLC-MS analyses. We were able to detect two adducts on DSF-inhibited mALDH, as indicated by the mass increases of approximately 71 and approximately 100 Da. To unequivocally determine the site and structure of these adducts, on-line pepsin digestion-HPLC-MS and HPLC-MS/MS were performed. We observed two new peptides at MH(+) = 973.7 and MH(+) = 1001.8 in the pepsin digestion of DSF-inhibited enzyme. These two peptides were subsequently subjected to HPLC-MS/MS for sequence determination. Both peptides possessed the sequence FNQGQC(301)C(302)C(303), derived from the enzyme active site region, and were modified at Cys(302) by N-ethylcarbamoyl (+71 Da) and N-diethylcarbamoyl (+99 Da) adducts. These findings indicated that N-dealkylation may be an important step in DSF metabolism, and that the inhibition of ALDH occurred by carbamoylation caused by one of the DSF metabolites, most likely S-methyl-N,N-diethylthiocarbamoyl sulfoxide (MeDTC-SO). Finally, there was no evidence of the presence of an intramolecule disulfide bridge modification on the peptide FNQGQCCC.

Overview--in vitro inhibition of aldehyde dehydrogenase by disulfiram and metabolites

Disulfiram (DSF) has found extensive use in the aversion therapy treatment of recovering alcoholics. It is known that DSF or a metabolite irreversibly inhibits aldehyde dehydrogenase (ALDH). However, the actual mechanism of inhibition is still not known. In this work we describe the in vitro interactions of DSF, as well as a principal metabolite S-methyl-N,N-diethylthiocarbamoyl sulfoxide (MeDTC-SO), with both recombinant rat liver mitochondrial monomeric ALDH (rmALDH) and homotetrameric rmALDH. We show that DSF directly inhibits rmALDH (IC(50)=36.4 microM) by inducing the formation of an intramolecular disulfide bond. We also demonstrate by HPLC-MS analysis of a Glu-C digest of DSF-treated rmALDH that the intramolecular disulfide bridge formed involves two of the three cysteines located at the active site of the enzyme. Using a combination of HPLC-MS and HPLC-MS/MS, we further show that the electrophilic metabolite MeDTC-SO also inhibits rmALDH (IC(50)=4.62 microM). We isolate and identify a carbamoylated peptide at Cys(302) with the sequence FNQGQC(301)C(302)C(303). Hence we show that MeDTC-SO exhibits its inhibitory effect by covalently modifying the -SH side-chain of Cys(302), present at the active site rmALDH. Finally we show using SEC-MS that both DSF and MeDTC-SO do not prevent formation of the homotetramer of rmALDH, but inhibit the enzyme by acting directly at the active site of specific monomers of rmALDH.

Role of disulfiram in the in vitro inhibition of rat liver mitochondrial aldehyde dehydrogenase

The alcohol aversion therapy drug disulfiram has been shown to inhibit hepatic aldehyde dehydrogenase (ALDH), one of the key enzymes involved in ethanol metabolism. It is believed by some that disulfiram could be one of the active inhibitors in vivo. However, the actual interaction between disulfiram and ALDH remains ambiguous. We report here that when disulfiram inhibited recombinant rat liver mitochondrial ALDH (rlmALDH) in vitro, no significant molecular mass increase was detected during the first 30 min as determined by on-line HPLC-electrospray ionization mass spectrometry (LC-MS). This indicated that the inhibition in vitro was not caused directly by covalent adduct formation on the enzyme. We subsequently subjected both control and disulfiram-inhibited rlmALDH to Glu-C proteolytic digestion. LC-MS analysis of the Glu-C digestion of disulfiram-inhibited enzyme revealed that one peptide of M(r) = 4821, which contained the putative active site of the enzyme, exhibited a mass decrease of 2 amu as compared with the same peptide found in the Glu-C digestion of the control (M(r) = 4823). We believe that the loss of 2 amu indicated that inhibition of rlmALDH in vitro was due to formation of an intramolecular disulfide bond between two of the three adjacent cysteines in the active site, possibly via a very rapid and unstable mixed disulfide interchange reaction. Further confirmation of the intramolecular disulfide bond formation came from the fact that by adding dithiothreitol (DTT) we were able to recover partial enzyme activity. In addition, the peptide of M(r) = 4821 observed in the Glu-C digestion of the disulfiram-treated ALDH reverted to M(r) = 4823 after treatment with DTT, which indicated that the disulfide bond was reduced. We, thereby, conclude that disulfiram inhibited rlmALDH by forming an intramolecular disulfide, possibly via a fast intermolecular disulfiram interchange reaction.

Identification of the protein-drug adduct formed between aldehyde dehydrogenase and S-methyl-N,N-diethylthiocarbamoyl sulfoxide by on-line proteolytic digestion high performance liquid chromatography electrospray ionization mass spectrometry

Disulfiram has been used clinically as an aversion therapy treatment for recovering alcoholics. One of its metabolites, S-methyl-N, N-diethylthiocarbamoyl sulfoxide (MeDTC-SO), is currently believed by some to be the active metabolite in vivo. We demonstrate in this report that MeDTC-SO is a potent irreversible inhibitor of recombinant rat liver mitochondrial aldehyde dehydrogenase (rlmALDH), the enzyme responsible for oxidizing acetaldehyde formed during ethanol metabolism. Recombinant rlmALDH was inhibited by MeDTC-SO after in vitro incubation with an IC(50) = 4.62 microM. The inhibition of rlmALDH was found to be accompanied by a concomitant increase of approximately 100 Da to the molecular mass of the native enzyme as determined by on-line high performance liquid chromatography (HPLC) electrospray ionization mass spectrometry (LC/MS), indicating that a covalent modification has occurred. To determine the site and structure of this covalent adduct, we developed a novel approach to characterize specific protein-drug interactions by linking a proteolytic enzyme digestion cartridge on-line with LC/MS. The on-line pepsin digestion LC/MS of MeDTC-SO-inhibited rlmALDH revealed an ion at MH(2)(2+) = 500.9, which was not present in the pepsin digestion of the non-inhibited enzyme. This peptide was tentatively attributed to the putative active site peptide (FNQGQC(301)C(302)C(303)) plus the adduct. This peptide was subjected to analysis by LC/MS/MS, which allowed us to determine that the covalent modification was associated with a single carbamoyl adduct at Cys-302, which has been shown to be the active site nucleophile of the enzyme.

Glutathione carbamoylation with S-methyl N,N-diethylthiolcarbamate sulfoxide and sulfone. Mitochondrial low Km aldehyde dehydrogenase inhibition and implications for its alcohol-deterrent action

S-Methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) and sulfone (DETC-MeSO2) both inhibit rat liver low Km aldehyde dehydrogenase (ALDH2) in vitro and in vivo (Nagendra et al., Biochem Pharmacol 47: 1465-1467, 1994). DETC-MeSO has been shown to be a metabolite of disulfiram, but DETC-MeSO2 has not. Studies were carried out to further investigate the inhibition of ALDH2 by DETC-MeSO and DETC-MeSO2. In an in vitro system containing hydrogen peroxide and horseradish peroxidase, the rate of DETC-MeSO oxidation corresponded to the rate of DETC-MeSO2 formation. Carbamoylation of GSH by both DETC-MeSO and DETC-MeSO2 was observed in a rat liver S9 fraction. Carbamoylation of GSH was not observed in the presence of N-methylmaleimide. In in vitro studies, DETC-MeSO and DETC-MeSO2 were equipotent ALDH2 inhibitors when solubilized mitochondria were used, but DETC-MeSO was approximately four times more potent than DETC-MeSO2 in intact mitochondria. In studies with rats, the dose (i.p. or oral) required to inhibit 50% ALDH2 (ED50) was 3.5 mg/kg for DETC-MeSO and approximately 35 mg/kg for DETC-MeSO2, approximately a 10-fold difference. Furthermore, maximum ALDH2 inhibition occurred 1 hr after DET(-MeSO administration, whereas maximal ALDH2 inhibition occurred 8 hr after DETC-MeSO2 dosing. DETC-MeSO is, therefore, not only a more potent ALDH2 inhibitor than DETC-MeSO2 in vivo, but also in vitro when intact mitochondria are utilized. The in vitro results thus support the in vivo findings. Since oxidation of DETC-MeSO can occur both enzymatically and non-enzymatically, it is possible that DETC-MeSO2 is formed in vivo. DETC-MeSO2, however, is not as effective as DETC-MeSO in inhibiting ALDH2, probably because it has difficulty penetrating the mitochondrial membrane. Thus, even if DETC-MeSO2 is formed in vivo from DETC-MeSO, it is the metabolite DETC-MeSO that is most likely responsible for the inhibition of ALDH2 after disulfiram administration.

Pharmacotherapies for alcohol problems: a review of research with focus on developments since 1991

Research on medications to treat alcohol problems has flourished in the last 5 years. Whereas before this time most projects focused on withdrawal agents, at least equal interest has now extended to drugs that may directly reduce urge to drink. The most promising medications in this regard are the opiate antagonists and acamprosate. Considerable attention has also been devoted to serotonergic agents. As aids to detoxification, pharmacologic agents that affect the multiple neural systems disrupted by acute alcohol withdrawal remain under active investigation. Significant progress is also being made in identifying medications to assist alcoholics suffering collateral psychopathology, especially depression and anxiety based disorders. Unfortunately, fewer gains have been realized in the development of medications to assist patients simultaneously dependent on both alcohol and illicit drugs. Also, research to develop amethystic agents remains in its very early stages.

S-methyl N,N-diethylthiocarbamate sulfone, a potential metabolite of disulfiram and potent inhibitor of low Km mitochondrial aldehyde dehydrogenase

Disulfiram inhibits hepatic aldehyde dehydrogenase (ALDH) causing an accumulation of acetaldehyde after ethanol ingestion. It is thought that disulfiram is too short-lived in vivo to directly inhibit ALDH, but instead is biotransformed to reactive metabolites that inhibit the enzyme. S-Methyl N,N-diethylthiocarbamate (MeDTC) sulfoxide has been identified in the blood of animals given disulfiram and is a potent inhibitor of ALDH (Hart and Faiman, Biochem Pharmacol 46: 2285-2290, 1993). MeDTC sulfone is a logical metabolite of MeDTC sulfoxide. Therefore, we investigated the effects of MeDTC sulfone on the activity of rat hepatic low Km mitochondrial ALDH, the major enzyme in the metabolism of acetaldehyde. MeDTC sulfone inhibited the low Km mitochondrial ALDH in vitro with an IC50 of 0.42 +/- 0.04 microM (mean +/- SD, N = 5) compared with disulfiram, which had an IC50 of 7.5 +/- 1.2 microM under the same conditions. The inhibition of ALDH by MeDTC sulfone was time dependent. The decline in ALDH activity followed pseudo first-order kinetics with an apparent half-life of 2.1 min at 0.6 microM MeDTC sulfone. Inhibition of ALDH by MeDTC sulfone was apparently irreversible; dilution of the inhibited enzyme did not restore lost activity. The substrate (acetaldehyde, 80 microM) and cofactor (NAD, 0.5 mM) together completely protected ALDH from inhibition by MeDTC sulfone; substrate alone partially protected the enzyme. Addition of either thiol-containing compound glutathione (GSH) or dithiothreitol (DTT) to MeDTC sulfone before incubation with the enzyme increased the IC50 of MeDTC sulfone by 7- to 14-fold. Neither GSH nor DTT could restore lost ALDH activity after exposure of the enzyme to MeDTC sulfone. Results of these studies indicate that MeDTC sulfone, a potential metabolite of disulfiram, is a potent, irreversible inhibitor of low Km mitochondrial ALDH.

Inhibition of rat liver low Km aldehyde dehydrogenase by thiocarbamate herbicides. Occupational implications

S-Methyl N,N-diethylthiolcarbamate (DETC-Me) is a metabolite formed during the bioactivation of disulfiram. The formation of its corresponding sulfoxide, S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO), from DETC-Me is required for low Km mitochondrial aldehyde dehydrogenase (ALDH2, EC 1.2.1.3) inhibition. DETC-Me is similar in structure to thiocarbamate herbicides with the general structure R1R2NC(O)SR3. Representative herbicides studied were n-propyl, n-propylthiocarbamate ethyl ester (EPTC), molinate, vernolate, ethiolate and butylate. All of these thiocarbamate herbicides inhibited rat liver ALDH2 in vivo. The dose of these thiocarbamates that inhibited rat liver ALDH2 by 50% (ID50) when administered 8 hr before determination of ALDH2, was found to be 5.2, 3.1, 1.6, 12, and 174 mg/kg, respectively. These thiocarbamates were ineffective rat liver ALDH2 inhibitors in vitro, unless rat liver microsomes and an NADPH-generating system were added to the incubation. The respective thiocarbamate sulfoxides were formed when the thiocarbamates were incubated with liver microsomes and an NADPH-generating system. The thiocarbamate sulfoxides all inhibited rat liver ALDH2 in vitro. An equimolar dose of molinate and molinate sulfoxide inhibited rat liver ALDH2 in vivo to the same degree. Molinate-treated rats challenged with ethanol exhibited a disulfiram-like ethanol reaction. In conclusion, thiocarbamate herbicides inhibit ALDH2, probably due to the formation of their sulfoxide, and therefore have the potential to produce a disulfiram-like ethanol reaction in an unsuspecting population.

Diethyldithiocarbamate methyl ester sulfoxide, an inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase and putative metabolite of disulfiram

S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) is a potent inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase (ALDH2) both in vivo and in vitro, and has been proposed to be the metabolite responsible for ALDH2 inhibition by disulfiram. Diethyldithiocarbamate methyl ester (DDTC-Me), a key intermediate in the metabolism of disulfiram, has been shown to be bioactivated by microsomal monooxygenases to diethyldithiocarbamate methyl ester sulfoxide (DDTC-Me sulfoxide). Studies were conducted to determine if DDTC-Me sulfoxide was also an active metabolite of disulfiram and inhibitor of ALDH2. DDTC-Me sulfoxide inhibited ALDH2 in vitro with an IC50 of 10 microM, and in vivo with an ID50 of 31 mg/kg (170 mumol/kg). Maximal ALDH2 inhibition in vivo was observed 8 hr after the administration of 45.2 mg/kg DDTC-Me sulfoxide, with ALDH2 activity returning to control levels after 48 hr. Although DDTC-Me sulfoxide inhibited ALDH2 in vivo, DDTC-Me sulfoxide was not detected in plasma from rats treated with either disulfiram (75 mg/kg), DDTC-Me (122.25 mg/kg), or DDTC-Me sulfoxide (45.2 mg/kg). However, DDTC-Me and S-methyl N,N-diethylthiolcarbamate (DETC-Me) were detected in plasma from rats treated with DDTC-Me sulfoxide. In rats treated with DDTC-Me sulfoxide and challenged with ethanol, a small increase of approximately microM in blood acetaldhyde and an inconsistent drop in blood pressure was observed. In conclusion, DDTC-Me sulfoxide inhibited ALDH2 in vitro and in vivo, was less potent than DETC- MeSO, and was not detected after disulfiram administration.