Raka Jain

Evidence for the Involvement of Dopamine Transporters in Behavioral Stimulant Effects of Modafinil

Modafinil is prescribed for numerous medical conditions, but the drugs mechanism of action is unclear. Here, we examined the interaction of modafinil with receptors and transporters in vitro and compared pharmacological effects of the drug with those produced by indirect dopamine (DA) agonists 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (GBR12909) and (+)-methamphetamine (METH). Modafinil was screened at various receptors and transporters using binding assays. Transporter-mediated uptake and release were examined in rat brain synaptosomes. Effects of modafinil on motor activity and neurochemistry were determined in rats undergoing in vivo microdialysis in nucleus accumbens. Of the receptors and transporters assayed, modafinil displayed measurable potency only at DA transporters (DAT), inhibiting [3H]DA uptake, with an IC50 value of 4.0 μM. Accordingly, modafinil pretreatment (10 μM) antagonized METH-induced release of the DAT substrate [3H]1-methyl-4-phenylpyridinium. Intravenous modafinil (20 and 60 mg/kg) produced dose-dependent increases in motor activity and extracellular DA, without affecting serotonin (5-HT). Analogous results were observed for GBR12909 (1 and 3 mg/kg), whereas METH (0.3 and 1 mg/kg) increased DA and 5-HT. Locomotor effects of all drugs were positively correlated with dialysate DA (P < 0.001). Interestingly, modafinil pretreatment reduced METH-induced ambulation and DA release. Our data show that modafinil interacts with DAT sites in rat brain, a property shared with agonist medications under investigation for treating cocaine dependence. Nondopaminergic mechanisms may also contribute to the pharmacology of modafinil. Finally, the results suggest that modafinil should be tested as an adjunct for treating METH addiction.

Influence of sweet tasting solutions on opioid withdrawal

The effect of the ingestion of palatable fluids on the suppression of opioid withdrawals in the opioid-dependent rats was studied. Physical dependence was induced by administration of morphine over a period of 6 days. Withdrawals were precipitated with naloxone (1 mg/kg, s.c.) 4 h after the last morphine injection on the 6th day. Test drugs (10-30% sucrose solution) were given orally for 2 h prior to naloxone-induced withdrawal in 14 h water deprived rats. Somatic signs of withdrawals were scored by using the global Gellert-Holtzman rating scale. Animals pretreated with low doses of sucrose solution (10-15%) did not produce any effect on the global withdrawal scale whereas a significant decrease on the global withdrawal scores was observed at higher doses of sucrose solution (20-30%) as compared to the controls. All the individual behavioral signs of withdrawals were significantly suppressed in a dose-related manner at higher doses of sucrose solutions whereas minimal suppression was observed for facial fasciculation/teeth chattering. These findings provide support that ingestion of high concentrations of sucrose solutions for shorter duration may activate the endogenous opioid system and appears to have an important role in modifying morphine withdrawals.

Utility of thin layer chromatography for detection of opioids and benzodiazepines in a clinical setting

This study examined the utility of thin layer chromatography (TLC) for detection of recent use of opioids and benzodiazepines among drug addicts seeking treatment at the Drug Dependence Treatment Centre of All India Institute of Medical Sciences, New Delhi, India. Over a period of 5 years (1991-1995), 6,055 urine samples were analyzed for opioids (morphine, codeine, buprenorphine, dextropropoxyphene, pentazocine) and benzodiazepines (diazepam, nitrazepam) by TLC. Out of all the drug tests (n = 9,922) carried out, 24% of the drugs had been used during the past 72 hr. Averaged across all drugs, the detection rates corresponding to 24, 48, and 72 hr by TLC were 37%, 36%, and 31%, respectively. A high percentage of negative TLC results was observed in these samples. Moderate sensitivity of the TLC assay procedure, low consumption of drug, short time between drug use and urine collection, overreporting by the subjects, and drug use history of the subject obtained from multiple sources led to high negative results. These findings suggest that all the TLC negative results also need further confirmation by an alternative, more sensitive technique in a clinical setting. This will make the drug abuse testing program more meaningful.

Caffeine induces differential cross tolerance to the amphetamine-like discriminative stimulus effects of dopaminergic agonists

The purpose of this study was to determine if caffeine induces cross tolerance to the amphetamine-like discriminative stimulus effects of dopaminergic drugs that act through distinct mechanisms (e.g., release, uptake inhibition, direct activation of dopamine D(1)- or D(2)-family receptors). Rats were trained to discriminate 1.0 mg/kg d-amphetamine from saline in a two-choice discrete-trial procedure. Stimulus-generalization curves were generated by cumulative dosing for d-amphetamine (0.1-1.0 mg/kg), methylphenidate (0.3-5.6 mg/kg), SKF 81297 (0.3-3.0 mg/kg), and R-(-)-propylnorapomorphine (NPA; 0.001-1.78 mg/kg), as well as for caffeine (3.0-56 mg/kg); curves were re-determined after twice daily injections of caffeine (30 mg/kg) for 3.5 days. The rats generalized dose dependently to the four dopaminergic drugs, but only to a limited extent to caffeine. Twice daily injections of caffeine induced significant cross tolerance (i.e., increased ED(50)) to the amphetamine-like discriminative effects of methylphenidate and SKF 81297, attenuated non-significantly the effects of NPA, and did not alter the effects of amphetamine. Thus, caffeine produces differential cross tolerance to the amphetamine-like discriminative effects of dopaminergic drugs, a phenomenon in which the dopamine D(1) receptor appears to have an important role.

Pharmacological Intervention of Nicotine Dependence

Nicotine dependence is a major cause of mortality and morbidity all over the world. Various medications have been tried to treat nicotine dependence including nicotine replacement therapy, bupropion, and varenicline. A newer venture to nicotine dependence treatment is a nicotine vaccine which is yet to get footsteps in common practice. The present review assimilates various pharmacotherapeutic measures to address nicotine dependence. However, it is to be noted that psychological interventions, when combined with pharmacotherapy, offer the greatest benefits to the patients.

Diagnostic clinical features of pentazocine‐induced ulcers

Background  Pentazocine was introduced in 1967 as a “non‐narcotic, nonaddicting” analgesic. However, the abuse potential of this medication was soon recognized, and cutaneous and muscular complications of pentazocine abuse have been reported.

Comparison of efficacy between buprenorphine and tramadol in the detoxification of opioid (heroin)-dependent subjects.

AIM/BACKGROUND Tramadol is a synthetic opiate and a centrally acting weak m-opioid receptor agonist. The potential advantages of tramadol include ease of administration, low abuse potential, and being nonscheduled. This study compared tramadol and buprenorphine for controlling withdrawal symptoms in patients with opioid dependence syndrome. METHODS Consenting male subjects between 20 and 45 years of age who fulfilled the ICD-10-DCR criteria for opiate dependence syndrome were randomly assigned in a double-blind, double-dummy placebo-controlled trial for detoxification. Those with multiple drug dependence, abnormal cardiac, renal and hepatic functions, psychosis, or organic mental illness were excluded. Assessments included Subjective Opiate Withdrawal Scale (SOWS), Objective Opiate Withdrawal Scale (OOWS), Visual Analog Scale (VAS), and Side Effect Check List. Subjects were evaluated daily and study duration was 10 days. RESULTS Sixty two subjects were enrolled. The mean SOWS and OOWS and VAS were significantly lower in the buprenorphine group on second and third day of detoxification as compared to the tramadol group. Although the retention rate was higher for buprenorphine group throughout the study, when compared with tramadol the difference was not significant on any day. Three subjects in the tramadol group had seizures. CONCLUSIONS Tramadol was found to have limited detoxification efficacy in moderate to severe opioid withdrawal and substantial risk of seizures as compared to buprenorphine. Further studies are warranted to examine its efficacy in mild opioid withdrawal symptoms and its potential use in outpatient settings where its administration advantages may be valuable.

The Role of NMDA Receptor Antagonists in Nicotine Tolerance, Sensitization, and Physical Dependence: A Preclinical Review

Nicotine, the primary psychoactive component of tobacco products, produces diverse neurophysiological, motivational, and behavioral effects through several brain regions and neurochemical pathways. Various neurotransmitter systems have been explored to understand the mechanisms behind nicotine tolerance, dependence, and withdrawal. Recent evidence suggests that glutamate neurotransmission has an important role in this phenomenon. The aim of the present review is to discuss preclinical findings concerning the role of N-methyl-D-aspartate (NMDA) receptor neurotransmission in mediating the behavioral effects of nicotine, tolerance, sensitization, dependence, and withdrawal. Based on preclinical findings, it is hypothesized that NMDA receptors mediate the common adaptive processes that are involved in the development, maintenance, and expression of nicotine addiction. Modulation of glutamatergic neurotransmission with NMDA receptor antagonists may prove to be useful in alleviating the symptoms of nicotine abstinence and facilitate tobacco-smoking cessation.

Effects of nitric oxide synthase inhibitors in attenuating nicotine withdrawal in rats

This study evaluates the effects of three nitric oxide synthase (NOS) inhibitors (L-NNA, L-NAME, L-NMMA) in attenuating the precipitated nicotine withdrawal syndrome in rats. Male albino Wistar rats were made dependent on nicotine by subcutaneous infusion of nicotine (9.0 mg/kg/day) via a 7 day osmotic pump, whereas control rats received saline via osmotic pumps. Test doses of each NOS inhibitor were administered 30 min prior to mecamylamine (1 mg/kg) challenge in control and test rats on the 7th day. Somatic signs of withdrawal were scored for 15 min by using the global Gellert-Holtzman rating scale followed by a measurement of motor activity. A comparison of NOS inhibitors treated rats with the mecamylamine-precipitated nicotine rats showed that at highest dose L-NNA appears to produce a more complete attenuation of all aspects of withdrawal syndrome. On the other hand, L-NAME appears to do so both at moderate and highest doses. This could be due to an incomplete reversal of some signs of withdrawals by L-NMMA. However, motor activity increased in nicotine dependent rats with the administration of NOS inhibitors. This study demonstrates that NO plays an important role in the expression of behavioral signs of nicotine withdrawal syndrome and suggests a potential use of NOS inhibitors as an aid in tobacco smoking cessation.

A Double-Blind Placebo-Controlled Randomized Trial of Varenicline for Smokeless Tobacco Dependence in India

INTRODUCTION The rate of smokeless tobacco use in India is 20%; its use causes serious health problems, and no trial has assessed behavioral or pharmacological treatments for this public health concern. This trial evaluated varenicline for treating smokeless tobacco dependence in India. METHODS This was a double-blind placebo-controlled randomized trial of varenicline (12 weeks, 1mg, twice per day) with 237 smokeless tobacco users in India. All participants received behavioral counseling. Outcomes included self-reported and biochemically verified abstinence at the end of treatment (EOT), lapse and recovery events, safety, and medication adherence. RESULTS Self-reported EOT abstinence was significantly greater for varenicline (43%) versus placebo (31%; adjusted odds ratio [AOR] = 2.6, 95% CI = 1.2-4.2, p = .009). Biochemically confirmed EOT abstinence was greater for varenicline versus placebo (25.2% vs. 19.5%), but this was not statistically different (AOR = 1.6, 95% CI = 0.84-3.1, p = .15). Compared with placebo, varenicline did not reduce the risk for a lapse (hazard ratio [HR] = 0.86, 95% CI = 0.69-1.1, p = .14), but it did increase the likelihood of recovery to abstinence (HR = 1.2, 95% CI = 1.02-1.4, p = .02). Greater adherence increased EOT cessation rates for varenicline (39% vs. 18%, p = .003) but not for placebo (28% vs. 14%, p = .06). There were no significant differences between varenicline and placebo in rate of side effects, serious adverse events, hypertension, or stopping or reducing medication. CONCLUSIONS Varenicline is safe for treating smokeless tobacco dependence in India, and further examination of this medication for this important public health problem is warranted.