Branched chain amino acids decrease tardive dyskinesia symptoms

Rationale: Prior studies had suggested (a) that a lessened ability to clear ingested forms of the large neutral amino acid (LNAA), phenylalanine (Phe), was associated with having tardive dyskinesia (TD), and (b) that greater availability of a group of LNAA, the branched chain amino acids (BCAA), concomitant with the lower availability of Phe to the brain are associated with a decrease in TD symptoms. The present study was then conducted to test whether increasing the daily intake of the BCAA would decrease the symptoms of TD. Methods: A 2-week trial of a BCAA medical food administered three times a day was conducted in nine men with long neuroleptic treatment histories. Frequency counts of TD movements were collected by videotape throughout the trial and these tapes were analyzed in blind random sequence for both patient and time for TD symptom level changes subsequent to completion of the trial. Plasma levels of the LNAA were also collected throughout the trial. Results: A statistically significant decrease in the level of TD symptoms was observed for the sample. The symptom changes were also clinically significant in that six of the nine subjects had symptom decreases of at least 58%, with all subjects having a decrease of at least 38%. BCAA administration increased plasma BCAA concentrations and BCAA/LNAA ratios and decreased plasma Phe concentrations and the Phe/LNAA ratio. Analyses indicated a strong significant correlation between the percent increase in the plasma BCAA values at the first administration and the percent improvement in TD over the trial in eight of the nine subjects. Conclusions: The BCAA show promise as a treatment for TD. The decrease in TD symptoms seen in the trial may have been modulated by the BCAA treatment-induced increased availability of the BCAA and decreased availability of Phe to the brain. Received: 13 August 1998/Final version: 14 December 1998     

Non-response to citalopram in depressive patients: pharmacokinetic and clinical consequences of a fluvoxamine augmentation

The effect of comedication with fluvoxamine on the plasma concentrations of the enantiomers of citalopram and its metabolites in dextromethorphan/mephenytoin phenotyped patients pretreated with citalopram (CIT) was studied: seven female patients (45.1 ± 13.9 years) suffering from a major depressive episode [ICD-10: F _32.2 (n = 3 patients), F _33.2 (n = 2), F _32.10 (n = 1) or F _32.11 (n = 1)] , who were non-responders to a 3-week treatment with 40 mg/day CIT (From day-21 to day 0) (day 0: MADRS score ≥12), were comedicated for another 3 weeks with fluvoxamine (50 mg/day from day 1–7, 100 mg/day from day 14–21). All patients were extensive metabolizers of mephenytoin (CYP2C19) and dextromethorphan (CYP2D6), except one patient, who had a genetic deficiency of CYP2D6. There was a significant increase of the plasma concentrations of S- and R-citalopram from day 0 (27 ± 14 μg/l and 55 ± 23 μg/l, respectively) to day 21 (83 ± 38 μg/l and 98 ± 44 μg/l, respectively), after addition of fluvoxamine (P < 0.02, for each comparison), and the mean ratio S/R-citalopram increased from 0.48 to 0.84. S-Citalopram inhibits more potently 5-HT uptake than R-citalopram: therefore, fluvoxamine increases the pharmacologically more active S-citalopram with some stereoselectivity. According to a previous in vitro study, this pharmacokinetic interaction occurs on the level of CYP2C19, but also of CYP2D6 and CYP3A4 which, in contrast to CYP1A2, contribute to the N-demethylation of citalopram and which are stereoselectively inhibited by fluvoxamine. All but one patient showed clinical improvement by a decrease of the MADRS score by at least 50% and a final score ≤13 (mean ± SD: day 0:30.6 ± 9.2; day 21:11.0 ± 6.5). Some patients showed minor symptoms, such as nausea and tremor, but the combined treatment was generally well tolerated. Received: 29 May 1996 /Final version: 2 September 1996     

Discriminative stimulus effects of S(−)–methcathinone (CAT): a potent stimulant drug of abuse

Methcathinone (“CAT”) is a CNS stimulant that is a very significant drug of abuse in the former Soviet Union. It has also appeared on the clandestine market in the United States and has been recently classified as a Schedule I substance. In the present study, S(−)-methcathinone [S(−)-CAT, 0.50 mg/kg, IP] was employed as the training drug in a two-lever drug discrimination task in rats. Once established, the S(−)-CAT stimulus was shown to have a rapid onset to action (within 5 min) and a duration of effect of approximately 60–90 min. In tests of stimulus generalization (substitution), the S(−)-CAT (ED₅₀ = 0.11 mg/kg) stimulus generalized to S(+)-methamphetamine (ED₅₀ = 0.17 mg/kg), S(−)-cathinone (ED₅₀ =  0.19 mg/kg), S(+)-amphetamine (ED₅₀ = 0.23 mg/kg), aminorex (ED₅₀ = 0.27 mg/kg), (±)-CAT (ED₅₀ = 0.25 mg/kg), (±)-cathinone (ED₅₀ = 0.41 mg/kg), R(+)-CAT (ED₅₀ = 0.43 mg/kg), cis-4-methylaminorex (ED₅₀ = 0.49 mg/kg), methylphenidate (ED₅₀ = 0.83 mg/kg), and cocaine (ED₅₀ = 1.47 mg/kg). S(−)-CAT-stimulus generalization did not occur to fenfluramine, a structurally related nonstimulant anorectic. Lastly, haloperidol (AD₅₀ = 0.18 mg/kg), a dopamine receptor antagonist, potently antagonized the S(−)-CAT stimulus. It is concluded that S(−)-methcathinone is a very potent CNS stimulant, which appears to produce its stimulus effect, at least in part, via a dopaminergic mechanism. Received: 4 August 1997/Final version: 27 March 1998     

Scopolamine impairs the ability of parturient ewes to learn to recognise their lambs

Within a 4-h period after parturition, the ewe learns the odor of her lamb that will later allow recognition of her offspring from an alien lamb. This study investigated the involvement of the cholinergic system in this olfactory learning. At parturition and 2 h later, ewes received IM injections of saline (C group, n = 21), scopolamine methylbromide (METSCOP group, 100 μg/kg, n = 14) a peripherally acting muscarinic antagonist, a low dose of scopolamine hydrobromide (SCOP32 group, 32 μg/kg, n = 15) or a higher dose of scopolamine hydrobromide (SCOP100 group, 100 μg/kg, n = 18). Maternal behavior was observed at parturition and selective behavior was tested after 4 h of mother-young contact. No differences in maternal behavior at parturition were found between groups. By contrast, the proportion of ewes showing selectivity was significantly lower in the SCOP100 group (7/18) than in the METSCOP group (12/14, P = 0.01), SCOP32 group (12/15, P = 0.03), or C group (17/21, P = 0.01). In addition, saline-treated ewes, after having established their selective bond, received 100 μg/kg scopolamine and were again tested for selectivity 20 min later. Only one out of the 17 tested ewes failed to recognize their lambs after this treatment. These results indicate that intact central muscarinic transmission of the brain is required for the learning of individual lamb odor at parturition but not for the recall of this information. Received: 1 July 1996/Final version: 12 September 1996     

Phenacetin O-deethylation by human liver microsomes in vitro: inhibition by chemical probes,SSRI antidepressants,nefazodone and venlafaxine

Biotransformation of phenacetin via O-deethylation to acetaminophen, an index reaction reflecting activity of Cytochrome P450-1A2, was studied in microsomal preparations from a series of human livers. Acetaminophen formation was consistent with a double Michaelis-Menten system, with low-K_m (mean K_m1 = 68 μM) and high-K_m (mean K_m2 = 7691 μM) components. The low-K_m enzyme accounted for an average of 96% of estimated intrinsic clearance, and was predicted to contribute more than 50% of net reaction velocity at phenacetin concentrations less than 2000 μM. Among index inhibitor probes, α-naphthoflavone was a highly potent inhibitor of the low-K_m enzyme (K_i1 = 0.013 μM); furafylline also was a moderately active inhibitor (K_i1 = 4.4 μM), but its inhibiting potency was increased by preincubation with microsomes. Ketoconazole was a relatively weak inhibitor (K_i1 = 32 μM); quinidine and cimetidine showed minimal inhibiting activity. Among six selective serotonin reuptake inhibitor (SSRI) antidepressants, fluvoxamine was a potent inhibitor of 1A2 (mean K_i1 = 0.24 μM). The other SSRIs were more than tenfold less potent. Mean K_i1 values were: fluoxetine, 4.4 μM; norfluoxetine, 15.9 μM; sertraline, 8.8 μM; desmethylsertraline, 9.5μM; paroxetine, 5.5 μM. The antidepressant nefazodone and four of its metabolites (meta-chloro-phenylpiperazine, two hydroxylated derivatives, and a triazoledione) were very weak inhibitors of P450-1A2. Venlafaxine and its O- and N-desmethyl metabolites showed minimal inhibitory activity. Received: 18 March 1996/Final version: 10 July 1996     

The cholecystokinin-B receptor antagonist CI-988 failed to affect CCK-4 induced symptoms in panic disorder patients

The effects of the cholecystokinin-B (CCK-B) receptor antagonist CI-988 on symptoms elicited by the cholecystokinin tetrapeptide (CCK₄) were studied in DSM-IIIR patients with panic disorder. The study employed a double-blind, two-period incomplete block design. Patients (n = 14) received two different dosages of CI-988 (50 mg or 100 mg) or placebo 2 h prior to an IV bolus injection of CCK₄ (20 μg) on two separate occasions. The primary efficacy parameter was the total intensity score on the Panic Symptoms Scale (PSS). Secondary parameters were the number of panic symptoms, time to and occurrence of the first panic symptoms, duration of symptoms, intensity of apprehension and the percentage of patients who did not have a panic attack. The PSS failed to show a statistically significant treatment effect on any of these outcome measures. The average panic rate was 50%, 14.3% and 37.5% after placebo, 50 and 100 mg CI-988, respectively. The differences in panic rate were not statistically significant. The results of this study suggest that CI-988 in doses up to 100 mg is not effective in reducing symptoms of panic anxiety induced by CCK₄. Received: 13 May 1996/Final version: 27 September 1996     

Relationship between the CYP2D6 genotype and the steady-state plasma concentrations of trazodone and its active metabolite m-chlorophenylpiperazine

The relationship between the cytochrome P450 (CYP) 2D6 genotype and the steady-state plasma concentrations (Css) of trazodone and its active metabolite m-chlorophenylpiperazine (mCPP) was studied in 54 depressed Japanese patients receiving trazodone 150 mg at bedtime. By use of allele-specific PCR analysis, the wild type allele, three mutated alleles causing absent enzyme activity (CYP2D6A, CYP2D6B and CYP2D6D) and one mutated allele causing decreased enzyme activity (CYPZD6 Ch) were identified. The means (ranges) of the Css of trazodone, corrected to the median body weight in 17 cases with no mutated allele, 27 cases with one mutated allele and 10 cases with two mutated alleles, were 556 (281–1115), 643 (302–1362) and 671 (234–1418) ng/ml, respectively, while the values of mCPP were 60 (35–121), 65 (33–99) and 58 (38–112) ng/ml, respectively. Neither the Css of trazodone (F = 0.80, P = 0.45) nor that of mCPP (F = 0.49, P = 0.61) significantly differed among the three groups. The present study thus suggests that the CYP2D6 genotype cannot predict the Css of these compounds. Received: 24 January 1997/Final version: 26 March 1997     

Human cytochromes mediating N-demethylation of fluoxetine in vitro

Biotransformation of the selective serotonin reuptake inhibitor antidepressant, fluoxetine, to its principal metabolite, norfluoxetine, was evaluated in human liver microsomes and in microsomes from transfected cell lines expressing pure human cytochromes. In human liver microsomes, formation of norfluoxetine from R,S-fluoxetine was consistent with Michaelis-Menten kinetics (mean K_m = 33 μM), with evidence of substrate inhibition at high substrate concentrations in a number of cases. The reaction was minimally inhibited by coincubation with chemical probes inhibitory for P450-2D6 (quinidine), -1A2 (furafylline, α-naphthoflavone), and -2E1 (diethyldithiocarbamate). Substantial inhibition was produced by coincubation with sulfaphenazole (K_i = 2.8 μM), an inhibitory probe for P450-2C9, and by ketoconazole (K_i = 2.5 μM) and fluvoxamine (K_i = 5.2 μM). However, ketoconazole, relatively specific for P450-3A isoforms only at low concentrations, reduced norfluoxetine formation by only 20% at 1 μM, and triacetyloleandomycin (≥ 5 μM) reduced the velocity by only 20–25%. Microsomes from cDNA-transfected human lymphoblastoid cells containing human P450-2C9 produced substantial quantities of norfluoxetine when incubated with 100 μM fluoxetine. Smaller amounts of product were produced by P450-2C19 and -2D6, but no product was produced by P450-1A2, -2E1, or 3A4. Cytochrome P450-2C9 appears to be the principal human cytochrome mediating fluoxetine N-demethylation. P450-2C19 and -3A may make a further small contribution, but P450-2D6 is unlikely to make an important contribution. Received: 23 December 1996 / Final version: 4 March 1997     

Antidepressant treatment in helpless rats: effect on the electrophysiological activity of raphe dorsalis serotonergic neurons

Chronic treatment with antidepressants renders serotonergic neuronal firing less sensitive to the inhibitory effect of serotonin (5-HT) reuptake blockers in the rat, and this has been considered as a major correlate of the therapeutic action of these drugs. We investigated whether the same mechanisms could be evidenced in an experimental model of depression, the learned helplessness paradigm. Rats rendered helpless by a single session of inescapable electrical footshocks exhibit, for several days, depression-like behavioural deficits which can be reversed by sub-chronic, but not acute, treatment with antidepressants. Recording of serotonergic neurons in the dorsal raphe nucleus revealed that, under baseline conditions, the spontaneous firing was similar in helpless rats and in non-helpless controls. However, neurons in the former group exhibited an enhanced sensitivity to the inhibitory action of the 5-HT reuptake blocker, citalopram (ED₅₀ = 0.18 ± 0.02 mg/kg IV in helpless rats versus 0.27 ± 0.03 mg/kg IV in controls, P < 0.05). Treatment with zimeldine during 3 consecutive days induced in both helpless and control rats, a decrease in the inhibitory response of serotonergic neurons to the citalopram challenge, which resulted in a normalization of the neuronal reactivity in the helpless group (ED₅₀ = 0.31 ± 0.03 mg/kg IV). Since this adaptive phenomenon parallels the behavioural improvement induced by the repeated administration of zimeldine and other antidepressants in helpless rats, it might be considered as a crucial event in the mechanism of therapeutic action of these drugs. Received: 14 August 1996 / Final version: 4 November 1996     

A comparison of bd and tid dose regimens of quetiapine (Seroquel) in the treatment of schizophrenia

Quetiapine (Seroquel, ICI 204,636) is an atypical antipsychotic that is effective in the treatment of both positive and negative symptoms of schizophrenia, and has a low propensity to cause extrapyramidal symptoms. The compound has a relatively short plasma elimination half-life (approximately 7 h). However, since dopamine D₂ receptor occupancies correlate poorly with plasma concentrations of antipsychotics, plasma elimination half-life may not predict either duration of clinical effect or dosing frequency. Accordingly, the efficacy and tolerability of three dosing regimens (450 mg/day given in two or three divided doses daily, and 50 mg/day given twice daily) were compared in a 6-week, double-blind, randomized, multicentre, parallel-group study. The study recruited hospitalized men and women aged 18–65 years meeting DSM-IIIR criteria for acute exacerbation of chronic or subchronic schizophrenia. Six hundred and eighteen patients were randomly assigned to treatment with quetiapine 150 mg tid (n = 209), 225 mg bd (n = 200), or a comparator dose of 25 mg bd (n = 209). At day 42, the last day of randomized treatment and the primary timepoint for efficacy, quetiapine 450 mg/day was more effective than 50 mg/day: 225 mg bd was consistently superior to 25 mg bd in all measures of efficacy (total BPRS, P = 0.006; CGI severity, CGI improvement and SANS, P < 0.03), and 150 mg tid was statistically significantly superior to 25 mg bd with respect to BPRS total score (P = 0.05). The 225 mg bd and 150 mg tid groups were not significantly different from each other with respect to any efficacy measure. Quetiapine was generally well tolerated. Extrapyramidal symptom (EPS) adverse events were generally rare, and occurred with similar frequencies in the two 450 mg/day groups. Quetiapine was not associated with sustained increases in plasma prolactin at any dose. These data support the atypical profile developed from preclinical studies and show that quetiapine is an effective, well tolerated antipsychotic that can be given twice daily. Received: 16 May 1997/Final version: 13 October 1997     

Efficacy and safety of spirapril,a new ace-inhibitor,in elderly hypertensive patients

Objective: To compare the safety, efficacy, tolerability and duration of the antihypertensive effect of an ACE-inhibitor spirapril 3 mg or 6 mg in elderly (≥ 60 y) hypertensive patients in a multicentre, observational, double-blind randomised study. Methods: After a four-week placebo period, 39 patients were randomised to six weeks of treatment with spirapril 3 mg and 47 patients with spirapril 6 mg. Results: In the sitting position the mean (SD) decrease in systolic blood pressure (SBP) was 12(15) mmHg (95% confidence interval 7 to 17 mmHg) and in dia- stolic blood pressure (DBP) 10(7) mmHg (8 to 12 mmHg) in the 3-mg group and 10(13) mmHg (6 to 14 mmHg) and 9(7) mmHg (7 to 11 mmHg), respectively, in the 6-mg group (P < 0.001 compared to placebo period in both groups). Spirapril 3mg and 6 mg produced DBP ≤ 90 mmHg or a fall ≥ 10 mmHg in 53% and 51% of the patients, respectively. DBP was ≤ 90 mmHg in 36% and SBP ≤ 160 mmHg in 67% of the patients taking 3 mg and in 26% and 63% of the patients taking 6 mg spirapril. The most commonly reported adverse effects were cough (13–17%), dizziness, headache and insomnia. A trend to a more frequent adverse effects was observed in patients receiving spirapril 6 mg. Spirapril was both cholesterol- and glucose-neutral. Conclusion: According to our study, spirapril 3mg seems to be a suitable starting dose for the treatment of hypertension in the elderly patients. Received: 8 August 1995/Accepted in revised form: 7 November 1995     

Rated well-being in relation to plasma concentrations of l- and d-methadone in satisfied and dissatisfied patients on methadone maintenance treatment

Rationale: One of the major problems in methadone maintenance treatment is to find optimal individual doses for the patients. Objective: The present study investigated whether the use of rating scales together with enantioselective analysis of l-methadone might facilitate dose adjustments in a clinical situation. Methods: Rating scales were used to evaluate subjective and objective signs of well-being in relation to plasma methadone concentrations in two groups of patients receiving methadone maintenance treatment. The first group (n = 25) was well-adjusted according to clinical observations and were satisfied with their methadone doses (86.2 ± 4.3 mg). The second group (n = 25) was in need of the methadone dose adjustment; they complained of low dosing, despite a dose level of 69.2 ± 4.0 mg/day. Results: Results indicated a significant correlation between dose and methadone concentration among dissatisfied patients only. The trough levels of d,l-methadone and l-methadone, as well as their elimination rates, were similar in the two groups of patients. There was a variable predominance of l- over d-methadone in plasma (ratio ≈1.2; range 0.7–3.6). Illicit use of drugs by the patients was related to the methadone dose and to satisfaction with the dose received. Increased illicit drug use among dissatisfied patients was successfully eliminated by raising the methadone dose. Subjective and objective ratings of the satisfied patients were quite stable throughout the evaluation period, whereas the ratings of the dissatisfied patients were unstable. These patients seemed to be more sensitive to low trough levels of methadone than the satisfied patients. Associations between the subjective and objective ratings and plasma methadone, along with background characteristics, were characterized by multiple regression analyses. The plasma concentrations of l-methadone were one of the most important explanatory variables in these analyses. Associations between well-being and methadone concentrations in plasma were stronger for l-methadone than for d,l-methadone. Conclusions: Selective measurements of the active isomer and the use of rating scales should be of clinical value when monitoring methadone maintenance treatment patients. Received: 17 June 1998/Final version: 10 December 1998     

Effect of fluvoxamine on platelet 5-HT2A receptors as studied by [3H]lysergic acid diethylamide ([3H]LSD) binding in healthy volunteers

Alterations in platelet 5-HT_2A receptor characteristics have been reported in major depression as well as in other psychiatric diseases, and some effort has been made to utilize platelet 5-HT_2A receptor status as a biological correlate to antidepressant drug response. In order to investigate whether treatment with a selective serotonin reuptake inhibitor affects platelet 5-HT_2A receptors, we have studied platelet [³H]lysergic acid diethylamide ([³H]LSD) binding in healthy subjects treated with fluvoxamine in increasing dosage once weekly for 4 weeks. After 1 week of fluvoxamine treatment (25 mg/day), both B_max and K_d were significantly lower than before the start of the treatment (19.9 versus 25.5 fmol/mg protein, P = 0.005 for B_max; 0.45 versus 0.93 nM, P = 0.006 for K_d). B_max returned to baseline during week 2, whereas K_d was lower than the baseline value throughout the treatment period. After discontinuation of fluvoxamine treatment, there was a significant increase in K_d (0.50 nM before discontinuation vs. 1.14 nM after discontinuation; P = 0.001), but not in B_max. The study demonstrates that fluvoxamine affects platelet 5-HT_2A receptor status irrespective of underlying psychiatric disease, and that this effect is evident already after 1 week at a subtherapeutic fluvoxamine dose. Received: 11 October 1996/Final version: 12 March 1997     

Effects of ketoprofen and ibuprofen on platelet aggregation and prostanoid formation in man

Objective: In the present randomized, four-way crossover study we determined the effects of two oral doses each of ketoprofen and ibuprofen on platelet aggregation and prostanoid formation in man. Methods: Twelve healthy female volunteers received for 2 consecutive days, followed by a 5-day drug-free interval, one of the following: ketoprofen 3 × 25 mg per day, or ketoprofen 3 × 50 mg per day, or ibuprofen 3 × 200 mg per day, or ibuprofen 3 × 400 mg per day. The response criteria, determined before and on the 2nd day of each treatment period, were: maximal platelet aggregation in response to 1.0 mmol ⋅ l^–1 arachidonic acid measured by the method of Born and Cross, thromboxane B₂ (TXB₂) concentration in platelet-rich plasma after aggregation measured by radioimmunoassay, and PGE-M, the index metabolite of total body prostaglandin E₂ (PGE₂) production, assessed by gas chromatography/tandem mass spectrometry using ¹⁸O₂-PGE-M as internal standard. Results: Platelet aggregation was significantly reduced by ketoprofen 3 × 25 mg per day (−57%) and ketoprofen 3 × 50 mg per day (−85%) as compared to control, whereas ibuprofen 3 × 200 mg per day (−3%) and ibuprofen 3 × 400 mg per day (−22%) had no significant effects. TXB₂ synthesis was significantly decreased by ketoprofen 3 × 25 mg per day (−72%), ketoprofen 3 × 50 mg per day (−97%) and ibuprofen 3 × 400 mg per day (−48%) as compared to control; ibuprofen 3 × 200 mg per day did not reduce TXB₂ formation significantly (−23%). All four treatments reduced 24-h urinary excretion of PGE-M significantly in the range of−39% (ketoprofen 3 × 25 mg per day) to −53% (ibuprofen 3 × 400 mg per day) without significant differences between treatments. Conclusion: Our data show that both ketoprofen dosages were more effective in inhibition of platelet aggregation and platelet thromboxane synthesis than ibuprofen in low or high dosage. Total body synthesis of the E-prostaglandins was inhibited by all drug schedules without significant differences between treatments. Received: 26 January 1996;/Accepted in revised form: 11 June 1996     

Specific attentional dysfunction in adults following early start of cannabis use

Rationale and objective: The present study tested the hypothesis that chronic interference by cannabis with endogenous cannabinoid systems during peripubertal development causes specific and persistent brain alterations in humans. As an index of cannabinoid action, visual scanning, along with other attentional functions, was chosen. Visual scanning undergoes a major maturation process around age 12–15 years and, in addition, the visual system is known to react specifically and sensitively to cannabinoids. Methods: From 250 individuals consuming cannabis regularly, 99 healthy pure cannabis users were selected. They were free of any other past or present drug abuse, or history of neuropsychiatric disease. After an interview, physical examination, analysis of routine laboratory parameters, plasma/urine analyses for drugs, and MMPI testing, users and respective controls were subjected to a computer-assisted attention test battery comprising visual scanning, alertness, divided attention, flexibility, and working memory. Results: Of the potential predictors of test performance within the user group, including present age, age of onset of cannabis use, degree of acute intoxication (THC+THCOH plasma levels), and cumulative toxicity (estimated total life dose), an early age of onset turned out to be the only predictor, predicting impaired reaction times exclusively in visual scanning. Early-onset users (onset before age 16; n = 48) showed a significant impairment in reaction times in this function, whereas late-onset users (onset after age 16; n = 51) did not differ from controls (n = 49). Conclusions: These data suggest that beginning cannabis use during early adolescence may lead to enduring effects on specific attentional functions in adulthood. Apparently, vulnerable periods during brain development exist that are subject to persistent alterations by interfering exogenous cannabinoids. Received: 15 June 1998/Final version: 30 September 1998     

Doxepin and its metabolites in plasma and cerebrospinal fluid in depressed patients

Little information exists on the concentrations of antidepressants and their metabolites in CSF. We measured plasma and CSF levels of trans-doxepin (trans-DOX) and DOX metabolites in 12 depressed patients treated with DOX (250 mg/day) for 6 days. Spinal taps and blood samples were taken on day 7, 10 h after drug administration. Trans-DOX, cis-desmethyldoxepin (cis-DM-DOX), trans-desmethyldoxepin (trans-DM-DOX) and di-desmethyldoxepin (DDM-DOX) were analyzed in CSF and plasma samples by HPLC with column-switching. Although DOX was given as a mixture of 85% trans-DOX and 15% of the pharmacologically more active cis-DOX, we found similar amounts of cis-DM-DOX and trans-DM-DOX in plasma (59.8 ± 45.1 versus 72.0 ± 60.0 ng/ml; NS), suggesting that isomerization of DOX had taken place. Trans-DOX and DOX metabolites could be detected in CSF of most patients. Relatively low CSF concentrations of the active metabolite cis-DM-DOX were measured. Clinical efficacy, as assessed by HAMD scores, was not significantly related to plasma or CSF concentrations of trans-DOX or its metabolites. Trans-DOX and DOX metabolites were distributed differently between plasma and CSF. It is concluded that isomerization of DOX is not only relevant for neuronal uptake inhibition, but also for the transport of the metabolites. Received: 13 May 1996/Final version: 16 December 1996     

Temporal effects of nicotine nasal spray and gum on nicotine withdrawal symptoms

Nicotine nasal spray and nicotine gum have been found to be effective in relieving nicotine withdrawal symptoms. In this randomized single-blind study, 91 cigarette smokers were randomly assigned to a single 1 mg dose of active nicotine nasal spray (n = 29), active 4 mg nicotine gum (n = 31), saline placebo nasal spray (n = 16) or placebo gum (n = 15). Following overnight abstinence, subjects repeatedly completed visual analog scales for assessing nicotine withdrawal symptoms over 30 min preceding (time -30 min to time 0) and 120 min following a single dose of study medication. This sequence was performed 3 times during the day. Nicotine withdrawal symptoms were assessed on a 41-point visual analog scale (1 = no withdrawal, 41 = extreme withdrawal). At the initial session only, blood samples for serum nicotine levels were taken at baseline, then at 5, 10, 30 and 120 min following study drug administration. The mean (± SD) age of the subjects was 38.6 (±10.1) years, 48% were females, smoking rate was 24.5 (±7.8) cigarettes per day, and years of smoking was 19.9 (±10.0). A single 1 mg dose of nicotine nasal spray provided more immediate relief for craving for a cigarette compared to a single 4 mg dose of nicotine gum. Serum venous nicotine levels for the active nicotine nasal spray and nicotine gum were comparable at 5 and 10 min while the levels were higher for nicotine gum at 30 and 120 min. Changes in withdrawal symptoms were not found to be related to serum venous nicotine levels. Our findings provide a rationale for the as needed use of nicotine nasal spray to control withdrawal symptoms, possibly in combination with other medications with longer acting effects. Received: 18 February 1998/Final version: 1 May 1998     

Effect of the selective serotonin reuptake inhibitor fluvoxamine on CCK-4 induced panic attacks

Data from animal studies suggest a functional relationship between the cholecystokinin-ergic (CCK) and the serotonergic (5-HT) system. There is increasing evidence that the cholecystokinin-4 (CCK₄) challenge test could be a valid experimental model for panic attacks in man. The aim of the present study is twofold; 1) to validate this model further and 2) to shed more light on the putative CCK\5-HT interaction. To this end, we studied the effect of the selective serotonin reuptake inhibitor (SSRI) fluvoxamine on CCK₄-induced panic attacks. Twenty-six panic disorder (PD) patients received, before and after a double blind 8-week treatment period with fluvoxamine (n = 17) or placebo (n = 9), a single blind bolus injection with 50 μg CCK₄. Treatment with fluvoxamine (150 mg daily) significantly decreased the sensitivity of PD patients for CCK₄ while placebo was without effect. Of the patients who responded to treatment, 83% no longer experienced a panic attack when rechallenged with CCK₄, whereas in the non-responders group this was only 28%. In the fluvoxamine group the treatment response evaluated by the Hamilton Anxiety Scale (HAS) showed a statistically significant treatment effect. The results of this study strengthen the validity of the CCK₄ test as an experimental human model for panic attacks and yield evidence supporting the hypothesis that both CCK and serotonin are implicated in the regulation of anxiety. Received: 15 April 1996/Final version: 27 September 1996     

Clozapine metabolism rate as a possible index of drug-induced granulocytopenia

A possible relationship between haematological adverse reactions and clozapine (CLZ) metabolism rate was studied. Sixteen chronic schizophrenic outpatients (mean age 34.62 years ± 7.56 SD) were treated with CLZ, 75–600 mg/daily for 9 weeks. CLZ and norclozapine (NCLZ) plasma levels were determined weekly, contemporarily with blood cell counts.  CLZ plasma levels ranged from 25 to 1270 ng/ml (mean 266.27 ng/ml ± 197.44 SD), while NCLZ plasma levels ranged from 25 to 1280 ng/ml (mean 169.0 ng/ml ± 127.94 SD). NCLZ/CLZ ratio ranged from 0.13 to 1.72 (mean 0.72 ± 0.28 SD). Leukocyte count ranged from 5.2 to 18.8 10⁹/l (mean 9.37 10⁹/l ± 2.94 SD) and neutrophil count ranged from 1.8 to 13.4 10⁹/l (mean 5.73 ± 2.57 SD). No correlation was found between CLZ dosage and NCLZ plasma levels. Both CLZ and NCLZ plasma levels correlated positively with neutrophil count (CLZ: P = 0.001, r = 0.26; NCLZ: P = 0.01, r = 0.20). The correlation between NCLZ/CLZ plasma level ratio and neutrophil count was significantly negative (P = 0.002, r  = 0.25). These preliminary data suggest that the NCLZ/CLZ ratio, as an index of CLZ metabolism, might be a possible risk factor associated with CLZ treatment. Received: 15 May 1997/Final version: 3 October 1997     

Naltrexone administration affects ad libitum smoking behavior

Endogenous opioid peptides have been implicated in the reinforcement of smoking and opioid antagonists have been examined to determine their role in smoking behavior. To date, the relationship between smoking behavior and chronic opiate antagonist administration during ad libitum smoking has not been investigated. The purpose of this study was to examine the relationships between naltrexone, an opiate antagonist administered orally, and smoking behavior and mood states during ad libitum smoking. A repeated measures experimental design was used. Normal adult male and female volunteers, admitted to the Clinical Research Center, were randomly assigned to naltrexone-treated (n = 22) or placebo-control (n = 21) groups in a double-blind manner. Day 1 was considered acclimation to the unit and day 2 was baseline, or pre-drug administration. On days 3, 4, and 5, subjects received 50 mg naltrexone or a placebo at 0700 and 1600 hours. Plasma nicotine and expired air carbon monoxide levels were measured daily at 1900 hours. Number of cigarettes smoked, mood states, withdrawal symptomatology and self-reported satisfaction with smoking were also quantified daily. Results indicated that plasma nicotine levels (P = 0.005), number of cigarettes smoked daily (P = 0.003) and self-reported satisfaction with smoking (P = 0.043) were significantly lower among those treated with naltrexone, compared to the placebo-control group. Expired air carbon monoxide levels did not differ between the two groups. In addition, mood states and withdrawal symptoms did not differ between groups. These findings suggest that endogenous opioid peptides influence specific smoking behavior variables. Received: 7 November 1997/ Final version: 7 April 1998