Evidence that formulations of the selective MAO-B inhibitor, selegiline, which bypass first-pass metabolism, also inhibit MAO-A in the human brain.

Selegiline (L-deprenyl) is a selective, irreversible inhibitor of monoamine oxidase B (MAO-B) at the conventional dose (10 mg/day oral) that is used in the treatment of Parkinson's disease. However, controlled studies have demonstrated antidepressant activity for high doses of oral selegiline and for transdermal selegiline suggesting that when plasma levels of selegiline are elevated, brain MAO-A might also be inhibited. Zydis selegiline (Zelapar) is an orally disintegrating formulation of selegiline, which is absorbed through the buccal mucosa producing higher plasma levels of selegiline and reduced amphetamine metabolites compared with equal doses of conventional selegiline. Although there is indirect evidence that Zydis selegiline at high doses loses its selectivity for MAO-B, there is no direct evidence that it also inhibits brain MAO-A in humans. We measured brain MAO-A in 18 healthy men after a 28-day treatment with Zydis selegiline (2.5, 5.0, or 10 mg/day) and in 3 subjects receiving the selegiline transdermal system (Emsam patch, 6 mg/day) using positron emission tomography and the MAO-A radiotracer [(11)C]clorgyline. We also measured dopamine transporter (DAT) availability in three subjects from the 10 mg group. The 10 mg Zydis selegiline dose significantly inhibited MAO-A (36.9±19.7%, range 11-70%, p<0.007)) but not DAT; and while Emsam also inhibited MAO-A (33.2±28.9 (range 9-68%) the difference did not reach significance (p=0.10)) presumably because of the small sample size. Our results provide the first direct evidence of brain MAO-A inhibition in humans by formulations of selegiline, which are currently postulated but not verified to target brain MAO-A in addition to MAO-B.

Treatment effects of selegiline transdermal system on symptoms of major depressive disorder: a meta-analysis of short-term, placebo-controlled, efficacy trials.

OBJECTIVE: Selegiline transdermal system (STS) is efficacious for the treatment of major depressive disorder (MDD). This meta-analysis explores treatment effects of STS for individual symptoms of MDD derived from line-item analyses of the 28-item Hamilton Rating Scale for Depression (HAM-D28) and the Montgomery-Asberg Depression Rating Scale (MADRS). METHODS: Change in score from baseline to end of treatment for each item of the HAM-D28 and MADRS was assessed using a multilevel model for meta-analysis of continuous outcome data from all five short-term, randomized, placebo-controlled efficacy trials conducted during preapproval clinical development of STS for MDD. Utilizing a random-effects model with trial effects fixed and adjusting for baseline scores, confidence intervals (95%) were computed for treatment differences between STS and placebo. RESULTS: STS exhibited significant treatment effects on core depression symptoms (HAM-D Bech-6 items: depressed mood, guilt, work and activities, retardation, psychic anxiety, general somatic symptoms), reverse vegetative symptoms (oversleeping, overeating), motoric retardation, suicide, and genital symptoms (libido). Significant STS treatment effects were also noted for each MADRS item except for reduced sleep and appetite. The most prominent MADRS effects were improvement in sadness, lassitude, and poor concentration. CONCLUSIONS: STS, an monoamine oxidase inhibitor antidepressant that potentiates the three major monoamine neurotransmitters (serotonin, norepinephrine, and dopamine), has beneficial therapeutic effects for a spectrum of individual symptoms rated by the HAM-D28 and MADRS. Analyses of specific symptoms assessed by depression rating scales can offer guidance to clinicians in individualizing drug therapy based on presenting symptoms.

Effects of a tyramine-enriched meal on blood pressure response in healthy male volunteers treated with selegiline transdermal system 6 mg/24 hour.

BACKGROUND: Monoamine oxidase inhibitors are well recognized as effective antidepressant agents but are rarely used due, in part, to the risk of hypertensive crisis following the ingestion of foods high in tyramine ("cheese reaction"). A selegiline transdermal system (STS) was developed to provide antidepressant concentrations of selegiline in the brain, while preserving the gastrointestinal monoamine oxidase A (MAO-A) barrier. The present study was conducted to determine the effect of the STS 6 mg/24 hour on cardiovascular safety following the ingestion of approximately 400 mg of tyramine consumed as a component of aged cheeses. METHODS: In this open-label, single-center phase I study, cardiovascular vital signs were recorded following tyramine challenges during placebo and STS 6 mg/24 hr treatment. Subjects were observed for clinical signs and symptoms of a pressor response and/or potential hypertensive crisis during and following the challenges. RESULTS: Ingestion of tyramine-enriched meals following 13 consecutive days of treatment with the STS 6 mg/24 hr (pharmacokinetic steady-state) produced no clinically significant changes in cardiovascular vital signs in 12 healthy adult male subjects. No evidence of a tyramine pressor effect on systolic blood pressure or evidence of hypertensive crisis occurred during the STS treatment. CONCLUSION: These results suggest that STS 6 mg/24 hr may be administered without concern for dietary tyramine consumption.

The effects of chronic treatment with the mood stabilizers valproic acid and lithium on corticotropin-releasing factor neuronal systems.

Corticotropin-releasing factor (CRF) plays a preeminent role in coordinating the endocrine, autonomic, and behavioral responses to stress. Dysregulation of both hypothalamic and extrahypothalamic CRF systems have been reported in patients with major depression and post-traumatic stress disorder. Moreover, effective treatment of these conditions leads to normalization of these CRF systems. Although there is virtually no data concerning alterations of CRF systems in bipolar disorder (manic depressive illness), previous work indicates that valproic acid, an anticonvulsant also effective in the treatment of acute mania, alters central CRF neuronal systems. In the current studies, we chronically administered valproic acid and lithium, two clinically effective mood stabilizers, in nonstressed rats to extend our previous findings. Chronic valproic acid administration decreased CRF mRNA expression in the paraventricular nucleus of the hypothalamus; lithium administration increased CRF mRNA expression in the central nucleus of the amygdala. Although valproic acid increased CRF(1) receptor mRNA expression in the cortex, CRF(1) receptor binding was decreased in both the basolateral amygdala and cortex, suggesting that chronic valproate treatment may in fact dampen the overall tone in this central stress pathway. Valproate treatment decreased CRF(2A) mRNA expression in both the lateral septum and hypothalamus, although CRF(2A) receptor binding was unchanged. Lithium administration decreased CRF(1) mRNA expression in both the amygdala and frontal cortex, but CRF(1) receptor binding also remained unchanged. These results suggest that the therapeutic actions of these mood stabilizers may, in part, result from their actions on central CRF neuronal systems. The distinct actions of each drug on CRF systems may underlie their synergistic clinical effects.

Inhibition of norepinephrine uptake in patients with major depression treated with paroxetine.

OBJECTIVE: The study examined whether paroxetine inhibits the human norepinephrine transporter in addition to the human serotonin (5-HT) transporter in patients with major depressive disorder. METHOD: In an open-label, parallel-group, forced-titration study, 52 outpatients with DSM-IV major depressive disorder and a baseline Montgomery Asberg Depression Rating Scale score > or =20 were randomly assigned to treatment with paroxetine (to 60 mg/day) or desipramine (to 30 mg/day) in a 3-to-1 ratio, respectively. Norepinephrine and 5-HT transporter function were assayed by using human transporter transfected cells in the presence of serum collected at baseline and the end of each treatment week. Data from 36 patients were analyzed. RESULTS: Paroxetine decreased norepinephrine uptake to 73% of control (27% inhibition) at an average serum concentration of 100 ng/ml and 57% of control (43% inhibition) at 200 ng/ml. Uptake of 5-HT was decreased to less than 15% (greater than 85% inhibition) of control at these paroxetine concentrations. Desipramine decreased norepinephrine uptake to near maximal 15% of control (85% inhibition) at 100 ng/ml. Uptake of 5-HT was decreased to 82% of control (18% inhibition) at 100 ng/ml and 49% of control (51% inhibition) at 500 ng/ml. CONCLUSIONS: Paroxetine, currently classified as a selective 5-HT reuptake inhibitor, can act as a 5-HT/norepinephrine uptake inhibitor in vivo. The clinical significance of this action on norepinephrine uptake is currently unknown, but this action may contribute to the broad therapeutic efficacy of paroxetine in the treatment of depression, panic disorder, social anxiety disorder, posttraumatic stress disorder, and generalized anxiety disorder.

Loss of basal forebrain P75(NTR) immunoreactivity in subjects with mild cognitive impairment and Alzheimer's disease.

The long-held belief that degeneration of the cholinergic basal forebrain was central to Alzheimer's disease (AD) pathogenesis and occurred early in the disease process has been questioned recently. In this regard, changes in some cholinergic basal forebrain (CBF) markers (e.g. the high affinity trkA receptor) but not others (e.g., cortical choline acetyltransferase [ChAT] activity, the number of ChAT and vesicular acetylcholine transporter-immunoreactive neurons) suggest specific phenotypic changes, but not frank neuronal degeneration, early in the disease process. The present study examined the expression of the low affinity p75 neurotrophin receptor (p75(NTR)), an excellent marker of CBF neurons, in postmortem tissue derived from clinically well-characterized individuals who have been classified as having no cognitive impairment (NCI), mild cognitive impairment (MCI), and mild AD. Relative to NCI individuals, a significant and similar reduction in the number of nucleus basalis p75(NTR)-immunoreactive neurons was seen in individuals with MCI (38%) and mild AD (43%). The number of p75(NTR)-immunoreactive nucleus basalis neurons was significantly correlated with performance on the Mini-Mental State Exam, a Global Cognitive Test score, as well as some individual tests of working memory and attention. These data, together with previous reports, support the concept that phenotypic changes, but not frank neuronal degeneration, occur early in cognitive decline. Although there was no difference in p75(NTR) CBF cell reduction between MCI and AD, it remains to be determined whether these findings lend support to the hypothesis that MCI is a prodromal stage of AD.