Clinical implications of the pharmacology of serotonin reuptake inhibitors

Acute and subchronic treatments with selective serotonin reuptake inhibitors increase Nociceptin/Orphanin FQ (NOP) receptor density in the rat dorsal raphe nucleus; interactions between nociceptin/NOP system and serotonin

Nociceptin/Orphanin FQ is the endogenous ligand of NOP receptor, formerly referred to as the Opioid Receptor-Like 1 receptor. We have previously shown that NOP receptors were located on serotonergic neurons in the rat dorsal raphe nucleus, suggesting possible direct interactions between nociceptin and serotonin in this region, which is a target for antidepressant action. In the present study, we investigated further the link between Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant treatments and the nociceptin/NOP receptor system. Intraperitoneal administration of the SSRI citalopram induced an increase in NOP-receptor density, measured by autoradiographic [(3)H] nociceptin binding, in the rat dorsal raphe nucleus, from the first to the 21st day of treatment. This effect was also observed with other SSRIs (sertraline, fluoxetine), but not with two tricyclic antidepressants (imipramine, clomipramine) and was abolished by pre-treatment with para-chlorophenylalanine, an inhibitor of serotonin synthesis. Using microdialysis experiments, we demonstrated that NOP-receptor activation by infusion of nociceptin 10(-6) M or 10(-5) M increased the level of extracellular serotonin in the dorsal raphe nucleus. This effect was abolished by co-infusion of the NOP-receptor antagonist UFP 101. These results confirm the existence of reciprocal interactions between serotonin and nociceptin/NOP transmissions in the dorsal raphe nucleus.

Persistence and dissipation pathways of the antidepressant sertraline in agricultural soils

Sertraline is a widely-used antidepressant that is one of the selective serotonin reuptake inhibitors. It has been detected in biosolids and effluents from sewage treatment plants. Since sertraline can reach agriculture land through the application of municipal biosolids or reclaimed water, the persistence and dissipation pathways of (3)H-sertraline were determined in laboratory incubations using three agriculture soils varying in textures and properties. The total solvent extractable radioactivity decreased in all three soils with times to dissipate 50% of material (DT50) ranging from 48.1±3.5 (loam soil) to 84.5±13.8 (clay soil) days. Two hydroxylated sertraline transformation products were identified in all three soils by high performance liquid chromatography with time-of-flight mass spectrometry (HPLC-TOF-MS), but the accumulation did not exceed 10% of the initial parent concentration. The addition of liquid municipal biosolids to the loam soil had no effect on the rate of sertraline dissipation, or production of transformation products. In summary, sertraline was persistent in agricultural soils with major dissipation pathways including the production of non-extractable soil-bound residues, and accumulation of hydroxylated transformation products. The biologically active sertraline transformation product norsertraline was not detected in soil.

Disinhibition as a side effect of treatment with fluvoxamine in pediatric patients with obsessive-compulsive disorder

Selective serotonin reuptake inhibitors (SSRIs) are usually well tolerated in the pediatric population, and widely used in the treatment of obsessive-compulsive disorder (OCD). Of the 51 pediatric patients with obsessive-compulsive disorder seen in our outpatient clinic between January 2009 and July 2009, 3 of them developed behavioral disinhibition after treatment with fluvoxamine. These cases are described and discussed in relation to the use of CYP2D6 and CYP2C19 pharmacogenetic testing in patients treated with serotonin-selective reuptake inhibitors.

Once-daily duloxetine 60 mg in the treatment of major depressive disorder: multicenter, double-blind, randomized, paroxetine-controlled, non-inferiority trial in China, Korea, Taiwan and Brazil

The aim of the present paper was to compare the efficacy and safety of duloxetine with paroxetine in the acute treatment of major depressive disorder (MDD). In a randomized, double-blind trial of 8 weeks active treatment, patients with non-psychotic MDD were randomized to duloxetine 60 mg (n = 238) or paroxetine 20 mg (n = 240) once daily. Efficacy was primarily measured on change in the 17-item Hamilton Rating Scale for Depression (HAMD(17)) using a non-inferiority test with a margin of 2.2. Secondary efficacy measures included the HAMD(17) subscales, Hamilton Rating Scale for Anxiety, Clinical Global Impressions-Severity, Patient Global Impressions-Improvement, Somatic Symptoms Inventory and Visual Analog Scales (VAS) for pain. Safety measures included treatment-emergent adverse events (TEAE), vital signs, weight, laboratory analyses and electrocardiograms. Non-inferiority of duloxetine to paroxetine was demonstrated because the upper bound of the confidence interval for mean difference in HAMD(17) change (0.71) was less than the non-inferiority margin. Secondary efficacy end-points did not differ significantly between treatments with the exception of VAS back pain, where the pooled mean was lower in the duloxetine group (17.1) compared with the paroxetine group (20.3, P = 0.048). No significant differences were observed in the number of early discontinuations and overall TEAE. However, significantly greater proportions of patients in the duloxetine group experienced nausea and palpitations. No clinically relevant changes in laboratory values, vital signs, weight or electrocardiograms were observed with either treatment. The present study verifies the utility of duloxetine as an efficacious and safe treatment for both emotional and physical symptoms of MDD in this predominantly Asian patient sample.

Direct and indirect interactions between antidepressant drugs and CYP2C6 in the rat liver during long-term treatment

The aim of the present study was to investigate the influence of tricyclic antidepressants (TADs: imipramine, amitriptyline, clomipramine, desipramine), selective serotonin reuptake inhibitors (SSRIs: fluoxetine, sertraline) and novel antidepressant drugs (mirtazapine, nefazodone) on the activity of CYP2C6 measured as a rate of warfarin 7-hydroxylation. The reaction was studied in control liver microsomes in the presence of the antidepressants, as well as in microsomes of rats treated intraperitoneally (i.p.) for one day or two weeks with pharmacological doses of the drugs (imipramine, amitriptyline, clomipramine, nefazodone at 10 mg/kg i.p.; desipramine, fluoxetine, sertraline at 5mg/kg i.p.; mirtazapine at 3mg/kg i.p.), in the absence of the antidepressants in vitro. Some of the investigated antidepressant drugs added to liver microsomes of control rats inhibited the rate of 7-hydroxylation of warfarin. The obtained K(i) values indicated that nefazodone and fluoxetine were the most potent inhibitors of the studied reaction (K(i)=13 and 23microM, respectively), while tricyclic antidepressants and sertraline were weak in this respect (K(i)=70-127microM). A one-day (i.e. 24h) exposure to fluoxetine and mirtazapine resulted in a significant increase in the rate of the 7-hydroxylation of warfarin in rat liver microsomes. The other studied antidepressants did not significantly affect the rate of the CYP2C6-specific reaction. After two-week treatment with the investigated antidepressants, the increase in CYP2C6 activity observed after 24-h exposure to fluoxetine and mirtazapine was more pronounced. Moreover, unlike after one-day exposure, imipramine and sertraline significantly increased the activity of the enzyme. The other tricyclic antidepressants or nefazodone did not produce any significant effect when administered in vivo. The above-described enhancement of CYP2C6 activity correlated positively with the simultaneously observed increases in the enzyme protein level, which indicates the enzyme induction. The studied antidepressants increased the CYP2C6 protein level in the liver microsomes of rats after chronic treatment: imipramine to 174.6+/-18.3%, fluoxetine to 159.1+/-13.7%, sertraline to 135.3+/-11.2% and mirtazapine to 138.4+/-10.2% of the control. In summary, two different mechanisms of the antidepressant-CYP2C6 interaction have been found to operate in the rat liver: 1) direct inhibition of CYP2C6 shown in vitro mainly for nefazodone and fluoxetine, with their inhibitory effects being somewhat more potent than their action on human CYP2C9; 2) the in vivo induction of CYP2C6 by imipramine, fluoxetine, sertraline and mirtazapine.

The effect of tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs) and newer antidepressant drugs on the activity and level of rat CYP3A

The aim of the present study was to investigate the influence of tricyclic antidepressants (TADs: imipramine, amitriptyline, clomipramine, and desipramine), selective serotonin reuptake inhibitors (SSRIs: fluoxetine and sertraline) and novel antidepressant drugs (mirtazapine and nefazodone) on the activity of CYP3A measured as a rate of testosterone 2beta- and 6beta-hydroxylation. The reaction was studied in control liver microsomes in the presence of the antidepressants, as well as in microsomes of rats treated intraperitoneally (i.p.) for 1 day or 2 weeks with pharmacological doses of the drugs (imipramine, amitriptyline, clomipramine, nefazodone 10 mg kg(-1) i.p.; desipramine, fluoxetine, sertraline 5 mg kg(-1) i.p.; mirtazapine 3 mg kg(-1) i.p.), in the absence of the antidepressants in vitro. The investigated antidepressants added to control liver microsomes produced some inhibitory effects on CYP3A activity, which were very weak (most of TADs, K(i)=145-212 microM), modest (clomipramine and sertraline, K(i)=67.5 and 62 microM, respectively) or moderate (nefazodone and fluoxetine, K(i)=42 and 43 microM, respectively). Mirtazapine did not display this kind of properties. One-day exposure of rats to TADs substantially decreased the activity of CYP3A in liver microsomes, which was maintained during chronic treatment. The observed decreases in the enzyme activity were in contrast to the increased CYP3A protein level found after chronic treatment with TADs. On the other hand, sertraline increased the activity of the enzyme after its prolonged administration and its effect correlated positively with the observed elevation in CYP3A protein level. Fluoxetine, mirtazapine and nefazodone did not change the activity of CYP3A in liver microsomes after their administration to rats. Three different mechanisms of the antidepressants-CYP3A interaction are postulated: 1) a direct inhibition of CYP3A by nefazodone, SSRIs and clomipramine, shown in vitro, with the inhibitory effect of nefazodone being the strongest, but weaker than the effects of this drug on human CYP3A4; 2) in vivo inhibition of CYP3A produced by 1 day and maintained during chronic treatment with TADs, which suggests inactivation of the enzyme by reactive metabolites; 3) in vivo induction by sertraline of CYP3A produced only by chronic treatment with the antidepressant, which suggests its influence on the enzyme regulation.

The influence of long-term treatment with psychotropic drugs on cytochrome P450: the involvement of different mechanisms

This paper emphasises that besides the direct action of psychotropic drugs on cytochrome P450 (CYP) (i.e., the binding of the parent drug to the enzyme) indirect mechanisms of CYP-psychotropic interactions, namely the formation of CYP-reactive metabolite complexes and their influence on enzyme regulation, are also very important. The described interactions that are time-, drug- and CYP isoform-dependent may overlap during long-term treatment. The final result of the overlapping depends on the dosage and time interval after the last administration of a drug, which determines the concentration of the parent drug and its metabolites in the environment of the enzyme. These interactions may occur not only in the liver, but also in the brain, and may change the activity of CYP towards the metabolism of drugs, sex steroids, neurosteroids and amine neurotransmitters. The role of the CNS in the regulation of CYP by psychotropics and the significance of CYP-psychotropic interactions for pharmacological and clinical profiling of these drugs is discussed. In addition, different experimental approaches for studying CNS-acting drugs are compared.

Seizures induced by low-dose right unilateral and bifrontal electroconvulsive stimuli

The duration of electroconvulsive therapy (ECT) seizures of depressive patients has been found to be inversely related to titrated right unilateral (RUL) and bilateral (BL) seizure threshold (ST) levels. This inverse relationship is thought to reflect those neural processes determining seizure duration. The relation between seizure duration and titrated ST level in bifrontal (BF) ECT, which has not been previously studied, is examined here in addition to RUL ECT. We found an inverse relationship in RUL ECT but no relationship in BF ECT. Eighteen percent of RUL patients seized at the first stimulus level versus 40% of BF patients. Compared with previous studies, both our starting dose and the increments between stimuli were greater in BF ECT (50.4 mC) than in RUL ECT (25.2 mC). A relationship between stimulus dose and seizure length may have also been present in BF ECT had similar titration schedules been used for both electrode placements. Future studies using titration schedules with a lower initial dose and finer gradations between stimulus levels are needed to evaluate whether a relationship between stimulus dose and seizure duration exists in BF ECT.

Duloxetine: A New Treatment for the Emotional and Physical Symptoms of Depression

BACKGROUND: Depression is underdiagnosed in the primary care setting. Physical symptoms such as aches, pains, and gastrointestinal disturbance are frequently associated with major depressive disorder (MDD) and are often the presenting symptoms. Duloxetine, a dual-reuptake inhibitor of serotonin and norepinephrine, may have a positive effect on physical symptoms in addition to efficacy in treating emotional symptoms of depression. METHOD: Efficacy was evaluated in 6 double-blind, placebo- and/or active comparator-controlled trials of duloxetine for patients with MDD (DSM-IV criteria). Efficacy in depression was determined primarily using the 17-item Hamilton Rating Scale for Depression (HAM-D-17). Secondary efficacy measures included subscales of the HAM-D-17 and assessment of physical symptoms. Safety evaluations included adverse events, vital signs, laboratory analyses, and electrocardiograms. Safety was evaluated by pooling the data from the MDD trials and a study of duloxetine in nondepressed patients. RESULTS: Duloxetine demonstrated significant differences from placebo on core mood symptoms, physical symptoms (e.g., back pain), and global functioning as early as week 1 of treatment. The estimated probabilities of remission in the studies that demonstrated efficacy ranged from 43% to 57%. The most frequently observed adverse events for duloxetine-treated patients included nausea, dizziness, insomnia, fatigue, and somnolence. Duloxetine did not prolong corrected QT intervals, and the rate of sustained elevations of blood pressure did not differ significantly from placebo. CONCLUSION: In these studies, duloxetine was safe and effective in the treatment of both emotional and physical symptoms of MDD. Based on dose assessments, 60 mg q.d. appears to be the optimum starting and therapeutic dose.

A randomised, double-blind comparison of milnacipran and imipramine in the treatment of depression

This multicentre, double-blind, randomised trial in 109 patients compared the efficacy and tolerance of the novel selective serotonin and noradrenaline reuptake inhibitor (SNRI) antidepressant milnacipran (50 mg twice daily, n=53) with the established tricyclic agent imipramine (75 mg twice daily, n=56) over a period of 6 weeks, in patients with major depression (Montgomery-Asberg depression rating score (MADRS) > or =25). Initiation of antidepressant medication was conducted during a 2-week period of hospitalisation, after a 3- to 7-day washout period. Concomitant psychiatric medication was limited to lorazepam, cyamemazine, chloral hydrate and long-term uncomplicated lithium therapy. Assessment for efficacy using the MADRS and Hamilton rating scales of depression, a visual analogue scale and global evaluation revealed both agents to be highly effective (P=0.0001) in this group of patients. Milnacipran was found to be of similar efficacy to imipramine. Tolerance, assessed by physiological and biochemical examinations with routine inventory and spontaneous report of adverse events, revealed a clear advantage for milnacipran. The incidence of anticholinergic events with milnacipran was about half that with imipramine and the overall incidence of adverse events by either reporting method was markedly lower with milnacipran than with imipramine. Furthermore, the patient drop-out rate with imipramine was double that experienced with milnacipran. Milnacipran appears to possess equal antidepressant efficacy to imipramine but with markedly superior tolerance. Therefore, milnacipran constitutes an important new treatment option in major depression.

Management of anxiety disorders: the added challenge of comorbidity

Patients with anxiety present with a wide variety of disorders that cause significant impairment to their everyday lives. To complicate matters, patients seldom present with just one anxiety disorder. Such comorbidity, particularly where depression is also present, has important implications for both the patient and the physician. The patient typically suffers from a greater degree of everyday impairment, is more reliant on healthcare services, in particular mental health services, and may be at a greater risk of attempting suicide. For the physician, comorbidity in anxiety disorders presents a challenge as the patient's symptoms are often more severe, present earlier in life, and are frequently prolonged which makes their management more complex. This review will focus on the anxiety disorders: panic disorder, obsessive-compulsive disorder, social anxiety disorder, and post-traumatic stress disorder. The impact of co-existing multiple anxiety disorders, depression, or a history of substance abuse will be discussed with a view to choosing the appropriate management strategy. Treatment options will be reviewed.

A reference guide to drugs and dry mouth--2nd edition

Xerostomia (dry mouth) is an uncomfortable and potentially harmful oral symptom which is usually caused by a decrease in the secretion rate of saliva (salivary gland hypofunction, or SGH). It is more prevalent in the elderly population, primarily due to their increased use of drugs and their susceptibility to disease. Many drugs and drug classes have been linked to xerostomia; the xerogenic effect increases when many drugs are taken concurrently. This Reference Guide to Drugs and Dry Mouth is designed to allow the reader to rapidly identify those pharmacologic agents which have the capacity to induce xerostomia and SGH. Xerogenic drugs can be found in 42 drug categories and 56 sub-categories. A guide to the management of drug-induced SGH and xerostomia is also provided.

Pharmacology of the selective serotonin reuptake inhibitors in children and adolescents

OBJECTIVE

To review the pharmacology of a new class of medications, the potent selective serotonin reuptake inhibitors (SSRIs), what is known about their metabolism in children and adolescents, and the practical clinical implications of such.

METHOD

Articles were retrieved through index Medicus searches for articles published during the past 10 years on the SSRIs and on pediatric pharmacology.

RESULTS

More than 300 articles were reviewed. Pharmacological data, derived from relevant adult literature, were summarized and extrapolated to children and from the limited pediatric literature. The SSRIs represent a new class of antidepressants with distinct advantages in their side effect profile and their broad therapeutic index over that seen with the tricyclic antidepressants. Their advantage of few anticholinergic side effects and limited cardiovascular toxicities are particularly relevant for the pediatric population. The SSRIs are metabolized via the hepatic cytochrome isoenzyme P450 system, and potential drug-drug interactions are reviewed.

CONCLUSIONS

The SSRIs appear to offer advantages over the tricyclic antidepressants. Unfortunately, pharmacokinetic data are lacking, and systematic studies of safety and efficacy in the pediatric age group are limited. Preliminary reports are encouraging, but further study is required.

Interactions between different antidepressants and morphine alter gastrointestinal transit in mice

To determine different serotoninergic antidepressants' effects on the gastrointestinal (GI) inhibiting effect induced by morphine, mice were pretreated with mianserin (a tetracyclic antidepressant with multiple 5-HT receptor subtypes interactions) and with fluoxetine (a selective 5-HT reuptake inhibitor). Mianserin alone, produced gastrointestinal inhibition in a dose-dependent manner. Naloxone did not reverse this inhibiting effect, indicating that different mechanism of action are involved in morphine- and mianserin-induced inhibition of the gastrointestinal transit. Fluoxetine injected alone produced an increased propulsive motility of the GI transit. This effect was not reversed by naloxone. Fluoxetine did not reduce significantly mianserin-induced inhibition of GI transit. Fluoxetine also mildly reversed morphine-induced gastrointestinal inhibition, suggesting some degree of involvement of the opiates through the serotoninergic system.

A comparison of augmenting central serotonin and noradrenaline function in healthy subjects: implications for studies on the neurochemistry of anxiety

Biochemical and psychophysiological effects of augmenting serotonergic and noradrenergic function were compared in 12 normal volunteers. Fluvoxamine (100 mg), a serotonin (5-HT) re-uptake inhibitor, maprotiline (75 mg), a noradrenaline re-uptake inhibitor, and placebo were given for 7 days each to each subject. Subjects were tested pre-drug on days 1, 4 and 8 of each treatment. Catecholamines in 24 h urine, 'platelet-rich' plasma 5-HT and hormones, EEG, auditory evoked response, skin conductance, and bodily and psychological responses were monitored. Augmentation of central 5-HT by fluvoxamine was demonstrated by the decrease of 5-HT plasma levels. Fluvoxamine also reduced urinary dopamine, indicating a decrease in dopamine metabolism in response to augmentation of 5-HT function. Decrease in pulse rate, loss of appetite and a mild arousing effect were also detected with administration of fluvoxamine. Thus, further investigations on the neuro chemistry of anxiety disorders should include the study of mechanisms of interaction of neurotransmitters.

The SSRIs: advantages, disadvantages and differences

The highly specific mechanism of action of the selective serotonin re-uptake inhibitors (SSRIs) confers advantages on this group, relative to other classes of antidepressant, and thus represents a significant advance in the pharmacotherapy of depression. Whilst their clinical efficacy is equivalent to that of the tricyclic antidepressants (TCAs), the SSRIs have a greatly reduced risk of toxicity in overdose and have been shown to be significantly better tolerated. Specifically, the SSRIs have a low incidence of anticholinergic effects and are essentially devoid of cardiotoxicity. This tolerability advantage may be of significance in improving compliance and hence cost-effectiveness of treatment, particularly in the long term. Despite a lack of sedative effect, there is evidence that SSRIs are more effective than TCAs in the treatment of depression with anxiety. In addition, the SSRIs have been shown to be effective in obsessive-compulsive disorder, panic disorder and social phobia. Although superior efficacy has not been demonstrated for any one of the SSRIs, the structural diversity of this group is reflected in emerging qualitative and quantitative differences in side effects and drug interaction potential. Many of these differential features reflect important variations in pharmacological and pharmacokinetic profiles, including dosage flexibility, washout times, dose-plasma level proportionality and age-related changes in plasma levels. Fluoxetine, for example, has a considerably longer half-life than other SSRIs and side effects and drug interactions may thus occur for an extended period following discontinuation of treatment. Significant differences in the potential for drug interactions in this group are related to their relative potency for inhibition of important liver drug-metabolising enzymes including CYPIID6, CYPIA2 and CYPIIIA4. Large comparative clinical trials of the different SSRIs have yet to be undertaken; however, the differences that have already become apparent provide important information enabling the physician to choose an SSRI appropriate to the individual patient.

The effects of desipramine and iprindole on levels of enantiomers of fluoxetine in rat brain and urine

The antidepressant fluoxetine (FLU) and its N-demethylated metabolite, norfluoxetine (NFLU), each contains a chiral center. The combination of FLU and desipramine (DMI), another antidepressant, has been reported to be useful in treatment of depression, to dramatically increase plasma levels of DMI and also to produce more rapid beta-adrenergic receptor down-regulation in brain than caused by DMI alone. We have now begun studies on the effects of this drug combination on the levels of FLU and NFLU enantiomers in the rat. In addition, the combination of FLU and iprindole (IPR) was also investigated. Male Sprague-Dawley rats were treated intraperitoneally with either normal saline vehicle, DMI (5 mg/kg/day), (R,S)-FLU (10 mg/kg/day) or DMI (5 mg/kg/day) + (R,S)-FLU (10 mg/kg/day) for 4 days. Following the last treatment, 24 h urine samples were collected. Rats were sacrificed and brains were removed. For the IPR study, rats were pretreated with either saline or IPR-HCl (11.2 mg/kg) and then treated 1 h later with (R,S)-FLU. After 5 h, the rats were sacrificed and brains were removed. Brain and urine samples were analyzed by gas chromatography with electron-capture detection for free (R)-and (S)-FLU and (R)- and (S)-NFLU after extraction and reaction with (-)-(S)-N-(trifluoroacetyl)prolyl chloride. The results from the brains of the rats treated with DMI/FLU indicate that levels of enantiomers of both FLU and NFLU were significantly increased over those seen in the animals receiving (R,S)-FLU alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Dyskinesias following treatment with 5-HT re-uptake inhibitors

Three cases of dyskinesia attributable to selective serotonergic antidepressant drugs are presented. The patients were not on other medication nor had they been in preceding weeks. The movement disorder disappeared on cessation of the drug within a time period corresponding to the expected wash-out for the different preparations. The emergence of dyskinesic symptoms coincided with a significant deterioration in mental state after an initial good response to the particular medication. Considering the apparently selective action of the serotonin re-uptake inhibitors, these cases suggest that movement disorders and psychiatric symptoms are unlikely to be due to single neurotransmitter mechanisms and that a disturbance of the balance between the different systems is a more likely hypothesis.