Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The chemistry, pharmacology, pharmacokinetics, and clinical efficacy of nefazodone hydrochloride, a new antidepressant, are described. Nefazodone enhances serotonin (5-hydroxytryptamine [5-HT]) synaptic transmission by acting as an antagonist at 5-HT2 receptors and by inhibiting the reuptake of 5-HT. These two mechanisms combined may enhance 5-HT1A-mediated transmission. In addition, nefazodone weakly inhibits the reuptake of norepinephrine. Nefazodone is a structural analogue of trazodone but is pharmacologically distinct. In placebo-controlled trials, nefazodone was as effective as imipramine for the treatment of major depression and produced clinical benefits in patients with depression-related anxiety and sleep disturbances. More than 2000 patients have received nefazodone in clinical trials. The most commonly reported adverse drug reactions (ADRs) are asthenia, somnolence, dry mouth, nausea, constipation, dizziness, lightheadedness, confusion, abnormal vision, and blurred vision. The incidence of sexual-dysfunction ADRs may be less than that reported for other antidepressants. Nefazodone does not inhibit rapid-eye movement sleep. Nefazodone, an inhibitor of the hepatic P-450 isoenzyme CYP3A4, may increase concentrations of drugs metabolized by this isoenzyme, such as terfenadine, astemizole, triazolam, alprazolam, and midazolam. Caution should be exercised in administering nefazodone hydrochloride with triazolobenzodiazepines, and coadministration with terfenadine or astemizole is contra-indicated. The dosage should start at 100 mg twice daily and then be increased, depending on occurrence of ADRs and the patient's clinical response, to 300-600 mg daily. In elderly or debilitated patients, the initial dosage should be half the usual dosage. Nefazodone hydrochloride is as effective as other available antidepressants and may cause fewer ADRs.
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PMID:Nefazodone: a new antidepressant. 889 78

Depression is a significant problem in the elderly. Because of aging-related pharmacokinetic and pharmacodynamic changes, it is not possible to automatically extrapolate findings on the efficacy or tolerability of antidepressants from younger to older populations. Venlafaxine inhibits both noradrenaline (norepinephrine) and serotonin (5-hydroxytryptamine; 5-HT) reuptake. Analysis of data from phase II and III trials showed that venlafaxine was comparably effective in the young and in a subset of over 350 elderly patients. Venlafaxine dosage needs to be lowered in the elderly with renal impairment. As a weak cytochrome P450 (CYP) inhibitor, it is unlikely to have clinically significant drug interactions. Venlafaxine may be associated with some increase in supine diastolic blood pressure, especially at dosages above 150 mg/day. Nefazodone is a serotonin uptake inhibitor and serotonin 5-HT2A receptor antagonist. Pooled analysis of about 250 patients found nefazodone to be effective in elderly individuals with moderate or severe depressive symptoms, with or without melancholia, in both primary and recurrent episodes. Nefazodone clearance is reduced in patients with hepatic impairment, and plasma concentrations have been reported to be higher in the elderly. Nefazodone is an inhibitor of the CYP3A4 family. There does not appear to be any increase in the frequency or severity of adverse effects in the elderly. Moclobemide is a selective inhibitor of monoamine oxidase type A. Studies in the elderly have found it to be well tolerated and meta-analysis has shown it to be comparably effective in young and elderly populations, and comparable to other antidepressants in terms of efficacy. Neither age nor renal impairment necessitate dosage adjustment, but hepatic impairment does necessitate dosage reduction. Dietary restrictions are not required. Overall, there is a relative paucity of data on the tolerability and efficacy of newer antidepressants in the elderly, especially those with concomitant medical disorders. Data that are available indicate that venlafaxine, nefazodone and moclobemide have comparable efficacy in older and younger patients.
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PMID:Antidepressant use in the elderly. Current status of nefazodone, venlafaxine and moclobemide. 925 75

Mirtazapine is the first of a new class of antidepressants, the noradrenergic and specific serotonergic antidepressants (NaSSA). Its antidepressant effect appears to be related to its dual enhancement of central noradrenergic and serotonin 5-HT1 receptor-mediated serotonergic neurotransmission. Mirtazapine possesses a number of useful pharmacokinetic characteristics such as good absorption, linear pharmacokinetics over the recommended dosage range (15 to 80 mg/day), and an elimination half-life of 20 to 40 hours, thereby allowing once-daily administration. However, since the drug is extensively metabolised by the hepatic cytochrome P450 (CYP) system and is excreted mainly in the urine, its clearance may be reduced by hepatic or renal impairment. In vitro data suggest that from a clinical point of view it is unlikely that mirtazapine would inhibit the metabolism of coadministered drugs metabolised by CYP1A2, CYP2D6 or CYP3A4. In vivo data from a study in extensive and poor metabolisers of debrisoquine indicate that strong inhibitors of CYP2D6 would have no effect on the concentration of racemic mirtazapine. In some placebo-controlled studies mirtazapine showed an early onset of antidepressant action, with significant reductions in total Hamilton Depression Rating Scale and Montgomery-Asberg Depression Rating Scale scores (relative to placebo) noted as early as 1 week after starting treatment. This therapeutic advantage was subsequently maintained during treatment, with mirtazapine proving significantly superior to placebo at treatment end-point in the majority of studies. In comparative trials, the antidepressant efficacy of mirtazapine was comparable with that of tricyclic antidepressants such as amitriptyline, clomipramine and doxepin, and in 2 studies superior to that of trazodone and fluoxetine. Mirtazapine appears to have a broad spectrum of activity, reflected in its efficacy in a variety of clinical settings. Its additional beneficial effects on the symptoms of anxiety and sleep disturbance associated with depression may reduce the need for concomitant anxiolytic and hypnotic medication seen with some antidepressants. Mirtazapine has demonstrated superior tolerability to the tricyclic antidepressants and trazodone, primarily on account of its relative absence of anticholinergic, adrenergic and serotonin-related adverse effects, in particular gastrointestinal adverse effects and sexual dysfunction. It appears that increased sedation associated with the drug is related to subtherapeutic dosages, and that it is reported in substantially fewer patients when the drug is used in appropriate dosages (> or = 15 mg as a single evening dose) from the beginning of treatment. Although 2 cases of reversible severe symptomatic neutropenia have been reported in clinical trials, there have been no additional reports of symptomatic neutropenia since the introduction of this drug to various countries in September 1994. Currently available data and initial clinical experience suggest that with its combination of dual action, simple pharmacokinetics, and clinical efficacy and tolerability, mirtazapine appears to be an important advance in the pharmacotherapy of depression.
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PMID:A risk-benefit assessment of mirtazapine in the treatment of depression. 935 61

Tacrolimus (FK-506) is an important immunosuppressive agent most often given for maintenance immunosuppression to prevent acute cellular organ rejection. A 57-year-old woman with end-stage renal disease presumed secondary to chronic glomerulonephritis underwent a living related renal allograft transplantation. She tolerated the surgery well and was discharged on postoperative day 5. She was stabilized with prednisone, azathioprine, and tacrolimus. Two years after transplantation, nefazodone 50 mg twice/day orally was prescribed due to depression. After 1 week of nefazodone therapy the patient experienced headache, confusion, and "gray areas" in her vision, without abnormal ophthalmologic findings. Her serum creatinine was elevated to 2.2 mg/dl (baseline 1.5 mg/dl), and trough tacrolimus level was markedly elevated (> 30 ng/ml). Both tacrolimus and nefazodone are metabolized by the cytochrome P450 (CYP) 3A4 system. We suspect that nefazodone inhibits metabolism of tacrolimus. Coadministration of antidepressant agents such as nefazodone, or any other drug that inhibits the CYP3A4 isoenzyme subfamily, should be anticipated to interfere with tacrolimus metabolism. Monitoring blood concentrations of tacrolimus is vital, and appropriate dosage adjustments are required when the two drugs are administered concurrently to avoid serious interactions such as nephrotoxicity and neurotoxicity.
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PMID:Interaction between tacrolimus and nefazodone in a stable renal transplant recipient. 985 39

St. John's wort (Hypericum perforatum) is an herbal remedy used widely for the treatment of depression. Recent clinical studies demonstrate that hypericum extracts increase the metabolism of various drugs, including combined oral contraceptives, cyclosporin, and indinavir. In this report, we show that hyperforin, a constituent of St. John's wort with antidepressant activity, is a potent ligand (K(i) = 27 nM) for the pregnane X receptor, an orphan nuclear receptor that regulates expression of the cytochrome P450 (CYP) 3A4 monooxygenase. Treatment of primary human hepatocytes with hypericum extracts or hyperforin results in a marked induction of CYP3A4 expression. Because CYP3A4 is involved in the oxidative metabolism of >50% of all drugs, our findings provide a molecular mechanism for the interaction of St. John's wort with drugs and suggest that hypericum extracts are likely to interact with many more drugs than previously had been realized.
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PMID:St. John's wort induces hepatic drug metabolism through activation of the pregnane X receptor. 1085 61

Commercially available St. John's wort (Hypericum perforatum) extracts, preparations that are used in the treatment of depression, were examined for the potential to inhibit human cytochrome P450 (CYP) enzyme activities, specifically CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. Crude extracts demonstrated inhibition of each of these five enzymes, with CYP2D6, CYP2C9, and CYP3A4 being more sensitive than CYP1A2 and CYP2C19. Extracts were fractionated by HPLC, and each of the fractions was tested for inhibition of these five CYPs to identify individual constituents with inhibitory activity. Several fractions were shown to possess inhibitory activity, including the fractions containing hyperforin (the putative active antidepressant constituent), I3,II8-biapigenin, and hypericin. Hyperforin and I3,II8-biapigenin were isolated from the extract, and inhibition constants for the five CYP activities were measured. In addition, three other constituents, hypericin, quercetin, and chlorogenic acid, were tested for inhibitory activity toward the CYP enzymes. The flavonoid compound I3,II8-biapigenin was shown to be a potent, competitive inhibitor of CYP3A4, CYP2C9, and CYP1A2 activities with K(i) values of 0.038, 0.32, and 0.95 microM, respectively. Hyperforin was a potent noncompetitive inhibitor of CYP2D6 activity (K(i) = 1.5 microM) and competitive inhibitor of CYP2C9 and CYP3A4 activities (K(i) = 1.8 and 0.48 microM, respectively). Hypericin also demonstrated potent inhibition of several CYP activities. These in vitro data indicate that St. John's wort preparations contain constituents that can potently inhibit the activities of major human drug-metabolizing enzymes and suggest that these preparations should be examined for potential pharmacokinetic drug interactions in vivo.
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PMID:Inhibition of human cytochrome P450 enzymes by constituents of St. John's Wort, an herbal preparation used in the treatment of depression. 1087 Dec 99

Improving outcomes for patients with depression involves selecting the best possible drug therapy. Considerations relevant to drug product selection include: 1) pharmacokinetic issues such as half-life and time to steady-state, and protein binding; 2) pharmacodynamic drug-drug interactions; and 3) drug metabolism-related drug interactions. A comparison of selected antidepressants with an emphasis on venlafaxine's similarities and differences is presented. Based on these parameters, selecting an antidepressant medication, such as venlafaxine, that has a low potential for drug interactions at the Cytochrome P450 (CYP) enzyme system, and is easy to monitor and dose, facilitate successful treatment of patients. Venlafaxine has been evaluated in clinical studies that demonstrate low to negligible drug interaction potential at CYP2D6, CYP1A2, CYP2C19, and CYP3A4. Its short half-life and time to steady-state, when coupled with the extended release characteristics of the preferred dosage formulation allow for once daily dosing and rapid attainment of therapeutic effects. The CYP3A4 system is involved in both first-pass metabolism and systemic clearance of medications. Drug interactions at this isoenzyme have proven to be of high clinical relevance ranging from cardiovascular toxicity and death with commonly used drugs such as cisapride, to subtherapeutic levels of cyclosporine or protease inhibitors leading to transplant rejection or HIV relapse. Reasons for the under detection and reporting of drug interaction mediated adverse events include healthcare system structure, the poor return to follow up of non-adherent patients, the need for greater education and training of clinicians to recognize drug-related adverse events, and the reluctance of patients to spontaneously communicate about the unpleasant effects of their medication.
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PMID:Review of the pharmacokinetics, pharmacogenetics, and drug interaction potential of antidepressants: focus on venlafaxine. 1109 12

Ciprofloxacin, given to a patient successfully treated with methadone for more than 6 years, caused profound sedation, confusion, and respiratory depression. We suggest that this was caused by ciprofloxacin inhibition of CYP1A2 and CYP3A4 activity, two of the cytochrome p450 isozymes involved in the metabolism of methadone.
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PMID:Methadone, ciprofloxacin, and adverse drug reactions. 1114 98

Reboxetine is a novel selective norepinephrine inhibitor that has been evaluated in the treatment of patients with depression. Reboxetine is a racemic mixture, and the (S,S)-(+)-enantiomer appears to be the more potent inhibitor. However, the ratio of the areas under the concentration-time curves of the (S,S)-(+)- and (R,R)-(-)-enantiomers in vivo is approximately 0.5. There is no evidence for chiral inversion. Differences in the clearances of the 2 enantiomers may be explained by differences in protein binding. The pharmacokinetics of reboxetine are linear following both single and multiple oral doses up to a dosage of 12 mg/day. The plasma concentration-time profile following oral administration is best described by a 1-compartment model, and the mean half-life (approximately 12 hours) is consistent with the recommendation to administer the drug twice daily. Reboxetine is well absorbed after oral administration. The absolute bioavailability is 94.5%, and maximal concentrations are generally achieved within 2 to 4 hours. Food affects the rate, but not the extent, of absorption. The distribution of reboxetine appears to be limited to a fraction of the total body water due to its extensive (>97%) binding to plasma proteins. The primary route of reboxetine elimination appears to be through hepatic metabolism. Less than 10% of the dose is cleared renally. A number of metabolites formed through hepatic oxidation have been identified, but reboxetine is the major circulating species in plasma. In vitro studies show that reboxetine is predominantly metabolised by cytochrome P450 (CYP) 3A4; CYP2D6 is not involved. Reboxetine plasma concentrations are increased in elderly individuals and in those with hepatic or renal dysfunction, probably because of reduced metabolic clearance. In these populations, reboxetine should be used with caution, and a dosage reduction is indicated. Ketoconazole decreases the clearance of reboxetine, so that the dosage of reboxetine may need to be reduced when potent inhibitors of CYP3A4 are coadministered. Quinidine does not affect the in vivo clearance of reboxetine, confirming the lack of involvement of CYP2D6. There is no pharmacokinetic interaction between reboxetine and lorazepam or fluoxetine. Reboxetine at therapeutic concentrations has no effect on the in vitro activity of CYP1A2, 2C9, 2D6, 2E1 or 3A4. The lack of effect of reboxetine on CYP2D6 and CYP3A4 was confirmed by the lack of effect on the metabolism of dextromethorphan and alprazolam in healthy volunteers. Thus, reboxetine is not likely to affect the clearance of other drugs metabolised by CYP isozymes.
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PMID:Clinical pharmacokinetics of reboxetine, a selective norepinephrine reuptake inhibitor for the treatment of patients with depression. 1119 74

The novel antidepressant mirtazapine has a dual mode of action. It is a noradrenergic and specific serotonergic antidepressant (NaSSA) that acts by antagonizing the adrenergic alpha2-autoreceptors and alpha2-heteroreceptors as well as by blocking 5-HT2 and 5-HT3 receptors. It enhances, therefore, the release of norepinephrine and 5-HT1A-mediated serotonergic transmission. This dual mode of action may conceivably be responsible for mirtazapine's rapid onset of action. Mirtazapine is extensively metabolized in the liver. The cytochrome (CYP) P450 isoenzymes CYP1A2, CYP2D6, and CYP3A4 are mainly responsible for its metabolism. Using once daily dosing, steady-state concentrations are reached after 4 days in adults and 6 days in the elderly. In vitro studies suggest that mirtazapine is unlikely to cause clinically significant drug-drug interactions. Dry mouth, sedation, and increases in appetite and body weight are the most common adverse effects. In contrast to selective serotonin reuptake inhibitors (SSRIs), mirtazapine has no sexual side effects. The antidepressant efficacy of mirtazapine was established in several placebo-controlled trials. In major depression, its efficacy is comparable to that of amitriptyline, clomipramine, doxepin, fluoxetine, paroxetine, citalopram, or venlafaxine. Mirtazapine also appears to be useful in patients suffering from depression comorbid with anxiety symptoms and sleep disturbance. It seems to be safe and effective during long-term use.
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PMID:A review of the pharmacological and clinical profile of mirtazapine. 1160 47


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