Venlafaxine dosage

The effects of buspirone are decreased when the drug is administered with fluoxetine Increased serum levels of buspirone occur if the drug is taken with erythromycin or itraconazole Should any of these combinations be required, the dosage of buspirone is decreased to 2.5 mg BID, and the patient is monitored closely. Venlafaxine blood levels increase with a risk of toxicity when administered witii MAOIs or cimetidine There is an increased risk of toxicity when trazodone is administered with the phenothiazines and decreased effectiveness of trazodone when it is administered with carbamazepine Increased serum digoxin levels have occurred when digoxin is administered with trazodone There is a risk for increased phenytoin levels when phenytoin is administered witii trazodone... 

MISCELLANEOUS ANTIDEPRESSANTS. An uncommon but potentially serious adverse reaction of trazodone is priapism (a persistent erection of die penis). If not treated within a few hours, priapism can result in impotence The nurse instructs the patient to report any prolonged or inappropriate penile erection. Use of the drug is discontinued immediately and the primary care provider notified. Injection of a-adrenergic stimulants (eg, norepinephrine) may be helpful in treating priapism. In some cases, surgical intervention may be required. Venlafaxine may cause an increase in die blood pressure. A sustained increase in die blood pressure may indicate that die dosage of venlafaxine needs to be decreased. 

Venlafaxine may cause a dose-related increase in diastolic blood pressure. Dosage reduction or discontinuation may be necessary if sustained hypertension occurs. Other side effects are similar to those associated with the SSRIs (e.g., nausea and sexual dysfunction). 

These data confirm that venlafaxine, particularly in higher dosages, can significantly increase blood pressure. At high doses, venlafaxine inhibits the re-uptake of noradrenaline as well as that of serotonin, which probably accounts for the pressor effect. 

The most commonly reported adverse effects with venlafaxine include nausea, constipation, somnolence, dry mouth, dizziness, nervousness, sweating, asthenia, abnormal ejaculation/orgasm, and anorexia." These side effects may be dose related. Venlafaxine may cause a dose-related increase in diastolic blood pressure, and basehne blood pressure is not a useful predictor of the occurrence of this phenomenon. Blood pressure should be monitored regularly during venlafaxine therapy, and dosage reduction or discontinuation may be necessary if sustained hypertension occurs. ... 

An adequate trial usually consists of 8 to 12 weeks (at maximum dosages) to confirm efficacy. Subsequent options include a trial of a second SSRI or venlafaxine extended-release. Some patients experience cfinical benefit during the first 4 weeks of therapy. If nonresponsiveness continues, a trial of an alternative agent is warranted. 

Fluvoxamine inhibits liver drug-metabolizing enzymes. Dosages of alprazolam, theophylline, and warfarin must be reduced if any of these drugs are given concomitantly with fluvoxamine. Nefazodone may also decrease the metabolism of benzodiazepines, and venlafaxine may inhibit haloperidol metabolism. The answer is (B). 

Whenever venlafaxine is being discontinued after more than 1 week of therapy, it generally is recommended that the patient be closely monitored and the dosage of the drug be tapered gradually to reduce the risk of withdrawal symptoms. 

The evidence is very limited but be aware that increased haloperidol adverse effects may occur if venlafaxine is also given. It may be necessary to reduce the haloperidol dosage. 

A 69-year-old man with bipolar disorder, who had been taking venlafaxine up to 337.5 mg daily, thioridazine 25 mg at night, and sodium valproate 1.2 g daily for several months with no adverse motor symptoms, experienced extrapyramidal effects 3 to 4 days after the venlafaxine had been gradually replaced by nortriptyline 50 mg daily. Symptoms persisted despite withdrawal of thioridazine, but improved on reduction of the nortriptyline dosage to 20 mg daily. The cause of the reaction was not known, but it was suggested that there may have been an interaction between venlafaxine and nortriptyline possibly modulated by thioridazine or sodium valproate. 

Serotonin-norepinephrine reuptake inhibitors (SNRIs) (e.g. duloxetine, venlafaxine and desvenlafax-ine) inhibit the reuptake of both serotonin and norepinephrine and are referred to as dual inhibitors or selective serotonin norepinephrine inhibitors . The SNRIs lack of anticholinergic side effects results in a distinct advantage over traditional TCAs [13,77,78]. For example, duloxetine is a potent, balanced inhibitor of serotonin and norepinephrine reuptake [79]. Venlafaxine inhibits serotonin reuptake at lower dosages and inhibits both serotonin and norepinephrine reuptake at higher dosages [70,80]. 

Somasekhag V., Gowrisankar, D. and Shivakumar, H. N. Development and validation of a rapid RP-HPLC method for the determination of venlafaxine hydrochloride in pharmaceutical dosage forms using experimental design. E-J. Chem. 6(4) 1091-1102, October 2009. 

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