Venlafaxine monitoring

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... 

Patients given venlafaxine should have blood pressure monitored regularly. 

Venlafaxine (Effexor, Effexor XR). Venlafaxine, a dual serotonin-norepinephrine reuptake inhibitor, has only recently been used to treat ADHD with a few case reports suggesting it may provide modest benefit for both inattention and impulsivity. Effexor XR is generally well tolerated, though it can elevate blood pressure somewhat at higher doses. This should be monitored especially when venlafaxine is coadministered with a stimulant. Controlled trials are needed. 

Sustained hypertension There is a dose-dependent increase in the incidence of sustained hypertension for venlafaxine from 3% for doses less than 100 mg/day up to 13% for doses greater than 300 mg/day. It is recommended that patients receiving venlafaxine have regular monitoring of blood pressure. For patients who experience a sustained increase in food pressure, consider dose reduction or discontinuation. Renal/Hepatic function impairment In patients with renal impairment (GFR, 10 to 70 mL/min) or cirrhosis of the liver, a lower dose may be necessary. 

C. Nortriptyline (Pamelor) is a TCA, and as a class these drugs require at least one steady-state blood level to safely and effectively use the medication. Paroxetine, venlafaxine, and bupropion have not had blood levels correlated to response, and their relatively low toxicity does not require therapeutic blood monitoring. Nardil is a MAOI, which can be... 

Grunder G, Wetzel H, Schloer R, et al. Subchronic antidepressant treatment with venlafaxine or imipramine and effects on blood pressure assessment by automatic 24 hour monitoring. Pharmacopsychiatry 1993 26 155. 

A 44-year-old woman took an overdose of venlafaxine 3 g. An electrocardiogram showed sinus rhythm and incomplete right bundle branch block (32). She was monitored in an intensive care unit and 10 hours later a further electrocardiogram showed atrial fibrillation with a wide QRS complex. Both of these abnormalities resolved with sodium bicarbonate (100 ml of a 1 M solution). No further conduction disturbances were noted over the following days. 

The authors suggested that the effect of venlafaxine on cardiac conduction is mediated by its ability to block the fast inward sodium current in cardiac myocytes. This might promote membrane stabilizing effects in a similar way to tricyclic antidepressants. They recommended that the management of venlafaxine overdose should include cardiac monitoring. 

A 47-year-old man with a long history of depression had been stable on a combination of venlafaxine 300 mg/day and mirtazapine 30 mg/day for 3 months. He started to take tramadol for a chronic pain syndrome and the dose was titrated up to 300 mg/day over the next 4 weeks. The dose was then increased to 400 mg/day, and 8 days later he developed shivering, sweating, myoclonus, hyper-reflexia, and mydriasis. His medications were withdrawn, but over the next 4 hours he developed a fever (39.2°C) and a tachycardia. He was given intravenous hydration and closely monitored, and the symptoms resolved over the next 36 hours. Venlafaxine and mirtazapine were restarted and he remained symptom free. 

BETA-BLOCKERS VENLAFAXINE T plasma concentrations and efficacy of metoprolol, propranolol and timolol Venlafaxine inhibits CYP2D6-mediated metabolism of metoprolol, propanolol and timolol Monitor PR and BP at least weekly watch for metoprolol toxicity (in particular, toss of its cardioselectivity) and propanolol toxicity... 

LITHIUM OTHER-VENLAFAXINE Possible risk of serotonin syndrome Additive effect Be aware of the possibility of serotonin syndrome. Also need to monitor lithium levels with appropriate dose adjustments during co-administration >- For signs and symptoms of serotonin toxicity, see Clinical Features of Some Adverse Drug Interactions, Serotonin toxicity and serotonin syndrome... 

SSRIs METOPROLOL t plasma concentrations of metoprolol SSRIs inhibit metabolism of metoprolol (paroxetine, fluoxetine, sertraline, fluvoxetine, and venlafaxine via CYP2D6 (es)citalopram uncertain at present) Monitor PR and BP closely watch for metoprolol toxicity, in particular loss of its cardioselectivity... 

Venlafaxine produces some unwanted effects that resemble those of SSRIs with a higher incidence of nausea. Sustained hypertension (due to blockade of noradrenaline reuptake) is a problem in a small percentage of patients at high dose and blood pressure should be monitored when > 200 mg/day is taken. 

Patients should receive a 2-3 month initial course of treatment, with close monitoring for improvement in PTSD symptoms such as reexperiencing (flashbacks, nightmares), hyperarousal (insomnia and startle responses) and avoidance (30). Patients showing no improvement after 8 weeks of maximal doses are candidates for treatment with a different SSRI or with either venlafaxine or mirtazapine (30). Those with partial responses may need more time to respond to the first line SSRI (30). 

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. ... 

Figure 3.12 Plot of SRM data points collected every 10 ms using Turbo IonSpray (TIS) and the ESI Chip for venlafaxine (SRM mjz 278.2 > mjz 58.1). A 5 pM venlafaxine solution at 5 pLmin-1 was mixed with 400 pL min-1 of 75% acetonitrile, 25% water and 0.2% formic acid. This solution was sprayed using TIS at 450 °C while monitoring the venlafaxine SRM from mjz 278.2 to mjz 58.1. A 5pM venlafaxine solution at 5pLmin 1 was mixed with 600 pL min 1 of 75% acetonitrile, 25% water and 0.2% formic acid. This solution was split to deliver 200 nLmin-1 to the ESI Chip while monitoring the venlafaxine SRM from mjz 278.2 to mjz 58.1. Data collected every 10ms result in a 15% RSD with TIS and 3.4% RSD with the ESI Chip.

Antidepressant drugs A major class of psychotropic drugs with diverse chemical configurations including the monoamine oxidase inhibitors (MAOIs), the heterocyclic drugs (composed of mono-, di-, tri-, and hetero-cyclics), the serotonin reuptake inhibitors (fluoxetine, paroxetine, sertraline, trazodone, and venlafaxine), and bupropion are more recent innovations. Antidepressants usually must be taken for several weeks to have the desired effect and they often have a low therapeutic index, so they must be closely monitored. 

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