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the antidepressant effect of venlafaxine is associated with increased neurotransmitter activity of the central nervous system.
Venlafaxine and its main metabolite, O-desmethyl-venlafaxine (EFA), are aspartate potent inhibitors of serotonin and norepinephrine reuptake, and they also inhibit dopamine reuptake by neurons.
Venlafaxine and EFA with single or multiple administration reduce β-adrenergic reactions. They equally effectively influence neurotransmitter reuptake. Venlafaxine does not inhibit MAO activity.
Venlafaxine has no affinity for opiate, benzodiazepine, phencyclidine or N-methyl-d-aspartate (NMDA) receptors, nor does it affect the release of norepinephrine from brain tissue.
Pharmacokinetics Absorption. At least 92% with a single oral dose of venlafaxine is absorbed. After taking venlafaxine extended release capsules Cmax venlafaxine and EFA in blood plasma are achieved between 6.0 ± 1.5 and 8.8 ± 2.2 hours, respectively. The rate of absorption of venlafaxine from sustained release capsules of venlafaxine is slower than its elimination rate. So the real T½ after taking the sustained release capsules of venlafaxine (15 ± 6 hours), it is actually a half-absorption period, instead of the actual half-life (5 ± 2 hours), which is noted after taking the immediate release tablets.
After using equal daily doses of venlafaxine in the form of immediate-release tablets or sustained-release capsules, the effects of both venlafaxine and EFA are similar for the two dosage forms, and the plasma concentration fluctuations were slightly lower after treatment with capsules with prolonged release of venlafaxine. Thus, venlafaxine sustained release capsules provide a slow absorption rate, but the same amount of absorption as immediate release tablets.
Metabolism. Venlafaxine and its metabolites are excreted mainly by the kidneys. About 87% of venlafaxine is excreted in the urine within 48 hours as unchanged venlafaxine, unconjugated EFA, conjugated EFA, or secondary metabolites. T½ venlafaxine and its active metabolite EFA are increased in patients with renal and hepatic insufficiency. Taking sustained-release capsules with food does not affect the absorption of venlafaxine or the subsequent formation of EFA.
The gender and age of the patient do not affect the pharmacokinetics of the drug.
In patients with cirrhosis of the liver T½ venlafaxine was extended by approximately 30% and clearance decreased by approximately 50%, and T½ EFA was extended by approximately 60% and clearance decreased by approximately 30%.
In such patients with T renal failure½ venlafaxine after oral administration was prolonged by approximately 50%, clearance was reduced by approximately 24% (in patients with impaired renal function with a glomerular filtration rate (GFR) of 10–70 ml / min). In patients who were on dialysis, T½ venlafaxine was extended by approximately 180%, clearance decreased by approximately 57%.
Also T½ EFA was prolonged by approximately 40%, despite the fact that clearance was unchanged in patients with renal failure (10–70 ml / min). In patients who were on dialysis, T½ EFA was extended by approximately 142%, clearance decreased by approximately 56%. Such patients need dose adjustment.
- Treatment of major depressive episodes; prevention of major depressive episodes; generalized anxiety disorders (GAD); social anxiety disorders (social phobia).
The capsule is taken with food, swallowing it whole and drinking water. the capsule should not be opened, crushed, chewed, put in water.take 1 time per day at about the same time, morning or evening.
Depression. The recommended dose of Velaxin for treatment of depression is 75 mg 1 time per day. If necessary, after completing 2 weeks, the dose can be increased to 150 mg once a day in order to achieve further clinical improvement. If necessary, the dose can be increased to 225 mg / day for mild forms of depression and up to 375 mg / day for severe forms. Any dose increase should be carried out at 37.5–75 mg every 2 weeks or a longer period, but not less than 4 days later.
When a dose of 75 mg was prescribed, an antidepressant effect was observed after completion of 2 weeks of treatment.
GAD and social phobia. The recommended daily dose for the treatment of patients with special types of anxiety, including sociophobia, is 75 mg once a day. If necessary, to achieve clinical improvement after 2 weeks of treatment, it is possible to increase the dose to 150 mg once a day. If necessary, the dose can be increased to 225 mg once a day. The dose can be increased by 75 mg / day every 2 weeks or a longer period, but not less than 4 days later.
When a dose of 75 mg was prescribed, the onset of anxiolytic action was noted after 1 week of treatment.
Supportive care / relapse prevention. According to the recommendations of specialists, treatment of a patient with an episode of depression should be continued for at least 6 months. For maintenance therapy, as well as for the prevention of relapse or new episodes of depression, usually the same doses are used that were effective in a normal episode of depression. The doctor should regularly, at least 1 time in 3 months, monitor the effectiveness of long-term therapy with Velaxin.
Discontinuation of venlafaxine. To stop treatment with venlafaxine, a gradual dose reduction is recommended: if venlafaxine has been used for more than 6 weeks, a dose reduction of at least 2 weeks is recommended.
The time required to gradually reduce the dose depends on the dose, duration of treatment, as well as on the individual sensitivity of the patient.
Renal or liver failure. In renal failure, when GFR is 30 ml / min, dose adjustment is not required, if 30 ml / min - it is necessary to reduce the total daily dose of venlafaxine by 50%. Hemodialysis patients need to reduce the total daily dose of venlafaxine by 50%. To take the drug, you should wait until the completion of the hemodialysis procedure.
With moderate liver failure, the daily dose of venlafaxine is reduced by 50%. In some cases, a dose reduction of more than 50% is possible.
The elderly. Elderly people should not reduce the dose of the drug solely because of the age of the patient. Treatment should be carried out carefully, by analogy with all other drugs. With individual dose selection, special care should be taken if it is increased.
Supportive / continuous / long-term therapy. In accordance with generally accepted principles, the treatment of the acute phase of severe depression must be continued for several months or a long period. With special types of anxiety, including sociophobia, patients can suffer for a long time, so they need long-term therapy.
Discontinuation of venlafaxine. To stop treatment with venlafaxine, a gradual dose reduction is recommended: if venlafaxine has been used for more than 6 weeks, a dose reduction of at least 2 weeks is recommended.
The time required to gradually reduce the dose depends on the dose and duration of treatment.
Hypersensitivity to any of the components of the drug.
Severe arterial hypertension (blood pressure 180/115 mm RT. Art. And above before starting therapy).
Violation of urination due to insufficient outflow of urine (for example, prostate disease).
Severe hepatic or renal failure.
Concomitant use with irreversible MAO inhibitors is contraindicated because of the risk of serotonin syndrome, which is accompanied by symptoms such as agitation, tremor and hyperthermia.
On the part of the blood and lymphatic system: ecchymoses (hemorrhages in the skin or in the mucous membrane), gastrointestinal bleeding; bleeding from the mucous membranes, lengthening of bleeding time, thrombocytopenia, dysrasia (including agranulocytosis, aplastic anemia, neutropenia, pancytopenia).
From the immune system: anaphylactic reactions.
From the endocrine system: increased levels of prolactin in the blood, inadequate secretion syndrome (SNA ADH).
From the side of metabolism and nutrition: increase in cholesterol in the blood, decrease / increase in body weight, hyponatremia, decreased appetite.
From the psyche: unusual dreams, decreased libido, insomnia, nervous irritability, sedation, confusion, depersonalization, apathy, hallucinations, anxiety arousal, manic reactions, delirium (delirium), suicidal thoughts and suicidal behavior (about cases of suicidal thoughts and suicidal ideation behavior was reported during venlafaxine therapy or immediately after discontinuation of therapy), phobias, speech impairment (including dysarthria), mania, hypomania, bruxism, abnormal orgasms (women), apathy.
From the nervous system: headache, dizziness (vertigo), muscle hypertonicity, tremor, paresthesia, stupor, yawning, myoclonus, imbalance and coordination (ataxia), akathisia, cramps, antipsychotic malignant syndrome, serotonergic syndrome, extrapyramidal reactions (including dystonia and dyskinesia), tardive dyskinesia.
From the side of the organ of vision: impaired accommodation, mydriasis, impaired vision, angle-closure glaucoma.
From the side of the hearing organ and labyrinth disorders: ringing in the ears (tinitus).
From the cardiovascular system: palpitations, tachycardia, lengthening of the Q – T interval, ventricular fibrillation, ventricular tachycardia (including torsades de pointes), hypertension, vasodilation (mainly sensation of heat / hot flashes), orthostatic hypotension, syncope, hypotension, arrhythmia, bleeding.
From the respiratory system: yawning, pulmonary eosinophilia, shortness of breath (dyspnea).
From the digestive tract: nausea, dry mouth, decreased appetite, anorexia, constipation, vomiting, taste disturbance, diarrhea, pancreatitis, dyspepsia, abdominal pain.
On the part of the liver and biliary tract: hepatitis, abnormal liver function indicators.
On the part of the skin and subcutaneous tissues: increased sweating (including night sweats), rash, alopecia, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome, pruritus, urticaria, photosensitivity reactions, papular rash, angioedema, ecchymosis.
From the side of musculoskeletal and connective tissue: rhabdomyolysis, arthralgia, myalgia, muscle cramps.
From the kidneys and urinary tract: impaired urination (mainly difficulty), urinary incontinence (pollakiuria), urinary retention.
From the genitals and mammary glands: pathological ejaculation / orgasm in men, lack of orgasm, erectile dysfunction (impotence), menstrual irregularities associated with increased irregular bleeding (e.g. menorrhagia, metrorrhagia), pathological orgasm in women, galactorrhea, decreased libido.
Common disorders: asthenia (increased fatigue), fever, fever.
Withdrawal syndrome. Discontinuation of venlafaxine treatment (especially sudden) usually leads to withdrawal.Adverse reactions such as dizziness, sensory disturbances (including paresthesias), sleep disturbances (including insomnia and deep sleep), anxiety or fear, nausea and / or vomiting, tremor, headache, and flu-like syndrome were most often observed with abrupt cessation of venlafaxine treatment. , diarrhea, palpitations, sweating, emotional instability. The risk of withdrawal symptoms depends on several factors, including the duration of treatment and dose, as well as the rate of dose reduction. Symptoms usually occur in the first few days after discontinuation of treatment, but there have been several cases of the appearance of such symptoms in patients who accidentally missed a dose of the drug. Typically, these reactions are mild or moderate and disappear within 2 weeks, but in some patients they can be severe and / or prolonged (2-3 months or more). Therefore, upon termination of treatment, it is recommended to gradually reduce the dose of venlafaxine over several weeks or months, depending on the needs of the patient.
Research: increase in blood cholesterol, increase / decrease in body weight, electrocardiographic corrected Q – T prolongation, increase in bleeding time, increase in prolactin level in the blood.
In some cases, especially in elderly patients, arterial hypotension may develop at the beginning of treatment. before starting venlafaxine, hell must be corrected. cases of increased heart rate are known, especially when using venlafaxine in high doses.
Venlafaxine can cause mydriasis. Therefore, it is recommended to carefully monitor the condition of patients with increased intraocular pressure and angle-closure glaucoma.
In some depressed patients treated with antidepressants (including venlafaxine), activation of mania or hypomania is possible. Venlafaxine should be prescribed with caution to patients with a history of mania.
Venlafaxine treatment can cause seizures, so it should be prescribed with caution to patients with a history of seizures. With the development of an attack in any patient, treatment with venlafaxine should be discontinued.
A rash developed in 3% of patients receiving venlafaxine. The patient should be informed of the need to inform the doctor if exanthema, urticaria, or any other allergic reaction develops.
In patients receiving venlafaxine, during a clinical examination there were no signs of drug tolerance, the development of behavior aimed at finding a drug dependence or increasing the dose over time. The doctor should establish careful monitoring of the patient’s health to identify signs of drug abuse, especially in those with a history of such symptoms.
In patients with moderate and severe kidney disease or cirrhosis, the clearance of venlafaxine and its active metabolite decreases, and T½ rises. Therefore, such patients may require a dose reduction. By analogy with other antidepressants, the administration of venlafaxine to such patients requires caution. Before starting treatment, liver / kidney function should be assessed.
During the treatment period with venlafaxine, cases of hyponatremia and / or insufficient ADH elimination syndrome were noted, usually in patients with a decrease in BCC or in dehydrated patients, including elderly patients and patients receiving diuretics. For such patients, certain precautions should be taken.
Abnormal bleeding. Medications that inhibit serotonin uptake can lead to decreased platelet function. The risk of bleeding in the skin or mucous membranes, including digestive tract bleeding, may be increased in patients taking venlafaxine.Venlafaxine should be used with caution in patients prone to bleeding, including patients taking anticoagulants or platelet function inhibitors.
With prolonged treatment, the level of cholesterol in the blood serum should be determined.
The effectiveness and safety of venlafaxine treatment in combination with drugs that reduce body weight have not been determined. Any simultaneous administration of venlafaxine with drugs that reduce body weight is not recommended. The appointment of venlafaxine monotherapy or its combination with other drugs to reduce body weight is not shown.
A small number of patients treated with antidepressants, including venlafaxine, may develop aggression, which requires a dose reduction or discontinuation of treatment. By analogy with any other antidepressants, venlafaxine should be used with caution in patients with aggression.
Risk of suicide / suicidal thoughts or worsening clinical condition. Depression is characterized by an increased risk of suicidal thoughts, self-harm and suicide attempts (suicidal actions). This risk exists until remission is achieved. Since there may be a lack of improvement in the first few weeks or for a long period of time after the start of treatment, patients need to be carefully monitored until their condition improves. General experience with antidepressant medications shows that suicide risk may increase in the early stages of recovery.
Other mental disorders for which venlafaxine is prescribed may also be at increased risk of suicidal actions. In addition, these disorders can be accompanied by a major depressive disorder, therefore the same safety measures should be followed when treating patients with other mental disorders as when treating patients with a major depressive disorder.
Patients with a history of suicidal behavior, as well as patients with a pronounced degree of suicidal ideation, even before starting treatment, have a higher risk of suicidal thoughts or attempted suicide and should be under medical supervision during treatment.
During treatment with venlafaxine, and especially at an early stage of therapy, as well as after changing the dose, careful monitoring of patients and especially patients at risk is necessary. Patients (and also those caring for patients) should be warned about the need to control the deterioration of the clinical condition, the appearance of suicidal actions or thoughts and unusual changes in behavior, and that if such symptoms appear, you should immediately consult a doctor.
Serotonin syndrome. When treated with venlafaxine, especially in combination with other agents, such as MAO inhibitors, which can act on the serotonergic neurotransmitter system, serotonin syndrome can develop - potentially life-threatening.
Symptoms of the serotonin syndrome may include changes in the mental state (e.g. anxiety arousal, hallucinations, coma), disorders of the autonomic nervous system (e.g. tachycardia, unstable blood pressure, hyperthermia), neuromuscular disorders (e.g. hyperreflexia, impaired coordination) and / or gastrointestinal intestinal disorders (e.g. nausea, vomiting, diarrhea).
Akathisia / psychomotor anxiety. The use of venlafaxine is accompanied by the development of akathisia, which is subjectively characterized by unpleasant or anxious anxiety and the need for frequent movement, which is accompanied by an inability to sit or stand still. Most often this occurs in the first few weeks of treatment. In patients who develop such symptoms, increasing the dose can be fatal.
Dry mouth.When treated with venlafaxine, 10% of patients had a dry mouth. This may increase the risk of tooth decay, and patients should be reminded of the importance of dental hygiene.
Angle-closure glaucoma. There are reports of the occurrence of mydriasis in connection with venlafaxine. Therefore, it is recommended that patients with increased intraocular pressure or at risk of developing acute angle-closure glaucoma be closely monitored.
HELL. Venlafaxine, depending on the dose, can increase blood pressure. It is necessary to carefully monitor the parameters of blood pressure in all patients and prior to treatment with venlafaxine, normalize blood pressure, it is recommended to measure it periodically - at the beginning of treatment and after increasing the dose. Caution is advised in patients in whom the underlying disease could have been caused by an increase in blood pressure, for example, in persons with impaired cardiac function. Perhaps the development of postural hypertension, so patients, especially the elderly, need to be warned about possible dizziness, impaired motor coordination.
Heart rate. Heart rate may increase, especially when using the drug in high doses. Patients whose general condition may depend on heart rate should be careful.
Heart disease and the risk of arrhythmias. The use of venlafaxine has not been studied in patients who have recently had myocardial infarction or with decompensated heart failure. Therefore, in these patients, venlafaxine should be used with caution.
Before prescribing venlafaxine in patients at high risk of severe cardiac arrhythmias, the risk / benefit ratio must be weighed.
Caution should be used in patients with diseases of the cardiovascular system due to the risk of ventricular arrhythmias. On the ECG, there may be changes in the intervals P – R, Q – Tc.
Cramps. Convulsions are possible during venlafaxine therapy. Venlafaxine should be used with caution in patients with a history of seizures. Such patients require careful monitoring. With the development of seizures, treatment should be discontinued.
Cholesterol in plasma. With prolonged treatment with venlafaxine, it is necessary to measure the level of cholesterol in the blood serum.
Mania / hypomania. Patients with mood disorders who use antidepressants, including venlafaxine, may develop mania or hypomania. Like other antidepressants, venlafaxine should be prescribed with caution to individuals with a bipolar disorder in a family history.
In clinical studies, it is not proven that patients using venlafaxine develop drug dependence, resistance to therapy, or there is a need to increase the dose.
Aggression. Patients receiving antidepressants, including venlafaxine, may develop aggression. This was reported at the beginning of treatment, after a dose change and upon termination of therapy. Like other antidepressants, venlafaxine should be prescribed with caution to patients with a history of aggression.
Discontinuation of treatment. With the cessation of treatment, withdrawal symptoms usually occur, especially with a sharp cessation of therapy.
The risk of withdrawal symptoms may depend on several factors, including duration of treatment and dose, and rate of dose reduction. Dizziness, sensory disturbances (including paresthesias), sleep disturbances (including insomnia and deep sleep), agitation or anxiety, nausea and / or vomiting, tremor and headache are the most common withdrawal reactions reported. Mostly these symptoms are mild or moderate; however, in some patients, they may be severe. Symptoms usually occur in the first few days after discontinuation of treatment, but there have been several cases of the appearance of such symptoms in patients who accidentally missed a dose of the drug.Typically, these symptoms disappear without treatment within 2 weeks, although in some patients they may be present longer (2-3 months or more). Therefore, upon termination of treatment, it is recommended to gradually reduce the dose of venlafaxine over several weeks or months, depending on the needs of the patient.
Diabetes. Venlafaxine may change the glycemic level, which may require changes in the dosage of antidiabetic drugs and / or insulin.
Laboratory tests of drug interactions. Among patients taking venlafaxine, cases of false-positive results of immunological screening of urine for phencyclidine and amphetamine were recorded. The reason for this may be the lack of a screening test strategy. False positive results may occur within a few days after cessation of venlafaxine treatment. Using confirmatory assays such as gas chromatography / mass spectrometry, venlafaxine can be distinguished from phencyclidine and amphetamine.
Use during pregnancy and lactation
Pregnancy. Studies on the use of venlafaxine in pregnant women have not been conducted. Studies of the effect on reproductive activity in animals are insufficient. The potential risk to humans is unknown. Venlafaxine increases the risk of persistent pulmonary hypertension in newborns. In the case of the use of venlafaxine by the mother before the birth in a newborn, the development of a drug withdrawal syndrome is possible. The use of venlafaxine in pregnant women is contraindicated.
Lactation. Venlafaxine and its metabolite EFA penetrate into breast milk in significant quantities, which can cause severe adverse reactions in the infant; therefore, the use of venlafaxine during lactation is contraindicated. If it is necessary to use the drug, breast-feeding should be discontinued.
Children. The safety and effectiveness of the drug in children have not been studied, therefore, the drug is not used in this age category of patients.
The ability to influence the reaction rate when driving vehicles or working with other mechanisms. When using the drug should refrain from driving vehicles or working with mechanisms.
Irreversible non-selective MAO inhibitors. Venlafaxine should not be used in combination with irreversible non-selective MAO inhibitors. Venlafaxine can be started no earlier than 14 days after the end of therapy with irreversible non-selective MAO inhibitors. After discontinuation of venlafaxine, wait at least 7 days before starting therapy with irreversible non-selective MAO inhibitors.
Reversible selective MAO-A inhibitors (moclobemide). Due to the risk of developing serotonin syndrome, the combination of venlafaxine with reversible selective MAO inhibitors such as moclobemide is contraindicated. Venlafaxine can be started no earlier than 14 days after the end of therapy with reversible MAO inhibitors. After discontinuation of venlafaxine, wait at least 7 days before starting treatment with reversible MAO inhibitors.
Reversible non-selective MAO inhibitors (linezolid). The simultaneous use of the antibiotic linezolid (a weak reversible non-selective MAO inhibitor) with venlafaxine is contraindicated.
Severe adverse reactions have been reported in patients recently discontinuing treatment with MAO inhibitors and initiating venlafaxine therapy or discontinuing treatment with venlafaxine shortly before the start of taking MAO inhibitors. These reactions included tremor, myoclonus, increased sweating, nausea, vomiting, hyperemia, dizziness and hyperthermia with symptoms similar to malignant antipsychotic syndrome, convulsions and death.
In the treatment with venlafaxine, serotonin syndrome can develop, in particular when combined with drugs that affect the serotonergic neurotransmitter system (including triptans, selective serotonin reuptake inhibitors (SSRIs), selective serotonin and noradrenaline reuptake inhibitors (SSRIs, LIOSIS,) tramadol, drugs of Hypericum perforatum (Hypericum perforatum)), with drugs that disrupt the metabolism of serotonin (including MAO inhibitors), or with a precursor erotonin nicknames (e.g. tryptophan supplements). Symptoms of serotonin syndrome include changes in mental status, autonomic lability, neuromuscular disturbances and / or gastrointestinal symptoms.
If the combined use of venlafaxine and SSRIs, SSRIs or a serotonin receptor antagonist (tryptophan) is clinically determined, careful monitoring of patients is recommended, especially at the beginning of treatment and when the dose is increased. The concomitant use of venlafaxine with serotonin precursors (such as tryptophan) is not recommended.
Drugs that affect the nervous system. Given the known mechanism of action of venlafaxine and the risk of serotonin syndrome, caution should be exercised when using venlafaxine and drugs with a possible effect on serotonergic transmission of nerve impulses (e.g., tryptan, SSRIs or lithium preparations).
The risk of concomitant use of venlafaxine and other drugs that affect the central nervous system (including the drugs described above) was not systematically evaluated. Therefore, with the combined use of venlafaxine and other similar drugs, caution is recommended.
Indinavir. With the simultaneous use of venlafaxine with indinavir, a decrease in AUC and C was notedmax indinavir by 28 and 36%, respectively. However, indinavir did not affect the pharmacokinetics of venlafaxine and EFA.
Warfarin. In patients receiving warfarin, after initiation of venlafaxine treatment, potentiation of the anticoagulant effect is possible, while the prothrombin time increases.
Diazepam. Venlafaxine does not affect the pharmacokinetics and pharmacodynamics profile of diazepam and its metabolite, desmethyl-diazepam. The use of venlafaxine did not affect the psychomotor and psychometric effects of diazepam.
Haloperidol. A study of the pharmacokinetics of haloperidol showed a decrease in renal clearance of 42%, an increase in Cmax in blood plasma by 88% and an increase in AUC of haloperidol by 70% without changing its T½. This should be considered with the combined use of haloperidol and venlafaxine.
Imipramine. Imipramine does not affect the pharmacokinetics of venlafaxine and EFA. Venlafaxine does not affect the pharmacokinetics of imipramine and 2-OH-imipramine. A dose-dependent increase in AUC of 2-OH-desimipramine was observed 2.5–4.5 times with venlafaxine at a dose of 75–150 mg / day. The clinical significance of this interaction is unknown. Caution should be exercised while using venlafaxine and imipramine.
Cimetidine. At equilibrium, cimetidine inhibited the first-pass venlafaxine metabolism, but did not significantly affect the formation and elimination of B-desmethyl-venlafaxine, which was in a much larger amount in the systemic circulation. Thus, obviously, with the parallel administration of cimetidine and venlafaxine to healthy adults, dose adjustment is not required. However, in elderly patients and those with impaired liver function receiving concurrent treatment with venlafaxine and cimetidine, drug interactions are unknown. Such patients need clinical monitoring.
Ethanol The introduction of venlafaxine according to the constant scheme did not potentiate the psychomotor and psychometric effects observed in the same individuals against the background of the absence of venlafaxine treatment.
Despite this, against the background of treatment with venlafaxine, it is recommended to avoid drinking alcohol.
Risperidone. With the simultaneous use of these drugs (despite an increase in AUC of risperidone), the pharmacokinetics of the sum of the active components (risperidone and its active metabolite) does not change significantly.
Lithium preparations. Venlafaxine does not affect the pharmacokinetic characteristics of lithium preparations.
Drugs that inhibit CYP 2D6. Isoenzyme CYP 2D6, responsible for genetic polymorphism, has been identified with respect to the metabolism of many antidepressants, transforming venlafaxine into its main active metabolite, EFA. Thus, there is the possibility of a drug interaction between venlafaxine and drugs that are CYP 2D6 inhibitors.
Drug interactions leading to a decrease in the conversion of venlafaxine to EFA (see Imipramine) potentially increase the concentration of venlafaxine in serum and lower the concentration of its active metabolite.
The pharmacokinetics profile of venlafaxine in the examined individuals who received one CYP 2D6 [inhibitor] at the same time cannot differ significantly from the pharmacokinetics profile in individuals with low metabolizing ability of CYP 2D6 (see Metabolism). For this reason, dose adjustment is not required.
Drugs that break down / metabolize under the influence of the cytochrome P450 enzyme
Venlafaxine does not inhibit the metabolism of diazepam, which partially breaks down under the influence of 2C19.
Venlafaxine is a relatively weak CYP 2D6 inhibitor.
Venlafaxine is combined with plasma proteins by 27%, while EFA - by 30%. Thus, drug interactions due to the combination of venlafaxine and its main metabolite with proteins may not be expected.