Side Effects of Pristiq (desvenlafaxine)

Pristiq (desvenlafaxine) is a serotonin and norepinephrine reuptake inhibitor (SNRI) antidepressant used to treat depression. 

Pristiq affects neurotransmitters, the chemicals that nerves within the brain make and release in order to communicate with each other. Neurotransmitters either travel across the space between nerves and attach to receptors on the surface of nearby nerves or they attach to receptors on the surface of the nerves that produce them, to be taken up by the nerve and released again (a process referred to as re-uptake). 

Experts believe an imbalance among neurotransmitters is the cause of depression. Serotonin and norepinephrine are two neurotransmitters released by nerves in the brain. Pristiq works by preventing the reuptake of serotonin and epinephrine by nerves after they have been released. 

Since uptake is an important mechanism for removing released neurotransmitters and terminating their actions on adjacent nerves, the reduced uptake caused by Pristiq increases the effect of serotonin and norepinephrine in the brain. 

Common side effects of Pristiq include

• nausea,
• headaches,
• anxiety,
• insomnia,
• drowsiness,
• constipation,
• weakness,
• dry mouth,
• sweating,
• diarrhea,
• sexual dysfunction (decreased sex drive and delayed orgasm and ejaculation), and
• loss of appetite. 

Serious side effects of Pristiq include

• increased blood pressure,
• seizures,
• increased risk of gastrointestinal bleeding, and
• increased risk of suicidal thinking and behavior (suicidality) in children and adolescents with depression and other psychiatric disorders.

Withdrawal reactions such as anxiety, nausea, nervousness, and insomnia may occur when Pristiq is suddenly stopped. 

Drug interactions of Pristiq include oxidase inhibitors (MAOIs) or other drugs that inhibit monoamine oxidase (for example, linezolid) because such combinations may lead to confusion, high blood pressure, tremor, hyperactivity, coma, and death.

• Pristiq should not be administered within 14 days after stopping MAOIs and MAOIs should not be administered within 7 days of stopping Pristiq.
• Similar reactions may occur if Pristiq is combined with other SNRIs, selective serotonin reuptake inhibitors (SSRIs) or other drugs that increase serotonin in the brain, for example, tryptophan, St. John's wort, meperidine, or tramadol.
• SNRIs may increase the effect of warfarin, leading to excessive bleeding.
• Combining SNRIs with aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) or other drugs that affect bleeding may increase the likelihood of upper gastrointestinal bleeding.
• Ketoconazole may reduce the breakdown of Pristiq, therefore increasing concentrations of Pristiq in the body and the risk of adverse effects.
• Pristiq may reduce the concentration of midazolam. 

There are no adequate and well-controlled studies of Pristiq in pregnant women. Pristiq is secreted in breast milk. Mothers who are taking Pristiq should discuss with their doctor whether to not breastfeed or to discontinue Pristiq.

Desvenlafaxine can cause

• nausea,
• headaches,
• anxiety,
• insomnia,
• drowsiness,
• constipation,
• weakness,
•  dry mouth,
• sweating,
• diarrhea, and
• loss of appetite.

Increased blood pressure can occur and should be monitored. Seizures have been reported. Sexual dysfunction (decreased sex drive and delayed orgasm and ejaculation) has been associated with desvenlafaxine. Desvenlafaxine and other SNRIs may increase the risk of gastrointestinal bleeding.

Some patients may experience withdrawal reactions upon stopping desvenlafaxine. Symptoms of withdrawal include

• anxiety,
• nausea,
• nervousness, and
• insomnia.

The dose of desvenlafaxine should be gradually reduced when therapy is discontinued to prevent symptoms of withdrawal.

Antidepressants increased the risk of suicidal thinking and behavior (suicidality) in short-term studies in children and adolescents with depression and other psychiatric disorders.

Anyone considering the use of desvenlafaxine or any other antidepressant in a child or adolescent must balance this risk with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidality, or unusual changes in behavior.

The following adverse reactions are discussed in greater detail in other sections of the label.

• Hypersensitivity
• Suicidal Thoughts and Behaviors in Adolescents and Young Adults
• Serotonin Syndrome
• Elevated Blood Pressure
• Abnormal Bleeding
• Angle Closure Glaucoma
• Activation of Mania/Hypomania
• Discontinuation Syndrome
• Seizure
• Hyponatremia
• Interstitial Lung Disease and Eosinophilic Pneumonia

Clinical Studies Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in clinical practice.

Patient Exposure

• Pristiq was evaluated for safety in 8,394 patients diagnosed with major depressive disorder who participated in multiple-dose pre-marketing studies, representing 2,784 patient-years of exposure.
• Of the total 8,394 patients exposed to at least one dose of Pristiq; 2,116 were exposed to Pristiq for 6 months, representing 1,658 patient-years of exposure, and 421 were exposed for one year, representing 416 patient-years of exposure.

Adverse Reactions Reported As Reasons For Discontinuation Of Treatment

• In the pre-marketing pooled 8-week placebo-controlled studies in patients with MDD, 1,834 patients were exposed to Pristiq (50 to 400 mg).
• Of the 1,834 patients, 12% discontinued treatment due to an adverse reaction, compared with 3% of the 1,116 placebo-treated patients.
• At the recommended dose of 50 mg, the discontinuation rate due to an adverse reaction for Pristiq (4.1%) was similar to the rate for placebo (3.8%).
• For the 100 mg dose of Pristiq the discontinuation rate due to an adverse reaction was 8.7%.
• The most common adverse reactions leading to discontinuation in at least 2% and at a rate greater than placebo of the Pristiq treated patients in the short-term studies, up to 8 weeks, were:
  • nausea (4%);
  • dizziness, headache and vomiting (2% each).
• In a longer-term study, up to 9 months, the most common was vomiting (2%).

Common Adverse Reactions In Placebo-Controlled MDD Studies

• The most commonly observed adverse reactions in Pristiq treated MDD patients in premarketing pooled 8-week, placebo-controlled, fixed-dose studies (incidence ≥ 5% and at least twice the rate of placebo in the 50 or 100 mg dose groups) were:
  • nausea,
  • dizziness,
  • insomnia,
  •  hyperhidrosis,
  • constipation,
  • somnolence,
  • decreased appetite,
  • anxiety, and
  • specific male sexual function disorders.
• Table 2 shows the incidence of common adverse reactions that occurred in ≥ 2% of Pristiq treated MDD patients and twice the rate of placebo at any dose in the pre-marketing pooled 8week, placebo-controlled, fixed dose clinical studies

Table 2: Common Adverse Reactions (≥ 2% in any Fixed-Dose Group and Twice the Rate of Placebo) in Pre-marketing Pooled MDD 8-Week Placebo-Controlled Studies

Sexual Function Adverse Reactions

• Table 3 shows the incidence of sexual function adverse reactions that occurred in ≥ 2% of Pristiq treated MDD patients in any fixed-dose group (pre-marketing pooled 8-week, placebo-controlled, fixed -dose, clinical studies).

Table 3: Sexual Function Adverse Reactions (≥ 2% in Men or Women in any Pristiq Group) During the On-Therapy Period

Other Adverse Reactions Observed In Premarketing And Postmarketing Clinical Studies

Other infrequent adverse reactions, not described elsewhere in the label, occurring at an incidence of < 2% in MDD patients treated with Pristiq were:

• Cardiac disorders - Tachycardia.
• General disorders and administration site conditions - Asthenia.
• Investigations - Weight increased, liver function test abnormal, blood prolactin increased.
• Musculoskeletal and connective tissue disorders - Musculoskeletal stiffness.
• Nervous system disorders -Syncope, convulsion, dystonia.
• Psychiatric disorders - Depersonalization, bruxism.
• Renal and urinary disorders - Urinary retention.
• Skin and subcutaneous tissue disorders - Rash, alopecia, photosensitivity reaction, angioedema.

In clinical studies, there were uncommon reports of ischemic cardiac adverse reactions, including myocardial ischemia, myocardial infarction, and coronary occlusion requiring revascularization; these patients had multiple underlying cardiac risk factors. More patients experienced these events during Pristiq treatment as compared to placebo.

Laboratory, ECG And Vital Sign Changes Observed In MDD Clinical Studies

The following changes were observed in pre-marketing placebo-controlled, short-term MDD studies with Pristiq.

Lipids

Elevations in fasting serum total cholesterol, LDL (low density lipoproteins) cholesterol, and triglycerides occurred in the controlled studies. Some of these abnormalities were considered potentially clinically significant.

The percentage of patients who exceeded a predetermined threshold value is shown in Table 4.

Table 4: Incidence (%) of Patients With Lipid Abnormalities of Potential Clinical Significance*

Proteinuria

Proteinuria, greater than or equal to trace, was observed in the pre-marketing fixed-dose controlled studies (see Table 5). This proteinuria was not associated with increases in BUN or creatinine and was generally transient.

Table 5: Incidence (%) of Patients with Proteinuria in the Fixed-dose Clinical Studies

Vital Sign Changes

Table 6 summarizes the changes that were observed in placebo-controlled, short-term, pre-marketing studies with Pristiq in patients with MDD (doses 50 to 400 mg).

Table 6: Mean Changes in Vital Signs at Final on Therapy for All Short-term, Fixed-dose Controlled Studies

Treatment with Pristiq at all doses from 50 mg per day to 400 mg per day in controlled studies was associated with sustained hypertension, defined as treatment-emergent supine diastolic blood pressure (SDBP) ≥90 mm Hg and ≥10 mm Hg above baseline for 3 consecutive on-therapy visits (see Table 7).

Analyses of patients in Pristiq pre-marketing short-term controlled studies who met criteria for sustained hypertension revealed a consistent increase in the proportion of patients who developed sustained hypertension. This was seen at all doses with a suggestion of a higher rate at 400 mg per day.

Table 7: Proportion of Patients with Sustained Elevation of Supine Diastolic Blood Pressure

Orthostatic Hypotension

In the pre-marketing short-term, placebo-controlled clinical studies with doses of 50 to 400 mg, systolic orthostatic hypotension (decrease ≥30 mm Hg from supine to standing position) occurred more frequently in patients ≥65 years of age receiving Pristiq (8%, 7/87) versus placebo (2.5%, 1/40), compared to patients <65 years of age receiving Pristiq (0.9%, 18/1,937) versus placebo (0.7%, 8/1,218).

Postmarketing Experience

The following adverse reaction has been identified during post-approval use of Pristiq. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure:

• Skin and subcutaneous tissue disorders - Stevens-Johnson syndrome.
• Gastrointestinal disorders - Pancreatitis acute.
• Cardiovascular system - Takotsubo cardiomyopathy.

Monoamine Oxidase Inhibitors (MAOI)

• Do not use MAOIs intended to treat psychiatric disorders with desvenlafaxine or within 7 days of stopping treatment with desvenlafaxine.
• Do not use desvenlafaxine within 14 days of stopping an MAOI intended to treat psychiatric disorders.
• In addition, do not start desvenlafaxine in a patient who is being treated with linezolid or intravenous methylene blue.

Serotonergic Drugs

• Based on the mechanism of action of desvenlafaxine and the potential for serotonin syndrome, caution is advised when desvenlafaxine is co-administered with other drugs that may affect the serotonergic neurotransmitter systems.

Drugs That Interfere With Hemostasis (e.g., NSAIDs, Aspirin, and Warfarin)

• Serotonin release by platelets plays an important role in hemostasis.
• Epidemiological studies of case-control and cohort design that have demonstrated an association between use of psychotropic drugs that interfere with serotonin reuptake and the occurrence of upper gastrointestinal bleeding.
• These studies have also shown that concurrent use of an NSAID or aspirin may potentiate this risk of bleeding.
• Altered anticoagulant effects, including increased bleeding, have been reported when SSRIs and SNRIs are co-administered with warfarin.
• Patients receiving warfarin therapy should be carefully monitored when Pristiq is initiated or discontinued.

Potential For Other Drugs To Affect Desvenlafaxine

• Based on in vitro data, no dose adjustment is required for Pristiq when used concomitantly with inhibitors of CYP3A4 and CYP1A1, 1A2, 2A6, 2D6, 2C8, 2C9, 2C19, 2E1, and the P-glycoprotein transporter.
• Clinical studies have demonstrated no clinically significant pharmacokinetic interaction between Pristiq and strong CYP 3A4 inhibitors (Figure 1).

Figure 1 : Impact of other drugs on Desvenlafaxine Pharmacokinetics (PK)

Impact of other drugs on Desvenlafaxine Pharmacokinetics Illustration

Potential For Desvenlafaxine To Affect Other Drugs

• Clinical studies have shown that desvenlafaxine does not have a clinically relevant effect on CYP2D6 metabolism at the dose of 100 mg daily (Figure 2).
• Substrates primarily metabolized by CYP2D6 (e.g., desipramine , atomoxetine, dextromethorphan, metoprolol, nebivolol, perphenazine, tolterodine) should be dosed at the original level when co-administered with Pristiq 100 mg or lower or when Pristiq is discontinued.
• Reduce the dose of these substrates by up to one-half if co-administered with 400 mg of Pristiq.
• No additional dose adjustment is required for concomitant use of substrates of CYP3A4, 1A2, 2A6, 2C8, 2C9, and 2C19 isozymes, and P-glycoprotein transporter.
• Clinical studies have demonstrated no clinically significant pharmacokinetic interaction between Pristiq and CYP3A4 substrates (Figure 2).
• Clinical studies have shown that desvenlafaxine (100 mg daily) does not have a clinically relevant effect on tamoxifen and aripiprazole, compounds that are metabolized by a combination of both CYP2D6 and CYP3A4 enzymes (Figure 2).
• In vitro studies showed minimal inhibitory effect of desvenlafaxine on the CYP2D6 isoenzyme.
• In vitro, desvenlafaxine does not inhibit or induce the CYP3A4 isozyme.
• In vitro, desvenlafaxine does not inhibit CYP1A2, 2A6, 2C8, 2C9, and 2C19, isozymes, and P-glycoprotein transporter and would not be expected to affect the pharmacokinetics of drugs that are substrates of these CYP isozymes and transporter.

Figure 2 : Impact of Desvenlafaxine on Pharmacokinetics (PK) of Desipramine, Midazolam, Tamoxifen and Aripiprazole

Impact of Desvenlafaxine on Pharmacokinetics (PK) of Desipramine, Midazolam, Tamoxifen and Aripiprazole Illustration

Other Drugs Containing Desvenlafaxine Or Venlafaxine

• Avoid use of Pristiq with other desvenlafaxine-containing products or venlafaxine products.
• The concomitant use of Pristiq with other desvenlafaxine-containing products or venlafaxine will increase desvenlafaxine blood levels and increase dose-related adverse reactions.

Ethanol

• A clinical study has shown that Pristiq does not increase the impairment of mental and motor skills caused by ethanol.
• However, as with all CNS-active drugs, patients should be advised to avoid alcohol consumption while taking Pristiq.

Drug-Laboratory Test Interactions

• False-positive urine immunoassay screening tests for phencyclidine (PCP) and amphetamine have been reported in patients taking desvenlafaxine.
• This is due to lack of specificity of the screening tests. False positive test results may be expected for several days following discontinuation of desvenlafaxine therapy.
• Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish desvenlafaxine from PCP and amphetamine.

Drug Abuse And Dependence

Controlled Substance

Pristiq is not a controlled substance.