Is it safe to continue taking Pristiq (desvenlafaxine) 100mg for 8 years, as it only controls sweating symptoms?

Pristiq for Hyperhidrosis: Long-Term Use Assessment

If Pristiq 100mg is effectively controlling hyperhidrosis (excessive sweating) after 8 years of use, it is reasonable to continue the medication, but this represents off-label use that requires ongoing monitoring for cardiovascular effects, particularly blood pressure and heart rate, as well as periodic reassessment of whether the benefit justifies continued SNRI exposure.

Clinical Context and Off-Label Use

The patient is using desvenlafaxine (Pristiq) for hyperhidrosis control, which is not an FDA-approved indication. Desvenlafaxine is approved only for major depressive disorder in adults 1, 2. However, the mechanism of action—serotonin-norepinephrine reuptake inhibition—can affect autonomic nervous system function and potentially reduce sweating in some patients 3.

Safety Considerations for Long-Term Use

Cardiovascular Monitoring Requirements

• Blood pressure and heart rate must be monitored periodically during long-term SNRI therapy, as desvenlafaxine can cause hypertension and cardiovascular effects 3
• Hypertension, QTc interval prolongation, and exacerbation of ischemic cardiac disease have been reported with desvenlafaxine 3
• At 53 years of age, cardiovascular risk assessment becomes increasingly important with continued SNRI exposure 3

Metabolic and Laboratory Monitoring

• Elevated lipids and elevated liver enzymes have been documented with desvenlafaxine use 3
• Periodic laboratory monitoring should include lipid panels and hepatic function tests 3

Dose Considerations

• The standard approved dose for desvenlafaxine is 50 mg daily, with no additional therapeutic benefits demonstrated at doses above 50 mg/day for depression 2
• The patient is taking 100 mg, which is at the upper end of the recommended dosing range (50-100 mg) 4
• Doses above 100 mg/day show incremental increases in side effects without additional benefit 4

Risk-Benefit Analysis

Potential Benefits of Continuation

• Desvenlafaxine has demonstrated good tolerability in clinical practice with favorable safety profile 5
• The medication has low risk of drug-drug interactions due to minimal CYP450 metabolism 3, 4
• Eight years of successful symptom control suggests individual therapeutic response 5

Potential Risks of Continuation

• Nausea is the most common adverse effect, though typically diminishes over time 2, 3
• Cardiovascular effects including hypertension require ongoing surveillance 3
• Discontinuation syndrome can occur if the medication is stopped abruptly, characterized by dizziness, fatigue, nausea, insomnia, anxiety, and sensory disturbances 6

Alternative Considerations

Other Medications for Hyperhidrosis

While not directly addressed in the provided evidence, the patient should be aware that:

• Anticholinergic agents are the standard pharmacologic treatment for hyperhidrosis, though they have their own side effect profiles
• Topical treatments may provide localized control with fewer systemic effects
• The off-label use of an SNRI for hyperhidrosis alone may not represent optimal therapy

If Discontinuation is Considered

• Taper slowly over a minimum of 10-14 days to minimize discontinuation syndrome 6
• Expect potential withdrawal symptoms including anxiety, agitation, dizziness, and physical discomfort 6
• Monitor for rebound hyperhidrosis after discontinuation

Monitoring Protocol for Continued Use

Implement the following surveillance schedule:

• Blood pressure and heart rate checks every 3-6 months 3
• Annual lipid panel and liver function tests 3
• Annual reassessment of symptom control and quality of life impact
• Evaluation for emergence of new cardiovascular risk factors
• Assessment for any new medication interactions given desvenlafaxine's CYP2D6 weak inhibition 4

Common Pitfalls to Avoid

• Do not abruptly discontinue if cessation is desired—always taper gradually 6
• Do not ignore cardiovascular monitoring simply because the patient has tolerated the medication for years; cumulative cardiovascular risk increases with age 3
• Do not assume FDA-approved dosing for depression applies to off-label hyperhidrosis use—the optimal dose for sweating control may differ
• Avoid NSAIDs if considering medication changes, as there is increased bleeding risk with SNRIs 6