i understand your concern for your mother. Pristiq (desvenlafaxine) is an antidepressant in a group of drugs called selective serotonin and norepinephrine reuptake inhibitors (SNRIs). Desvenlafaxine is used to treat major depressive disorder. Common side effects include drowsiness, dizziness, nausea, dry mouth, constipation, loss of appetite, weight loss, blurred vision, nervousness, trouble sleeping, or excessive sweating may occur. If any of these effects persist or worsen, inform your doctor promptly. It is important that you stay strong for your mother. Talk to your doctor for dosage adjustments, but you also need to understand that mother is going through a major depressive phase, give her some time to adjust with the medication. Take Care