The investigators hypothesis is that obstructive sleep apnea (OSA) patients with a low arousal threshold may wake up too early during a respiratory event, before upper airway muscles can be activated to achieve stable ventilation. Thus, strategies to manipulate the respiratory arousal threshold could potentially improve the quality of sleep and sleep disordered breathing. Agents that raise arousal threshold are therefore likely to benefit some patients with OSA. The overall goal of this project is to determine the importance of the arousal threshold in OSA, determine which patients might benefit from a raised arousal threshold, and test this hypothesis by using pharmacological manipulation of the arousal threshold to achieve this goal.

This study is a randomized double-blinded crossover pilot study. The investigators will test whether Venlafaxine has important effects on the apnea hypopnea index. Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI) for the treatment of depression and anxiety. Venlafaxine increases serum serotonin level, which may affect arousal threshold. Furthermore, higher serotonin level theoretically may improve muscle tone, including upper airway muscle. Therefore, the investigators hypothesize that venlafaxine may decrease arousal threshold and improve muscle tone, leading to improvement of OSA.

Eligible participants will undergo overnight polysomonography as described below and will receive either Venlafaxine(50 mg 2 hour prior to sleep) or placebo (in random order) followed roughly 7 days later with placebo or donepezil. This aim will allow us to test the impact of Venlafaxine on the apnea hypopnea index.

The change in apnea hypopnea index will be compared in the Venlafaxine groups with the placebo group.

Inclusion Criteria:

• Ages 18-70 years
• sleep study (with apnea hypopnea index>5)
• Diagnosis of obstructive sleep apnea

Exclusion Criteria:

• Any known cardiac (apart from treated hypertension), pulmonary (including uncontrolled asthma), renal, neurologic (including epilepsy), neuromuscular, or hepatic disease.
• Susceptible to stomach ulcers.
• co-administration of MAO inhibitors intended to treat psychiatric disorders (concurrently or within 14 days of discontinuing the MAO inhibitor); initiation of MAO inhibitor intended to treat psychiatric disorders within 7 days of discontinuing venlafaxine; initiation in patients receiving linezolid or intravenous methylene blue
• Pregnant women.
• History of hypersensitivity to Afrin, Lidocaine (all Aims) or venlafaxine
• History of bleeding diathesis and/or gastrointestinal bleeding.
• Glaucoma and Urinary Retention
• Use of any medications that may affect sleep or breathing.
• Use of any medications that have known interaction with venlafaxine and the interaction may significantly increase the risk of the subject or decrease the therapeutic effect of the medication.
• A psychiatric disorder, other than mild depression; e.g. schizophrenia, bipolar disorder, major depression, panic or anxiety disorders.
• Substantial cigarette (>5/day), alcohol (>3oz/day) or use of illicit drugs.
• More than 10 cups of beverages with caffeine (coffee, tea, soda/pop) per day.
• Desaturations to below 70% lasting greater than 10 seconds in duration per event

Age 35-64 years