What adverse effect is associated with high doses of venlafaxine?

High doses of venlafaxine, a serotonin-norepinephrine reuptake inhibitor (SNRI), can lead to hypertension. This effect is primarily due to its action on norepinephrine reuptake; as the dosage increases, the inhibition of norepinephrine results in elevated blood pressure levels, particularly at doses above 300 mg per day. Clinicians monitoring patients on venlafaxine often check blood pressure, especially when initiating or adjusting doses, to mitigate the risk of hypertensive episodes.

Other potential adverse effects, such as nausea, weight gain, and sleep disturbances, are associated with venlafaxine but are generally more common at lower doses and do not escalate to the same degree as hypertension does at high doses. Hence, while nausea can occur as a side effect, it is less concerning in terms of safety compared to the significant cardiovascular risk presented by elevated blood pressure at higher therapeutic doses.