Why does guanfacine make me urinate frequently?

Unusual: Guaifenesin is an expectorant and there is no diuretic effect with this medication. It will cause dry mouth, and perhaps the subsequent thirst and drinking of fluids results in the increased frequency of urination.

Guanfacine: I suspect that this is rare. Drugs.Com reported urinary frequency with Intuniv but the actual frequency of this side effect is not reported. I would not know the mechanism of action.