Effexor is known to increase blood pressure and so is Zyrtec-D, not plain Zyrtec. The D component of Zyrtec-D is pseudoephedrine and any product with that ingredient (Sudafed, Claritin-D) is not recommended with patients who have hypertension or increased ocular pressure (increased pressure in the eyes). The reason is because the pseudoephedrine constricts the blood vessels and as a result increases pressure. Effexor as well increases blood pressure due to how the medication works. So in combination, Effexor has been seen to increase the activity of Zyrtec-D. Therefore Effexor and Zyrtec-D together can increase the pressure in your eyes leading to hypertension. The usual case is that you may have already had increased pressure in the eyes and taking these medications may have contributed the problem.