Yes, Effexor reduces sexual desire. I tried it and I knew that. For that, I switched it. I'm now on Pristiq which is Effexor metabolite. Pristiq is less side effects. Both may work differently. For me, Pristiq work better. Pristiq may also reduce sexual desire but not like Effexor. Also, it work differently from one to another.
Google on Pristiq if it available where you live.