Hi Mrs., thank you for your question!
I found the product you are talking about, and it is basically a multivitamin. There are no problems taking this product with citalopram.
To answer your question more broadly, unfortunately no over-the-counter product is proven to improve concentration.
Some studies mention Omega-3 supplements, but again, they are inconclusive, and the amounts and concentrations of Omega-3 vary from study to study, and if you eat 2 fish meals a week, supplementation only becomes redundant.
For your study environment, minimize distractions, such as cell phones, computers, television and noise... write down your study goals on a list to track your progress and stay on track.
Take frequent breaks (like every hour).
Finally, exercise and enough sleep can go a long way in helping you relax and absorb the material you are studying.
I hope I have helped you. Feel free to contact me if you have any other questions, good luck with the new school year :)!
Tom Samaha, pharmacist