Im finding it hard to type at the moment. How quick can side effects come on?

Because I took Citalopram at 9.30am, and by 11am I started to feel very, very sick. It's now 45 minutes later, my stomach wants to wretch and Im not sure im seeing normally either.

it's either the medication, or last nights mince.

I'm just wondering if anyone has experience with this SSRI anti depressant drug used for anxiety and have experienced this, or if generally people have experienced such sudden nausea or side effects so soon after taking a medication?