Brief Answer:
If you take one inadvertent double dose nothing will happen

Detailed Answer:
Thanks for asking on HealthcareMagic.

I have gone carefully through your query and understand your concerns. If you take double the dose of Celexa (Citalopram) you may observe the following side effects:
drowsiness, tired feeling
sleep problems (insomnia)
mild nausea, diarrhea, upset stomach, dry mouth
cold symptoms such as stuffy nose, sneezing, sore throat, cough
increased sweating or urination, weight changes
decreased sex drive, impotence, or difficulty having an orgasm

Please note that if you take one inadvertent double dose nothing will possibly happen it is only if you take higher doses for prolonged durations that the above may be observed.

Let me know if I could help further.

Regards

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