Are there any known interactions between celexa (citalopram) and anti acids such as tums?

No : After looking on epocrates, no interactions are noted between Tums and celexa (citalopram). For complete safety, always check with the pharmacist when a new medicine is added, even if it is over the counter.

Check: You can use a drug interaction checker whenever you have questions about drug-drug interactions or drug - food interactions. Here is one option (Drugs.Com): https://www.drugs.com/drug_interactions.php Your pharmacist is also an excellent source of information.