Can I take an antihistamine while taking benzonatate 100 mg?

No. Benzonatate may interact with other medications that cause drowsiness including, cough and cold medications, antihistamines, anti-seizure drugs, medicine for sleep or anxiety, muscle relaxants, narcotics, or psychiatric medicines. Avoid operating heavy machinery after you have taken Benzonatate as it may cause drowsiness and create more drowsiness if taken with any of the drugs listed above.