Can you take penicillin with cough syrup?

It depends what your antibiotics are for. If you are taking antibiotics to treat a bronchial, lung, or throat infection, I would say stay away from any cough syrup containing dextromethorphan. This suppresses your cough, which is your body's natural defense against foreign material in your airway. Think about it. You have bacteria trying to grow into a colony in your throat. If you keep coughing them up, they will have a much harder time growing and thriving. If you suppress your cough, they will be able to settle down without much disturbance.

However, if you get a cough syrup with guaifenesin as it's active ingredient, that may be best. Guaifenesin does not stop you from coughing, but helps you cough up whatever is in your airway better. It breaks up all that phlegm in there and allows it to pass. This may be your best bet. Just be SURE to drink a full glass of water with each dose of Guaifenesin. You will be surprised how much it helps!

However, if your antibiotic is for some other type of infection, like an ear infection or something not related to your cough at all, I would guess any type of cough syrup is fine.

Remember, DM is for a DRY cough, and Guaifenesin is for a wet cough.

It is best to ask the Doctor Who perscribed the antibiotic, or consult with a pharmacist. They know these things very well.