My husband has copd and refuses to quit smoking. his doctor has recommended mucinex (guaifenesin) d. are there any serious side effects from long term use of mucinex (guaifenesin) d?

None: Probably Mucinex (guaifenesin) plain is much safer. D has some antihistamine in it, which may cause some dryness of mucus membrane and drowsiness. Otherwise it should be safe.

No: It's generally safe when used as directed.

Mucinex (guaifenesin) d: The major risk is with the d or decongestant component. It can cause persistent high blood pressure in excess of that caused by every drag of the cigarette. An option is just regular mucinex (guaifenesin).