Robitussin DM Side Effects

Robitussin-DM is a common, over-the-counter cold medicine that temporarily relieves coughing and loosens mucus in the respiratory system. It contains two active ingredients: dextromethorphan, which is a cough suppressant, and guaifenesin, which is an expectorant. Though side effects are usually not serious, you should be aware of them, and if they persist or worsen, be sure to see your doctor.

Dizziness

• Dizziness, confusion and hallucinations are serious but rare side effects. Stop using the medication immediately and see your doctor.

Drowsiness

• Robitussin tends to cause drowsiness, impair clear thinking and slow down reaction time, so avoid driving or any other activity that requires alertness. Avoid drinking alcohol, too, as that can exacerbate this side effect.

Upset Stomach

• An upset stomach is another minor but common side effect when using Robitussin DM or any other medicine that contains dextromethorphan and guaifenesin. An upset stomach can include nausea, vomiting and constipation.

Allergic Reactions

• Allergic reactions--such as hives, itching, rash, swelling of the mouth or face, difficulty breathing or tightness in the chest--may occur when taking this medicine. These side effects are severe and should be checked out by a doctor right away.

Restlessness

• Overdosing on this medication may cause restlessness, nervousness, rapid heartbeat and high or low blood pressure. Two teaspoons every four hours is the recommended dose.

Poisoning

• If you take Robitussin DM (or any product that has dextromethorphan and guaifenesin) with an MAO inhibitor--which is an enzyme commonly used in such antidepressants as Isocarboxazid, Phenelzine, Tranylcypromine or Selegeline--within the past 14 days, you may experience severe side effects, such as poisoning or death.