What should you take to soothe a bad cough? Experts from the American College of Chest Physicians have issued guidelines … and their advice may surprise you.

Here’s some counterintuitive news: The most effective medicines for a cough aren’t marketed as cough treatments. The American College of Chest Physicians (ACCP) has issued comprehensive guidelines for treating various types of cough, the number one reason people seek medical attention. The guidelines state that many of the key ingredients in cough and cold medications don’t effectively quiet coughs that are caused by the common cold.

They stress that most over-the-counter cough expectorants or suppressants, including cough syrups and cough drops, just don’t work. Instead, certain older allergy and pain medicines are more effective for treating coughs, even though they aren’t advertised as cough busters.

After reviewing studies done from 1980 to 2004 on cough and the common cold, an ACCP expert panel found that guaifenesin -- an expectorant found in such popular cough medicines as Robitussin and Mucinex -- is not effective in controlling cough caused by the common cold. Guaifenesin is supposed to thin mucus and make it easier to cough up phlegm.

Of the four studies, which compared guaifenesin with a placebo, two showed that the cough medicine was effective, but two showed it was not. The ACCP concluded that this was not enough evidence to say that the drug is effective for treating coughs due to colds.

Two other common cough treatments, dextromethorphan and codeine, also didn’t pass muster for treating coughs caused by colds. The experts found that the dose of dextromethorphan used in over-the-counter brands is ineffective. Even large doses of codeine didn’t work. Although neither drug is effective for coughs from the common cold, both drugs may help people with chronic bronchitis get short-term relief from coughing, the panel noted. It also found that the ever-popular zinc and echinacea were ineffective for coughs due to colds.

So What Does Work? The panel members didn’t merely knock popular cough remedies off their pedestal. They did find some over-the-counter products that can help to calm coughs -- but not the ones you’d expect.

Antihistamine/decongestant medications that contain brompheniramine and sustained-release pseudoephedrine can be effective, they found. These medications contain older antihistamines that can make you drowsy. However, newer non-sedating antihistamines don’t work for reducing cough, the panel concluded. Another treatment to try is the pain reliever naproxen (Aleve), which the panel said has been shown to decrease the severity and frequency of coughing.