Which symptomatic treatments have the best evidence for shortening cough duration in adults with the common cold?

1. Combination first‑generation antihistamine + decongestant: the clearest positive signal

Multiple guideline reviews and randomized trials single out an older, sedating antihistamine paired with an effective decongestant (for example, brompheniramine plus sustained‑release pseudoephedrine) as producing faster improvement in cough, postnasal drip and throat clearing compared with placebo, and this is described in ACCP and other clinical summaries as the best-supported pharmacologic option for cold‑related cough ^{[7] [1] [2]}.

2. Anti‑inflammatories and anticholinergics: naproxen and ipratropium have niche roles

Some trials found that the NSAID naproxen reduced cough and systemic symptoms in experimentally induced rhinovirus colds, leading guidelines to list naproxen as an option to decrease cough in certain settings ^{[8] [2]}, while intranasal ipratropium is documented as helpful for rhinorrhea and has evidence for reducing cough linked to upper‑airway secretions in adult studies referenced in reviews ^[3].

3. Remedies with limited or inconsistent evidence: zinc, honey, cromolyn and phytotherapeutics

Meta‑analyses report that orally administered zinc lozenges can shorten overall cold duration by about a day in some studies, a signal that may indirectly reduce cough duration when taken early, but results are inconsistent across formulations and doses and adverse effects occur ^{[9] [10]}; honey is recommended cautiously by panels for cough relief though most randomized evidence focuses on children and direct adult comparative data are sparse ^{[3] [11]}; small trials suggest intranasal cromolyn and some combination phytotherapeutics may hasten symptom resolution including cough, but these data are limited and not universally reproduced ^{[11] [12]}.

4. Commonly used medicines that do not shorten cough duration

Nonsteroidal anti‑inflammatory drugs such as ibuprofen and acetaminophen relieve aches and fever but do not improve cough or overall cold duration, and antitussives like codeine generally show no advantage over placebo for reducing cough urge in the common cold ^{[3] [13]}; newer nonsedating antihistamines are ineffective for cold cough and are not recommended for that indication ^{[7] [2]}.

5. The state of the evidence: modest effects, low quality, and important gaps

Systematic reviews and expert panels repeatedly conclude that the overall evidence base for shortening cough duration in the common cold is of low to moderate quality, that positive findings are often small in magnitude, and that heterogeneity in study designs, agents, doses and endpoints limits confidence—CHEST and other guideline documents explicitly call for higher‑quality randomized trials and validated outcome measures ^{[4] [5] [6]}.

6. Practical synthesis and where judgment applies

For adults seeking treatments most likely to shorten cold‑related cough, the evidence favors a short course of a first‑generation antihistamine combined with a decongestant (recognizing side effects such as sedation and cardiovascular stimulation), with naproxen or intranasal ipratropium as reasonable adjuncts in selected patients; zinc lozenges and certain nonprescription options may help but are inconsistent and have tolerability issues, while many popular remedies and antitussives lack proof of benefit—clinicians and patients must weigh modest potential gains against harms and the generally self‑limited nature of the illness ^{[1] [2] [8] [9] [3]}.