Pharmacy World & Science

, Volume 29, Issue 6, pp 577–583 | Cite as

Efficacy of diphenhydramine against cough in humans: a review

  • Ingunn BjörnsdóttirEmail author
  • Thomas Ray Einarson
  • Lárus Steinþór Guðmundsson
  • Rannveig Alma Einarsdóttir
Review Paper



To determine the efficacy of diphenhydramine against cough due to respiratory infection or irritation in patients/subjects without comorbidities.


Two reviewers independently identified English language studies, searching on: clinical trials, randomized, diphenhydramine (OR dimenhydrinate), antitussive agents, cough (combine using AND). Sources were: Medline (1966–2005), Embase (1980–2005), Cochrane and references from retrieved articles. Two other reviewers, blinded to study origin selected studies, inclusion criteria being: diphenhydramine monotherapy against placebo, double-blinded, randomized, clinical trial, intention-to-treat, dropout information. The blinded reviewers evaluated the selected studies on a quality scale.


Eleven articles were identified, 7 were rejected (4 not placebo controlled, 2 had no diphenhydramine, 1 not blinded), leaving 4 articles, that were included in the evaluation and scored 20, 21, 25 and 26 out of a maximum of 32. In these selected studies, a total of 162 people were examined, 65 on diphenhydramine, 63 on placebo and 34 in a crossover setting. There was a total of 13 dropouts. The crossover studies demonstrated significant effect; 27–56% reduction in 20 healthy volunteers and 21–26% reduction in 13 patients (originally 14, one outlier left out), whereas the active versus placebo studies did not.


In spite of the 60 years that the substance has been on the market, only few studies have properly evaluated the effect of diphenhydramine against cough. Presumptions about efficacy of diphenhydramine against cough in humans are not univocally substantiated in literature.


Antitussive Cough Diphenhydramine Efficacy Evidence based pharmacotherapy Review 



The study was done partly in the authors’ own time and partly while the first author was on a post doctoral fellow grant at the University of Toronto. The authors want to thank for constructive reviewer comments and editorial comments. The authors have no conflicts of interests to declare.


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Ingunn Björnsdóttir
    • 1
    Email author
  • Thomas Ray Einarson
    • 2
  • Lárus Steinþór Guðmundsson
    • 3
  • Rannveig Alma Einarsdóttir
    • 4
  1. 1.Department of Pharmacology and Pharmacotherapy, Section for Social Pharmacy, Faculty of Pharmaceutical SciencesUniversity of CopenhagenCopenhagenDenmark
  2. 2.Leslie Dan Faculty of PharmacyUniversity of TorontoTorontoCanada
  3. 3.Department of Pharmacology and ToxicologyUniversity of IcelandReykjavikIceland
  4. 4.Faculty of PharmacyUniversity of IcelandReykjavíkIceland

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