Table 1:

Characteristics of randomized controlled trials included in the qualitative analysis

StudyCountrynStudy periodPopulationType of coldZinc formulation, dosageDuration of symptoms before treatment, hDuration of treatmentDuration of follow-upDefinition of symptom resolutionFunding
Al-Nakib et al., 198726United Kingdom12NRAdults, age 18–50 yrIZG lozenge; 23 mg every 2 h while awake< 246 dNRNRPharma (RBS)
Douglas et al., 198727Australia55Apr–Nov 1985AdultsNZA lozenge; 10 mg every 2 h while awake (6–8 daily)< 48Until symptom resolution (minimum 3 d, maximum 6 d)14 dNo nasal, throat or cough symptomsPharma (Fauldings Ltd.)
Eby et al., 198428United States146Fall 1981Children and adultsNZG tablet; loading dose 46 mg, then 23 mg every 2 h while awake< 72Until symptom resolution7 dAbsence of all cold symptoms*Pharma (Truett laboratories)
Farr et al. (A), 198729United States32NRAdultsIZG lozenge (citric acid); loading dose 46 mg, then 23 mg every 2 h while awake< 365 dNRNRPharma (Bristol Myers)
Farr et al. (B), 198729United States45NRAdultsIZG lozenge (citric acid); 23 mg every 2 h while awake< 247 dNRNRPharma (Bristol Myers)
Godfrey et al., 199230United States87NRAdultsNZG lozenge (glycine); 23.7 mg every 2 h while awake (maximum 8)< 48Until symptom resolutionNRAbsence of all cold symptoms*Pharma (Rorer), Godfrey Science and Design Inc.
Kurugöl et al., 200631Turkey200Oct 2004–May 2005Children, age 2–10 yrNZS syrup; 15 mg twice daily< 24Until symptom resolution (maximum 10 d)7 moSymptom score ≤ 1† on 2 consecutive daysPharma (Berko Ilaç)
Kurugöl et al., 200732Turkey120Dec 2004–Mar 2005ChildrenNZS syrup; 15 mg twice daily< 4810 dUntil symptom resolution or 7 dResolution of all or all but one mild symptom*Pharma (Berko Ilaç)
Macknin et al., 199833United States249Oct 1996–Mar 1997Children, grades 1–12NZG lozenge (glycine); 10 mg five times daily (grades 1–6) or six times daily (grades 7–12)< 24Until symptom resolutionUntil symptom resolutionAbsence of nine symptoms* (excluding fever)Pharma (Quigley)
Mossad et al., 199634United States100Oct 1994–Nov 1994AdultsNZG lozenge (glycine); 13.3 mg every 2 h< 24Until symptom resolution18 dResolution of all or all but one mild symptom*Pharma (Quigley), Cleveland Clinic Foundation
Petrus et al., 199835United States102July 1997–Aug 1997AdultsNZA lozenge; 9 mg every 1.5 h on day 1, then every 2 h while awakeNRUntil symptom resolution (maximum 14 d)Until symptom resolutionResolution of 11 cold symptoms (10 listed* plus malaise)Pharma (Weider Nutrition)
Prasad et al., 200036United States50Jan 1998–Dec 1998AdultsNZA lozenge; 12.8 mg every 2–3 h while awake< 24Until symptom resolution1 d after symptom resolutionResolution of all or all but one mild symptom*George and Patsy Eby Research Foundation
Prasad et al., 200837United States50Jan 1999–Jan 2003AdultsNZA lozenge; 13.3 mg every 2–3 h while awake< 24Until symptom resolution1 d after symptom resolutionResolution of all or all but one mild symptom*George and Patsy Eby Research Foundation, NIH
Smith et al., 198938United States174Jan 1986–May 1986AdultsNZG lozenge; loading dose 46 mg, then 23 mg every 2 h while awakeNR7 d or until symptom resolution7 dResolution of 11 symptoms (10 listed* plus chilliness)Pharma (McNeil Consumer Products)
Turner et al. (A), 200024United States273NRAdults, age 18–65 yrIZG or ZA lozenge; ZG 13.3 mg, or ZA 11.5 mg or 5 mg; every 2–3 h (total 6/d)< 48Until symptom resolution (minimum 3 d, maximum 14 d)14 d2 consecutive symptom scores ≤ 1‡Pharma (Warner Lambert Consumer)
Turner et al. (B), 200024United States281NRAdults, age 18–65 yrNZG or ZA lozenge; ZG 13.3 mg, or ZA 11.5 mg or 5 mg; every 2–3 h (total 6/d)< 36Until symptom resolution (minimum 3 d, maximum 14 d)14 d2 consecutive symptom scores ≤ 1‡Pharma (Warner Lambert Consumer)
Weismann et al., 199039Denmark145Feb 1987–Feb 1988Adults, age 18–65 yrNZG lozenge; 4.5 mg every 1–1.5 h while awake (10 daily)< 24Until symptom resolution (maximum 10 d)10 dAbsence of 9 symptoms (10 listed* plus indisposition and excluding sneezing and scratchy throat)Pharma (Kirsten B Staehr)

  • Note: NR = not reported, N = natural, I = induced, ZG = zinc gluconate, ZA = zinc acetate, ZS = zinc sulfate, SR = symptom resolution.

  • ↵* Headache, fever, muscle pain, sneezing, nasal drainage, nasal obstruction, sore throat, scratchy throat, cough and hoarseness.

  • ↵† Symptom score: 0 = none, 1 = mild, 2 = moderate, 3 = severe for 10 cold symptoms.*

  • ↵‡ Symptom score: 0 = none, 1 = mild, 2 = moderate, 3 = severe, 4 = very severe for 7 cold symptoms (sneezing, rhinorrhea, nasal obstruction, sore throat, cough, headache and hoarseness).