Treating the Common Cold
The common cold is a viral upper respiratory infection (URI) and is the leading cause of missed work and school days.1,2 Adults experience between 2 and 4 colds per year, and children have between 6 and 10 per year.2 The common cold is self-limiting and generally does not cause serious health conditions in otherwise healthy individuals.1,3 Otitis media has been reported to occur in 20% of children who are infected with the common cold.3,4
The common cold can be caused by 1 of >200 viruses.1,2 The most common virus is the rhinovirus, which has >100 different subtypes and causes 30% to 40% of colds.1,2,5 Other common viruses that cause colds include coronavirus, parainfluenza virus, respiratory syncytial virus, adenovirus, and enterovirus.2,4,5 Colds are transmitted by inhalation or self-inoculation with infected respiratory secretions.6
Presentation of Symptoms
Symptoms of the common cold may develop 1 to 3 days after exposure to the virus, and they generally last for 1 to 2 weeks.1,2,6 The chronology of symptoms is important and fairly consistent. A sore throat usually is the first symptom, and, although it can be severe, it resolves quickly.1,3 By day 2 or 3, nasal symptoms dominate; these symptoms include nasal congestion, drainage, and postnasal drip. A cough may present on day 4 or 5, although cough occurs in only 20% of patients.1
Due to an overlap of presenting symptoms, it is often difficult to differentiate between the common cold and influenza (flu). Patients with the flu present with more severe and unique symptoms, including fever, headache, fatigue, and exhaustion. Nasal congestion, sneezing, and sore throat almost always are present with the common cold but are seen less often with the flu.7
Frequent hand washing is recommended to prevent transmission. Because the rhinovirus can live on skin and objects for up to 3 hours, disinfectants should be used to clean all contaminated surfaces.2 Antiviral tissues can be recommended. They are effective in killing rhinovirus, influenza virus, and respiratory syncytial virus within 15 minutes of contact with the tissue.1,8
Pharmacologic Management of Symptoms
Treatment is targeted at reducing the severity of symptoms, and some homeopathic medications may decrease the duration of symptoms. When selecting OTC cold preparations, patients should be advised to take only products that contain ingredients to treat the symptoms they are experiencing.1
Decongestants are sympathomimetics that induce vasoconstriction of blood vessels in the nasal mucosa that are dilated during a cold.9,10 Systemic decongestants can cause increases in heart rate and blood pressure. The stimulating effects of decongestants may result in anxiety, insomnia, nervousness, and restlessness. Decongestants should be used with caution in patients who have hypertension, arrhythmias, diabetes mellitus, glaucoma, hyperthyroidism, ischemic or coronary heart disease, and benign prostatic hypertrophy (BPH). Systemic decongestants are contraindicated if taken concurrently with or within 14 days of stopping a monoamine oxidase inhibitor (MAOI) because of the risk of hypertensive emergencies.9
Topical decongestants offer the advantage of quick relief. The disadvantage of topical decongestants is that when they are used for longer than 3 to 5 days they can cause rhinitis medicamentosa, or rebound congestion.1,10,11 Additional local side effects include burning, stinging, sneezing, and dryness.10,11 Topical decongestants are minimally absorbed; however, systemic side effects of oral decongestants may be observed.10
First-generation, sedating antihistamines are effective in the treatment of sneezing and rhinorrhea associated with the common cold.1,12 Second-generation, nonsedating antihistamines are not effective in treating symptoms of the common cold.12
Drowsiness is the most predominant central nervous system effect found with first-generation antihistamines, although it varies among the OTC antihistamines; chlorpheniramine and brompheniramine produce less sedation than clemastine and diphenhydramine.10 First-generation antihistamines also cause more anticholinergic effects, including dry mouth, nose, and throat; blurred vision; urinary retention; constipation; and tachycardia. Gastrointestinal side effects also can occur, including loss of appetite, nausea, and vomiting.10 Patients who have glaucoma, hyperthyroidism, BPH, and cardiovascular disease should consult their pharmacist or physician before using antihistamines.12 When MAOIs are combined with first-generation antihistamines, anticholinergic effects can be intensified.1
Cough Suppressants and Expectorants
Dextromethorphan and codeine are antitussive agents used in the treatment of a nonproductive cough or a productive cough that may be interfering with sleep. These agents usually are well-tolerated but may cause mild dizziness, fatigue, and drowsiness. Dextromethorphan is contraindicated in patients who are currently taking or have stopped an MAOI within the past 14 days. Concurrent use of dextromethorphan and MAOIs can result in serotonin syndrome. Because dextromethorphan is metabolized by the cytochrome P-450 2D6 enzyme, the dose of dextromethorphan should be decreased when it is used in combination with 2D6 inhibitors (such as fluoxetine and paroxetine).13
In some states, codeine is available as an OTC cough medication. Codeine has significant side effects, including sedation, constipation, and nausea. More serious but rare side effects with doses used for cough include respiratory depression, seizures, and physical dependence.14
Guaifenesin is an expectorant that is indicated in the treatment of a productive cough. It decreases the viscosity of newly forming respiratory secretions. Guaifenesin is not recommended for the treatment of chronic coughs associated with smoking, emphysema, asthma, and chronic bronchitis. It generally is well-tolerated, but nausea, vomiting, and stomach discomfort can occur. There are no known drug interactions with guaifenesin.15
The American College of Chest Physicians clinical practice guidelines16,17 do not recommend the use of central or peripherally acting cough suppressants in coughs associated with URIs because of their limited efficacy. It is recommended that patients experiencing a cough associated with the common cold or postnasal drip associated with a URI use a first-generation antihistamine and a decongestant to treat cough. As with the treatment of sneezing associated with the common cold, second-generation antihistamines are not effective in the treatment of cough and should not be recommended.
Zinc. Although there is no "cure" for the common cold, zinc products have been widely touted and used by patients to prevent or reduce the duration of the common cold. Zinc is thought to work by blocking the rhinovirus from binding to its receptor in nasal epithelium cells.18 Patients should be told to start zinc within 24 to 48 hours of the onset of symptoms. Some product packaging may recommend continuing the zinc product for 48 hours after symptoms resolve to achieve maximum benefit.19
Clinical trials involving zinc have reported inconsistent results. A meta-analysis20 evaluating the efficacy of zinc lozenges concluded that strong evidence of efficacy is not present. Other trials and a review article, however, have reported some benefit in reducing the duration of a cold.21-23 Three studies22-24 have been conducted with zinc gluconate nasal gel spray. Two studies showed a positive result, with an improvement in the duration of symptoms.22,23
Oral zinc may cause taste alterations or a metallic taste.25 Intranasal zinc can cause epistaxis, burning, stinging, dry nasal mucus membranes, and throat and nasal irritation.18,25 Cases of anosmia (loss of the sense of smell) have recently been reported.26 Patients should be counseled not to sniff deeply when applying zinc nasally. Anosmia has not been reported in past clinical trials involving intranasal zinc gluconate, but further evaluation of the prevalence of this possible side effect is warranted.
Oral zinc can result in decreased bioavailability of certain drugs. Drug interactions involving zinc and antibiotics, specifically quinolone and tetracyclines, apply to zinc products that are absorbed orally. These drugs form complexes with zinc in the GI tract and require separation by taking the antibiotics 2 hours before or 4 to 6 hours after taking oral zinc supplements.25
Echinacea. Echinacea is an herbal plant used in infections because of its potential immune-stimulating properties. Echinacea purpurea, E angustifolia, and E pallida are the various species used in preparations marketed as containing echinacea.27,28 Echinacea should not be recommended for use for more than 8 weeks.27,29 When using echinacea for the treatment of the common cold, it should be started at the onset of symptoms and continued for 7 to 10 days.27,28
Echinacea has been studied for the prevention and treatment of the common cold, and conflicting study results have been reported in the literature. Although some studies have shown some effectiveness for treatment, benefits for prevention have not been shown.27,30,31 Studies and reviews on the treatment of the common cold with echinacea tend to show limited to no benefit.27-29,31
Echinacea should be avoided by patients who are allergic to flowers in the Asteraceae (or Compositae) family (ie, ragweed, chrysanthemums, marigolds, and daisies) because of the risk of hypersensitivity reactions.27 Echinacea should be avoided by patients who have immunodeficiencies or autoimmune diseases. GI side effects of echinacea include nausea, vomiting, diarrhea, and stomach pain.27,32 Due to the immune-stimulating properties of echinacea, concurrent use with immunosuppressive medications should be avoided.32
Vitamin C is thought to enhance immune system function and has been used to prevent or treat the common cold.33 A meta-analysis34 evaluated 55 studies that were conducted starting in 1942. The authors concluded that the evidence reviewed was not strong enough to support the general use of high-dose vitamin C to prevent the common cold.
Common side effects that can occur with vitamin C supplementation include nausea, vomiting, heartburn, diarrhea, and headache. Side effects tend to be dose-related, and high doses of vitamin C of >2 g per day are not recommended because of increased side effects such as severe diarrhea. In addition, kidney stones can be formed at higher doses.33
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6. The common cold. American Lung Association. 2006. Available at: www.lungusa.org/site/pp.aspx?c=dvLUK9O0E&b=35873&printmode=1.
7. National Institute of Allergy and Infectious Disease. Is it a cold or the flu? 2006. Available at: www.niaid.nih.gov/publications/cold/sick.pdf.
8. Kleenex Brand Anti-Viral Tissue. 2006.
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23. Mossad SB. Effect of zincum gluconicum nasal gel on the duration and symptom severity of the common cold in otherwise healthy adults. QJM. 2003;96(1):35-43.
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