Colds Chapter PDF

**Colds** A *cold*, also known as the common cold, is a viral infection of the upper respiratory tract. According to some estimates, 1 billion cases of the common cold occur annually, making it one of the top five illnesses diagnosed in the United States.^[**1**](https://pharmacylibrary.com/doi/10....

**Colds** A *cold*, also known as the common cold, is a viral infection of the upper respiratory tract. According to some estimates, 1 billion cases of the common cold occur annually, making it one of the top five illnesses diagnosed in the United States.^[**1**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B1),[**2**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B2)^ Adults usually have 2--3 colds per year, whereas preschool children may experience 6 or more.[**^2^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B2) Colds may occur at any time of the year, but the incidence tends to be higher in winter months.[**^2^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B2) In the United States, colds constitute the leading cause of work and school absenteeism. A cold is usually a self-limiting illness; however, because symptoms are bothersome, patients frequently self-medicate, with an estimated \$11 billion spent annually on nonprescription cold and cough products.[**^3^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B3) **Pathophysiology of Colds** More than 200 viruses cause colds. Most colds in children and adults are caused by rhinoviruses, a group of RNA viruses with more than 100 known serotypes.^[**1**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B1),[**2**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B2)^ Other viruses known to cause colds include coronaviruses, parainfluenza, respiratory syncytial virus, adenoviruses, and human metapneumovirus. In rare cases, some afflicted individuals may experience coinfection with bacteria (usually group A beta-hemolytic streptococci). During a cold, the viral infection is limited to the upper respiratory tract and primarily affects the pharynx, nasopharynx, nose, cavernous sinusoids, and paranasal sinuses. The respiratory tract's intricate host defense system usually protects the body from infectious and foreign particles. The respiratory tract, especially the nose, is well perfused by blood vessels and well innervated by sensory, cholinergic, and sympathetic nerves. Upon stimulation by an infectious (e.g., a cold) or allergic (e.g., allergic rhinitis) process, nasal nerves play a role in the resulting symptoms and thus serve as targets for some nonprescription therapies. For example, sneezing is caused by stimulation of sensory fibers by mechanical and thermal stimuli or by mediators such as histamine and bradykinin, while cholinergic and sympathetic nerves that innervate glands and their arteries play a role in congestion. Cholinergic stimulation dilates arterial blood flow, which results in congestion, whereas sympathetic stimulation constricts arterial blood flow to reduce congestion. Nasal sensory, cholinergic, and sympathetic nerves involved in cold symptoms are responsive to a variety of neuropeptide neurotransmitters that modulate their activity. A cold develops after a rhinovirus (or similar virus) binds to glycoprotein receptors, such as intercellular adhesion molecule-1, on respiratory epithelial cells in the nose and nasopharynx.[**^4^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B4) Once inside an epithelial cell, the virus replicates and infection spreads to other cells.[**^4^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B4) Peak viral concentrations are achieved 2--4 days after the initial inoculation, and viruses are present in the nasopharynx for 16--18 days.[**^1^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B1) Infected cells release chemokine "distress signals," and cytokines then activate inflammatory mediators and neurogenic reflexes. These activation processes result in recruitment of additional inflammatory mediators, vasodilation, transudation of plasma, glandular secretion, and stimulation of pain nerve fibers and sneeze and cough reflexes. Inflammatory mediators and parasympathetic nervous system reflex mechanisms cause hypersecretion of watery nasal fluid. Viral infection ends when a sufficient amount of a neutralizing antibody (secretory immunoglobulin A \[IgA\] or serum IgG) leaks into the mucosa to end viral replication. The most efficient mode of viral transmission is self-inoculation of the nasal mucosa or conjunctiva after contact with virus-laden secretions, which are typically present on the hands, but also may be found on inanimate objects (e.g., doorknobs, telephones). Transmission by means of inhalation of aerosolized viral particles is also common. Increased susceptibility to colds has been linked to higher exposure rates (e.g., with increased population density in classrooms or day care centers); allergic disorders affecting the nose or pharynx; limited social networks that restrict exposure to pathogens; and a weakened immune system secondary to smoking, a sedentary lifestyle, chronic (i.e., ≥1 month) psychological stress, or sleep deprivation (e.g., poor sleep quality or \101.5^°^F (38.6^°^C), tooth pain, halitosis, upper respiratory tract symptoms for \>7 days with poor response to decongestants West Nile virus infection Fever, headache, fatigue, rash, swollen lymph glands, and eye pain initially, possibly progressing to gastrointestinal distress, CNS changes, seizures, or paralysis Whooping cough Initial catarrhal phase (rhinorrhea, mild cough, sneezing) of 1--2 weeks, followed by 1--6 weeks of paroxysmal coughing Key: T, temperature. Most infected individuals do not experience complications from colds. Potential complications that may result from colds include sinusitis, otitis media (Otic Disorders), bronchitis, pneumonia, and exacerbation of asthma or chronic obstructive pulmonary disease. **Decision Tree: Common Cold** **Figure 1: Self-care for the common cold. Key: AH, antihistamine; AIDS, acquired immunodeficiency syndrome; CAM, complementary and alternative medicine; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; OTC, over-the-counter.** **Treatment of Colds** ***Treatment Goals*** Because there is no known cure for colds, the goal of therapy is to reduce bothersome symptoms while preventing transmission of cold viruses to other persons. ***General Treatment Approach*** Antibiotics are ineffective against viral infections, and the mainstay of cold treatment is nonpharmacologic therapy. If the patient desires to self-treat, a stepwise approach using single-entity products targeting specific symptoms is preferred over the use of combination products ([Figure 1](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#F1)), because symptoms appear, peak, and resolve at different times.[**^4^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B4) Patient education regarding the administration of intranasal drugs ([**Table 2**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#T2)) and ophthalmic preparations (see [Ophthalmic Disorders](http://pharmacylibrary.com/doi/full/10.21019/aphaotc-ophthal.ophthalmic-disorders)) is an important component of management. Not all patients should self-treat for a cold (see the exclusions for self-treatment listed in [Figure 1](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#F1)). +-----------------------------------+-----------------------------------+ | **Table 2: Administration | | | Guidelines for Nasal Dosage | | | Formulations** | | +===================================+===================================+ | **General Instructions** | | +-----------------------------------+-----------------------------------+ | - Clear nasal passages before | | | administering the product. | | | | | | - Wash your hands before and | | | after use. | | | | | | - Gently depress the other side | | | of the nose with finger to | | | close off the nostril not | | | receiving the medication. | | | | | | - Aim tip of delivery device | | | away from nasal septum to | | | avoid accidental damage to | | | the septum. | | | | | | - Breathe through mouth and | | | wait a few minutes after | | | using the medication before | | | blowing the nose. | | +-----------------------------------+-----------------------------------+ | **Nasal Sprays** | **Nasal Inhalers** | | | | | - Gently insert the bottle tip | - Warm the inhaler in hand just | | into one nostril, as shown in | before use. | | drawing A. | | | | - Gently insert the inhaler tip | | - Keep head upright. Sniff | into one nostril, as shown in | | deeply while squeezing the | drawing C. Sniff deeply while | | bottle. Repeat with other | inhaling. | | nostril. | | | | - Wipe the inhaler after each | | | use. Discard after 2--3 | | | months even if the inhaler | | | still smells medicinal. | | | | | |  | +-----------------------------------+-----------------------------------+ | **Pump Nasal Sprays** | **Nasal Drops** | | | | | - Prime the pump before using | - Lie on bed with head tilted | | it the first time. Hold the | back and over the side of the | | bottle with the nozzle placed | bed, as shown in drawing D. | | between the first two fingers | | | and the thumb placed on the | - Squeeze the bulb to withdraw | | bottom of the bottle. | medication from the bottle. | | | | | - Tilt the head forward. | - Place the recommended number | | | of drops into one nostril. | | - Gently insert the nozzle tip | Gently tilt head from side to | | into one nostril, as shown in | side. | | drawing B. Sniff deeply while | | | depressing the pump once. | - Repeat with other nostril. | | | Lie on bed for 1--2 minutes | | - Repeat with other nostril. | after placing drops in the | | | nose. | | | | | | - Do not rinse the dropper. | | | | | |  | +-----------------------------------+-----------------------------------+ Note: Do not share the drug or its dispenser with anyone. Discard solutions if discolored or if contamination is suspected. Remove caps before use and replace tightly after each use. Do not use expired products. ***Nonpharmacologic Therapy*** Although evidence of efficacy is lacking, popular therapeutic measures include increased fluid intake, adequate rest, a nutritious diet as tolerated, and increased humidification with steamy showers, vaporizers, or humidifiers. Vaporizers heat water to produce steam and can deliver medications such as Vicks VapoSteam (camphor 6.2%). By contrast, humidifiers use fans or ultrasonic technology to produce a cool mist and cannot accommodate liquid additives. Saline-lubricant nasal sprays or drops moisten irritated mucosal membranes and loosen encrusted mucus; salt gargles may ease sore throats. Hot tea with lemon and honey, chicken soup, and vegetable and other broths are soothing. Limited evidence suggests that several substances in chicken soup could have anti-inflammatory activity.[**^8^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B8) Milk products should not be withheld, in view of the lack of evidence that milk increases cough or congestion. Medical devices such as Breathe Right nasal strips are marketed for temporary relief from nasal congestion and stuffiness resulting from colds and allergies. Those devices lift the nares open, thereby enlarging the anterior nasal passages. Aromatic oils (e.g., camphor, menthol, eucalyptus) contained in products such as Vicks VapoRub (for patients 2 years and older) ease nasal congestion and improve sleep by producing a soothing sensation.[**^9^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B9) Children should be supervised closely when these products are used because aromatic oils can irritate the eyes and skin, and extensive exposure through inhalation or accidental ingestion can lead to toxicity. Nondrug therapy for all patients, especially for infants, includes upright positioning to enhance nasal drainage. Because children typically cannot blow their own noses until the age of approximately 4 years, carefully clearing the nasal passageways with a nasal aspirator (e.g., bulb syringe, NoseFrida) may be necessary if accumulation of mucus interferes with sleeping or eating. Nasal aspirators may be electronically, mechanically, or manually operated. To use a bulb syringe manually and avoid harm to the child, the caregiver should squeeze the large end of the bulb *before* inserting it, continue this compression while gently inserting the tip into the infant's nose, and then slowly release the squeezing pressure to draw out fluid. After the pressure is completely released, the syringe is removed from the infant's nose and the fluid expelled from the syringe by again compressing the bulb. By contrast, caregivers can use oral suction to remove mucus by placing a device (e.g., NoseFrida SnotSucker) against the child's nostril or use an electronic motorized suction device, which is gently inserted into the child's nostril. Proper hand hygiene reduces the transmission of cold viruses. The Centers for Disease Control and Prevention (CDC) encourages frequent hand cleansing with soap or soap substitutes such as hand sanitizers.[**^2^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B2) Not all hand sanitizers are effective at eradicating rhinoviruses from the skin. In a review of the safety and effectiveness of consumer and health care antiseptics, the U.S. Food and Drug Administration (FDA) determined that only 3 ingredients were eligible to be marketed in consumer antiseptic rubs: benzalkonium chloride, alcohol (ethyl alcohol or ethanol, 60%--95%), and isopropyl alcohol (70%--91.3%).[**^10^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B10) FDA also determined that 28 ingredients, including chlorhexidine gluconate, iodine complex, and triclosan, were ineligible. Alcohol-based nasal sanitizers (e.g., Nozin) are available, but evidence of their efficacy against cold viruses is lacking. Use of antiviral disinfectants such as Lysol to clean surfaces (which kills \>99% of rhinoviruses after contact for 1 minute) and antiviral tissues such as Kleenex Anti-Viral (incorporating a tissue layer containing citric acid and sodium lauryl sulfate) also may help prevent transmission of viruses. **Pharmacologic Therapy** ***Decongestants*** Decongestants are adrenergic agonists (sympathomimetics) used to specifically treat sinus and nasal congestion. Stimulation of alpha-adrenergic receptors constricts blood vessels, thereby decreasing sinusoid vessel engorgement and mucosal edema. Three types of decongestants are available: direct-acting, indirect-acting, and mixed. *Direct-acting* decongestants (e.g., phenylephrine, oxymetazoline, tetrahydrozoline) bind directly to adrenergic receptors. *Indirect-acting* decongestants (e.g., ephedrine) displace norepinephrine from storage vesicles in prejunctional nerve terminals, and tachyphylaxis can develop as stored neurotransmitter is depleted. *Mixed* decongestants (e.g., pseudoephedrine) have both direct and indirect activity. Systemic nonprescription decongestants include pseudoephedrine and phenylephrine. Intranasal nonprescription decongestants include the short-acting decongestants ephedrine, levmetamfetamine (L-desoxyephedrine), naphazoline, phenylephrine, and propylhexedrine, as well as the long-acting decongestants xylometazoline (8--10 hours) and oxymetazoline (12 hours). Ophthalmic nonprescription decongestants are also available (see [Ophthalmic Disorders](http://pharmacylibrary.com/doi/full/10.21019/aphaotc-ophthal.ophthalmic-disorders)). Systemic decongestants are rapidly metabolized by monoamine oxidase (MAO) and catechol-*O*-methyltransferase in the gastrointestinal (GI) mucosa, liver, and other tissues. Pseudoephedrine is absorbed well after oral administration; phenylephrine has a low oral bioavailability (approximately 38%). Both pseudoephedrine and phenylephrine have short half-lives (pseudoephedrine: 6 hours; phenylephrine: 2.5 hours), and peak concentrations for both drugs are reached at 0.5--2 hours after oral administration. Decongestants are indicated for temporary relief of nasal and Eustachian tube congestion and for cough associated with postnasal drip. Nonprescription decongestants are not approved by FDA to self-treat nasal congestion associated with sinusitis. FDA-approved dosages for decongestants are listed in **[Tables 3](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#T3)[^11^](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B11)**^,[**12**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B12)^ and [**4**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#T4).[**^11^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B11) (*Note*: In 2008, manufacturers voluntarily updated cough and cold products labels to state "do not use" in children under 4 years old.[**^13^**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#B13)) Nonprescription decongestants are marketed in a variety of dosage formulations, and many combination products are available ([**Table 5**](https://pharmacylibrary.com/doi/10.21019/aphaotc-resp.colds-allergy#T5)). **Table 3: Dosage Guidelines for Nonprescription Systemic Nasal Decongestants** --------------------------------------------------------------------------------- -------------------------------------- --------------------------------- ------------------------------------------------------------------- ** ** **Dosage^a^ (maximum daily dosage)** **Drug** **Adults and Children \>12 Years** **Children 6 to ≤12 Years** **Children 2 to \