DRUGS FOR ALLERGIC RHINITIS, COUGH, AND COLDS

Pharmacology Lab

Allergic Rhinitis

Allergic rhinitis is an inflammatory disorder that affects the upper airway, lower airway, and eyes.

Symptoms are triggered by airborne allergens, which bind to IgE antibodies on mast cells and thereby cause release of inflammatory mediators, including histamine, leukotrienes, and prostaglandins.

Allergic rhinitis is the most common allergic disorder, affecting 15% to 20% of the U.S. population.

Drugs Used

Antihistamines Oral antihistamines—H1-receptor antagonists

most commonly prescribed for allergic rhinitis do not decrease nasal congestion; no value for

cold treatment best when taken prophylactically, so administer

on regular basis throughout allergy season adverse effects mild, such as dry mouth,

constipation, or urinary hesitancy (sedation with first-generation drugs such as diphenhydramine)

Azelastine nasal spray (Astelin) Only antihistamine available for

intranasal use via metered spray device Bitter taste is common side effect 12% experience somnolence

Intranasal Glucocorticoids

Actions and uses—Most effective drugs for seasonal and perennial rhinitis; prevent or suppress major symptoms of allergic rhinitis; used for those that cannot be controlled with conventional drugs; may replace or join H1-receptor antagonists as first-line therapy

Intranasal Glucocorticoids: Continued Adverse effects—Mild (drying of nasal

mucosa and sensations of burning or itching); could get adrenocortical suppression

Preparations, dosage, and administration—Use metered spray device; give full doses initially then reduce to lowest effective dose; may need a week or more to develop benefits; maximum benefits in 2 to 3 weeks

Intranasal Cromolyn Sodium

Actions and uses—Safe and effective to relieve symptoms; no benefit for nonallergic rhinitis; acts on mast cells to suppress release of histamine and other mediators; take before onset of symptoms; takes about a week to develop beneficial effects

Intranasal Cromolyn Sodium: Continued Dosage and administration

(NasalCrom)—Administered with metered spray device; for children over 6 years and adults; one spray (5.2 mg) per nostril 4 to 6 times/day; use topical decongestant before cromolyn if nasal congestion present; use on regular schedule throughout allergy season

Sympathomimetics (Decongestants) Actions and uses—Examples

(phenylephrine) act by stimulating alpha1-adrenergic receptors on smooth muscle of nasal blood vessels vasoconstriction and decreased nasal drainage; topical administration is rapid and intense compared with oral decongestants

Sympathomimetics (Decongestants): Continued Adverse Effects: Rebound congestion

—Develops when topical decongestants are administered on regular basis for extended time; can become a cycle; need to discontinue drug or use in one nostril at a time or use no more than 3 to 5 days; not for chronic rhinitis

Cough

Cough is complex reflex involving CNS, peripheral nervous system, and muscles of respiration; should not suppress productive cough; otherwise, antitussive medication is appropriate

Antitussives

Suppress cough by acting within CNS or peripherally; two groups

Opioid antitussives—All opioid analgesics have ability to suppress cough; usually use codeine or hydrocodone, which act in CNS; hydrocodone more potent, so increased risk for abuse; codeine most effective to decrease frequency and intensity of cough; use 10 to 20 mg four to six times daily; not usually used for children

Nonopioid Antitussives

Dextromethorphan—Most effective; acts in CNS; a derivative of opioids; does not produce analgesia, euphoria, or physical dependence; usual dosage is 10 to 30 mg every 4 to 8 hours; adverse effects mild

Other nonopioid antitussives—Diphenhydramine can also suppress cough with sedative and anticholinergic properties; benzonatate is analogue of tetracaine and is thought to suppress cough by decreasing sensitivity of respiratory tract stretch receptors; mild adverse effects; swallow capsule intact

Expectorants and mucolytics Expectorants make cough more

productive; mucolytics make it more watery

Acute Upper Respiratory Infection Of viral origin

fever common in children but rare in adults; no cure; treat symptoms

do not use antibacterial drugs unless a bacterial infection follows

no evidence that vitamin C prevents or helps cold

treat with drug for specific symptoms, not multiple mixtures for single symptoms

Upper Respiratory Infection

combination drugs usually include a nasal decongestant, an antitussive, an analgesic, an antihistamine, and caffeine

antihistamine only for its anticholinergic effect and caffeine to offset sedative effects of antihistamine

disadvantages include either over or undermedicating with one or more of the combinations

Critical Thinking

You are doing a clinical rotation in a family practice setting. You have been assigned to follow Ms. K through her visit to the primary care provider. As you complete your interview with Ms. K, she asks whether you can answer some questions.

 She says, “I have a lot of stuffiness with my nose. I’m not sure whether I want to take anything for it because my friend told me that she started to take a medication that was a decongestant spray, and now she can’t stop taking it. Do you know anything about this?” How should you reply?

 She then asks, “Can anything be done to prevent dependency on a decongestant spray?” How should you respond?

Response

1. You can tell Ms. K that decongestants can be used to reduce nasal congestion. They work by causing the blood vessels of the nose to constrict, which results in shrinkage of the swollen nasal membranes. When nasal sprays are used for more than a few days, the effects of each application wear off, and the congestion becomes more severe. To overcome the rebound congestion, the patient must use progressively larger and more frequent doses. Hence a cycle can develop. To break the cycle, use of the decongestant can be discontinued abruptly. This is very uncomfortable for the patient. The discomfort can be lessened by discontinuing use of the drug in one nostril at a time.

2. You can tell Ms. K that rebound congestion can be minimized by use of topical agents for 3 to 5 days.

Questions 1

The principle drugs used to treat allergic rhinitis include: oral antihistamines intranasal glucocorticoids intranasal cromolyn sympathomimetics

Question 2

What is the role of antihistamines in the treatment of the common cold? Antihistamines are of no value

against the common cold because they do not reduce nasal congestion.

Question 3

What is the role of antihistamines in the treatment of allergic rhinitis? They can relieve sneezing, rhinorrhea, and

nasal itching. Antihistamines are most effective when taken prophylactically and less helpful when taken after symptoms have appeared. Therefore they should be administered on a regular basis throughout the allergy season, even when symptoms are absent.

Question 4

What is the only antihistamine available for intranasal use? Azelastine

Question 5

How does cromolyn work? Cromolyn reduces symptoms by suppressing the release of histamine and other inflammatory mediators from mast cells.

Question 6

What drug is a monoclonal antibody that is directed against immunoglobulin E (IgE) omalizumab

Question 7

The two most frequently drugs used for cough suppression are? Codeine hydrocodone

Question 8

What is the most effective nonopiod cough suppressant available? Dextromethorphan