Chapter 72 - Drugs For Allergic Rhinitis, Cough, And Colds

CHAPTER 72 I.

DRUGS

FOR

DRUGS

FOR

ALLERGIC RHINITIS, COUGH,

AND

COLDS

ALLERGIC RHINITIS

- an inflammatory disorder that affects the upper airway, lower airway,

and eyes - symptoms are sneezing, rhinorrhea (runny nose), pruritus (itching) and nasal congestion (caused by dilation of nasal blood vessels) Forms:

seasonal – also known as hay fever or rose fever - occurs in the spring and fall in reaction to outdoor allergens,

including fungi and pollens from weeds, grasses, and trees perennial – (nonseasonal) triggered by indoor allergens, especially the house dust mite and pet dander A.

ANTIHISTAMINES 1. Oral – first line drugs for allergic rhinitis - can relieve sneezing, rhinorrhea, and nasal itching - do not reduce nasal congestion - no value against the common cold - most effective if taken prophylactically, even when symptoms are absent - sedation is the most common adverse effect - anticholinergic effects (dry mouth, constipation, urinary hesitancy) may occur What is the role of antihistamines in the treatment of the common cold? What is the role of antihistamines in the treatment of allergic rhinitis?

B.

2.

Azelastine (trade name: Astelin) Nasal Spray - only antihistamine available for intranasal use - dispensed in a metered spray device - usual dosage is two sprays in each nostril twice daily - bitter taste in the mouth is the most common side effect

3.

OTC – Benadryl, Chlor-Trimenton - sedation is a problem with these agents - Claritin, Claritin D now OTC – less sedating - prescription = Clarinex, Zyrtec, Allegra

INTRANASAL GLUCOCORTICOIDS - Flonase, Beconase, Nasonex, Nasolide - most effective drugs for treating seasonal and perennial rhinitis - over 90% of patients respond

- because of their anti-inflammatory actions, can prevent or suppress all of the major symptoms of allergic rhinitis (congestion, rhinorrhea, sneezing, nasal itching, and erythema) - now considered a first-line therapy drug - administered using a metered spray device - for seasonal allergic rhinitis - - maximal effects may require a week or more to develop - for perennial rhinitis - - maximal responses may take 2 – 3 weeks to develop - if nasal passages are blocked, they should be cleared with a topical decongestant prior to glucocorticoid administration Adverse Effects: generally mild, include drying of the nasal mucosa and burning or itching sensation - caused by the vehicle employed for administration and not by the steroids themselves - aqueous vehicles are much less irritating than non-aqueous C.

INTRANASAL CROMOLYN SODIUM (TRADE NAME: NASALCROM) - used to both prevent and treat allergic rhinitis - very safe and effective - reduces symptoms by suppressing release of histamine and other inflammatory mediators from mast cells - most effective when taken prior to onset of symptoms - beneficial effects may take a week or two to develop - administered with a metered spray device - if nasal congestion is present, a topical decongestant should be used prior to administering cromolyn What are the principle drugs used to treat allergic rhinitis? D.

SYMPATHOMIMETICS (DECONGESTANTS) - phenylephrine - reduces nasal congestion by stimulating alpha1-adrenergic receptors on nasal blood vessels, causing vasoconstriction, in turn causing shrinkage of swollen membranes followed by nasal drainage - topical administration vasoconstriction is both rapid and intense - oral administration responses are delayed, moderate and prolonged - only relieves stuffiness in allergic rhinitis patients - do not reduce rhinorrhea, sneezing or itching Adverse Effects: rebound congestion – develops when topical agents are used more than a few days

- with prolonged use, the effects of each application wears off and congestion becomes progressively more severe - to overcome this condition, the patient must use progressively larger and more frequent doses - to break this cycle of escalating congestion and increased drug use, abrupt decongestant withdrawal will work but is extremely uncomfortable - less drastic approach is to discontinue drug use in one nostril at a time - can be minimized by limiting use of topical agents to 3 – 5 days CNS Stimulation – most common - symptoms include restlessness, irritability, anxiety, and insomnia Cardiovascular Effects – for individuals with HTN or coronary artery disease, widespread vasoconstriction can be hazardous - generalized vasoconstriction is most likely with oral agents Hemorrhagic Stroke – phenylpropanolamine was removed from the market because it was shown to cause subarachnoid and intracerebral hemorrhage in women (but not in men) - unknown if other alpha agonists (phenylephrine, ephedrine, pseudoephrine) also pose a risk of hemorrhagic stroke

Abuse – by causing CNS stimulation, can produce subjective effects similar to those of amphetamine, subject to abuse - employed as decongestants, abuse is most common with pseudoephedrine and ephedrine (sold as Sudafed, for example) - although these agents are available without prescription and are not regulated under the Controlled Substances Act, pharmacies are beginning to keep them behind the counter so as to hamper inappropriate use

II.

DRUGS

FOR

COUGH

- cough is often beneficial, serving to remove foreign matter and excess secretions from the bronchial

tree - productive cough is characteristic of chronic lung disease (emphysema, asthma, bronchitis) and should not be suppressed - not all cough is useful, frequently serves only to deprive us of comfort or sleep A.

ANTITUSSIVES - drugs that suppress cough 1.

Opioid Antitussives – codeine and hydrocodone - act in the CNS to elevate cough threshold - hydrocodone is somewhat more potent than codeine and carries a greater liability for abuse a.

Codeine – most effective cough suppressant - active orally and can decrease both the frequency and intensity of cough - doses are low, about one-tenth those needed to relieve pain - risk of physical dependence is small - can suppress respiration - in the event of overdose, respiratory depression may prove fatal - Narcan can be administrated to reverse overdose effects B.

NONOPIOID ANTITUSSIVES 1. Dextromethorphan – most effective nonopioid cough medicine - acts in the CNS - although a derivative of the opioids, it does not produce euphoria or physical dependence and lacks any potential for abuse - does not depress respiration 2.

Others – Diphenhydramine – mechanism of antitussive action is unclear - has sedative and anticholinergic properties - cough suppression is achieved only at doses that produces prominent sedation Benzonatate (tessalon perles) – structural analog of a local

anesthetic - dispensed in tiny yellow capsules which should be swallowed intact, since chewing will anesthetize the mouth and pharynx What are the most frequently used drugs for cough suppression? What is the most effective nonopiod cough suppressant available?

C.

EXPECTORANTS AND MUCOLYTICS 1. Expectorants – a drug that renders cough more productive by stimulating the flow of respiratory tract secretions - in almost all cases, efficacy is doubtful - guaifenesin (glyceryl guaiacolate) may be an exception to this rule 2. watery

Mucolytics – a drug that reacts directly with mucus to make it more

- this action helps make cough more productive - administered by in halation - can cause bronchospasm - because of its sulfur content, mucomyst has the additional drawback of smelling like rotten eggs - mucinex is a new drug OTC that is administered orally on a dosing schedule of Q12

III.

COLD REMEDIES: COMBINATION PREPARATIONS

- acute upper respiratory infection of viral origin - symptoms are rhinorrhea, nasal congestion, cough, sneezing, sore throat, hoarseness, headache, malaise, and myalgia; fever is common in children but rare in adults - no cure for the cold - because colds are caused by viruses, there is no justification for the routine use of antibacterial drugs - combination cold remedies should be reserved for patients with multiple symptoms - combination chosen should contain only those agents that are appropriate for the symptoms to be treated - combination cold remedies frequently contain two or more of the following: • nasal decongestant • antitussive • analgesic • antihistamine – included to suppress secretion of mucus • caffeine – added to offset sedative effects of antihistamine - brand-name product can be reformulated and the sold under the same name - without carefully reading the label, the consumer has no assurance that the brand name product purchased this year contains the same amounts of the same drugs that were present in last year’s version of that combination product