Respiratory: Decongestants Flashcards
Types of Respiratory Drugs:
Bronchodilators: Beta2-Receptor Agonists:
Basic Understanding:
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Decongestants are widely used for congestion associated with
the common cold and allergic rhinitis. Many preparations are
available without a prescription, and they are available in
many formulations. They come in liquid, tablet, capsule,
nasal spray, or drops, providing a variety of methods of administration. Although patients may self-treat with decongestants and the health-care provider may rarely prescribe
them, they are included here for the provider to learn about
the proper dosing and potential adverse effects or drug interactions that may occur with these medications.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacodynamics:
The decongestants are alpha-adrenergic–receptor agonists
(sympathomimetic) that produce vasoconstriction by stimulating alpha receptors within the mucosa of the respiratory
tract, which temporarily reduces the swelling associated with
inflammation of the mucous membranes. These sympathomimetic amines act on the alpha receptors of the vascular
smooth muscle, causing vasoconstriction, pressor effects, and
nasal decongestion. Other alpha effects include constriction of
the GI and urinary sphincters, mydriasis, and decreased pancreatic beta cell secretion. Pseudoephedrine (Sudafed), the
most commonly used systemic decongestant, is noted to have
mild CNS stimulant effects, especially in patients sensitive to
sympathomimetic drugs. Phenylpropanolamine, which was
often combined with an antihistamine in OTC cold medications, was removed from the market in 2005 after a public
health advisory found an increased risk for hemorrhagic stroke
in women. Other effects of the systemic decongestants are increased heart rate, force of contraction, and cardiac output.
These effects are usually mild in healthy patients, and at appropriate dosages, decongestion occurs without dramatic
blood pressure changes.
Pseudoephedrine is being replaced in some decongestant
products with phenylephrine hydrochloride to deter the
manufacture of methamphetamine, which uses pseudoephedrine as an ingredient. In 2006, the Combat Methamphetamine Epidemic Act was added to the USA Patriot Act.
The Combat act applies to all cough and cold products
(including combination products) that contain the methamphetamine precursor chemicals ephedrine, pseudoephedrine,
or phenylpropanolamine. The law includes a daily and
30-day limit on purchases of known methamphetamine precursors whether at a retail store or via the Internet. All potential precursors are to be stored behind the counter in retail
stores and retailers are required to ask for identification and
keep a log of who is purchasing the drugs. Some states
(Oregon) have made pseudoephedrine a Schedule III drug,
requiring a prescription to be written by a provider who is
licensed to prescribe controlled substances.
Topical decongestants are sympathomimetic amines that
cause intense vasoconstriction when applied directly to
swollen mucous membranes of the nasal passage. This
shrinks the swollen membranes, causing almost immediate
relief from nasal congestion. There are minimal systemic
effects from topical use of nasal decongestants.
What type of tissue do B2RAs act on?
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacokinetics: Absorption and Distribution:
The oral decongestants are well absorbed from the GI tract
and widely distributed. Pseudoephedrine is widely distributed and presumed to cross the blood–brain barrier and
placenta. Small amounts of pseudoephedrine are excreted in
breast milk. Absorption and distribution of the topical
decongestants have not been described.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacokinetics: Metabolism and Excretion:
Pseudoephedrine is partially metabolized in the liver into
norpseudoephedrine, an active metabolite. Pseudoephedrine
and its metabolite are excreted in the urine, with 50% to 75%
of the dose excreted as unchanged drug. Excretion of pseudoephedrine is highly dependent on the pH of the urine. If
the urine is acidic (pH near 5), the rate of urinary excretion
is increased. If the urine is alkaline (pH of 8), the rate of excretion is slowed, as some of the drug is reabsorbed into the
renal tubule.
Metabolism of phenylephrine is via the enzyme monoamine
oxidase in the liver. Excretion of phenylephrine or its metabolites has not been described. Metabolism and excretion of the
topical decongestants are not available.
Table 17-13 presents the pharmacokinetics of selected
decongestant.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacotherapeutics: Drug Interactions:
The MAOIs and beta-adrenergic blockers increase the effects
of sympathomimetics; therefore, patients taking these medications should avoid decongestants. Phenothiazines and
tricyclic antidepressants potentiate the pressor effects of pseudoephedrine. See Table 17-14 for further drug interactions.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacotherapeutics: Precautions and Contraindications:
There are only a few absolute contraindications to taking decongestants. The oral decongestants are absolutely contraindicated for patients on concurrent MAOI therapy. Concurrent
use of these medications may result in severe headache,
hypertension and hyperpyrexia, and possibly hypertensive
crisis. Oral decongestants are also contraindicated for patients
with severe hypertension or coronary artery disease.
Safety and efficacy of decongestant medications have been
questioned after a number of reports of deaths of infants
taking cold medications (Centers for Disease Control and
Prevention, 2007). In October 2007, an FDA panel met and
recommended all pediatric cough and cold medications be
relabeled as not indicated for use in children under age
4 years. In October 2007, manufacturers voluntarily removed
all infant drop formulas of cough and cold medications from
the market. After decongestants were relabeled in 2007, the
American Association of Poison Control Centers reported
54% fewer reports of therapeutic errors involving OTC cough
and cold medications in children younger than 2 years of age
(Klein-Schwartz, Sorkin, & Doyon, 2010).
Topical imidazolines (oxymetazoline) are to be used with
caution in children under age 6 years. Topical naphazoline is
contraindicated for patients with glaucoma.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacotherapeutics: Rational Drug Selection:
Topical Versus Systemic
Topical decongestants are effective and have few adverse
effects. Many health-care providers recommend them for
short-term use for the common cold and sinusitis. A concern
is the significant rebound congestion that occurs if the topical
decongestants are used long term. It can occur in as little as
a week of constant use. Therefore, topical decongestants for
allergic rhinitis, although safe, must be accompanied with
strict patient education to prevent rebound congestion. In
patients who are sensitive to the drying effects of the topical
decongestants, the oral form may be better tolerated. The reverse is also true; in patients sensitive to sympathomimetics,
the topical decongestants are usually tolerated.
Short- Versus Long-Acting
There are short- and long-acting forms of both oral and topical decongestants. In general, the short-acting forms are
better tolerated and have fewer adverse effects. The longeracting forms are useful for patients who require all-day or
all-night relief, if the patients can tolerate them.
Cost
Cost is usually not a major factor in prescribing decongestants, which are available OTC, and generic forms of all the
medications are available.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacotherapeutics: Adverse Drug Reactions:
Adverse effects are minimal at recommended doses, unless
a patient is sensitive to sympathomimetics. CNS effects may
include anxiety, tenseness, restlessness, headache, lightheadedness, dizziness, drowsiness, tremor, insomnia, hallucinations, psychological disturbances, CNS depression, and
weakness. Of these CNS effects, the most common adverse
effects are restlessness and tremors. Cardiovascular adverse
effects include transient hypertension, arrhythmia, and cardiovascular collapse, with hypotension, palpitations, tachycardia, and bradycardia. These adverse reactions are rare at
recommended doses in healthy individuals. Other adverse
effects are nausea, vomiting, pallor, and, rarely, shortness of
breath or respiratory difficulty (at higher doses).
Topical decongestants have adverse reactions related to
the intense vasoconstrictor effect of the nasal spray or sensitivity to additives such as sulfites. Transient stinging is the
most common adverse effect reported. Burning, sneezing,
dryness, and local irritation are all reported with topical
drugs. The most significant adverse reaction with topical decongestants is rebound congestion (rhinitis medicamentosa)
with prolonged or chronic use. This does not occur with
short-term (3 to 5 day) use.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacotherapeutics: Monitoring
There is no specific monitoring required with the decongestants.
Types of Respiratory Drugs:
Bronchodilators: B2RAs:
Pharmacotherapeutics:
Patient Education:
Administration
The first concern that the health-care provider should
address is self-prescribing and dosing of the nonprescription
decongestants. Whether a drug interaction is a concern or a
patient may be taking an inappropriate dose, it is important
for the health-care provider to be aware that the patient may
be taking a decongestant. A thorough history should include
any self-prescribed medications and the amount and timing
of these medications. Patient teaching should include proper
dosing, especially in pediatric patients. Patients with cardiovascular disease, hyperthyroidism, diabetes mellitus, or prostatic hypertrophy should use these products sparingly and
only on the advice of their health-care provider.
When topical decongestants are recommended, it is imperative that the patient be warned about rebound congestion and cautioned to use the medication for only 3 to
5 days or, for chronic allergic rhinitis use, only 2 of every
7 days.
Parents should be cautioned not to use adult-formula
nasal sprays in children. Children’s strength oxymetazoline
(0.025%) and phenylephrine HCl (0.125%) are available.
Adverse Reactions
Patients should notify their health-care provider if insomnia,
dizziness, weakness, tremor, or irregular heartbeat occurs
with topical decongestants. Patients should be cautioned not
to exceed the recommended dosage because higher doses
cause nervousness, dizziness, or sleeplessness.
Lifestyle Management
Patients should maintain adequate hydration while taking decongestants to keep mucus mobile. They should also refrain
from smoking when they are congested. Caffeine-containing
products may cause tachycardia if ingested with decongestants.
Table 17-15 presents available dosage forms.
