Benadryl – Pharmacology for Nurses: Practical Applications

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Chapter 36: Antihistamines, Decongestants, Antitussives, and Expectorant Test, Benadryl

The key terms in this Pharmacology course include Antihistamines, Decongestants, Antitussives, Expectorant, Benadryl, Pharmacology for Nurses: Practical Applications

A patient will be receiving diphenhydramine (Benadryl) via a PEG tube, 25 mg, every 8 hours for an allergic rash. The medication is available as a 12.5 mg/5 mL syrup. Identify how many milliliters will the nurse administer with each dose. __

Correct Answer

10 mL

12.5 mg:5 mL :: 25 mg:x mL.
(12.5 × x) = (5 × 25); 15.5x = 125; x = 10 mL.

A patient has been advised to add a nasal spray (an adrenergic decongestant) to treat a cold. The nurse will include which instruction?

“Avoid use of this spray if a fever develops.”

“Limit use of this spray to 3 to 5 days.”

“You won’t see effects for at least 1 week.”

“Continue the spray until nasal stuffiness has resolved.”

Frequent, long-term, or excessive use of adrenergic nasal decongestants may lead to rebound congestion if used beyond the recommended time. The other instructions are incorrect.

When teaching a patient who will be receiving antihistamines, the nurse will include which instructions? (Select all that apply.)

“Avoid activities that require alertness until you know how adverse effects are tolerated.”

“Antihistamines may cause restlessness and disturbed sleep.”

“Take the medication with food to minimize gastrointestinal distress.”

“Drink extra fluids if possible.”

“Take the medication on an empty stomach to maximize absorption of the drug.”

“Antihistamines are generally safe to take with over-the-counter medications.”

Antihistamines should be taken with food, even though this slightly reduces the absorption of the drug, so as to minimize the gastrointestinal upset that can occur. Over-the-counter medications must not be taken with an antihistamine unless approved by the physician because of the serious drug interactions that may occur. Drinking extra fluids will help to ease the removal of secretions, and activities that require alertness, such as driving, must not be engaged in until the patient knows how he or she responds to the sedating effects of antihistamines.

A child will be receiving diphenhydramine (Benadryl), 5 mg/kg/day, in divided doses, every 6 hours. The child weighs 80 pounds. Identify how many milligrams of medication will the child receive with each dose. (record answer using one decimal place) __

Correct Answers

45.5 mg

80 pounds ÷ 2.2 = 36.36, which rounds to 36.4 kg.
5 mg/kg/day × 36.4 kg = 182 mg/day.
With doses given every 6 hours, there will be 4 total doses in a 24-hour period (24 ÷ 6 = 4).
To calculate milligrams per dose: 182 mg/day ÷ 4 doses/day = 45.5 mg/dose.

The nurse will instruct patients about a possible systemic effect that may occur if excessive amounts of topically applied adrenergic nasal decongestants are used. Which systemic effect may occur?





Although a topically applied adrenergic nasal decongestant can be absorbed into the bloodstream, the amount absorbed is usually too small to cause systemic effects at normal dosages. Excessive dosages of these medications, however, are more likely to cause systemic effects elsewhere in the body. These may include cardiovascular effects, such as hypertension and palpitations, and central nervous system effects, such as headache, nervousness, and dizziness. The other options are incorrect.

When giving dextromethorphan, the nurse understands that this drug suppresses the cough reflex by which mechanism of action?

Anesthetizing the stretch receptors

Decreasing the viscosity of the bronchial secretions

Causing depression of the central nervous system

Having direct action on the cough center

Dextromethorphan suppresses the cough reflex through a direct action on the cough center. The other options are incorrect.