McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 3 1 Adrenergic blocking antagonists

hypersensitivity reactions ; presence of any cardiovascular diseases, which may be exacerbated by the use of this drug ; and current status of pregnancy or breastfeeding because of the potential for adverse effects to the fetus or neonate. ■ ■ Perform a physical assessment to establish baseline data for determining the effectiveness of the drug and occurrence of any adverse effects. ■ ■ Assess orientation, affect and reflexes to monitor for CNS changes related to drug therapy ; monitor cardiovascular status, including pulse, blood pressure, peripheral perfusion and cardiac output, to determine changes in function , and urine output, which will reflect perfusion of the kidney as another assessment of cardiac function. Implementation with rationale ■ ■ Monitor heart rate and blood pressure closely and frequently for changes to anticipate the need to discontinue the drug if adverse reactions are severe ; provide supportive management if needed. ■ ■ Inject phentolamine directly into the area of extravasation of adrenaline or dopamine to prevent local cell death. ■ ■ Arrange for supportive care and comfort measures, such as rest, environmental control and other measures, to decrease CNS irritation ; provide headache medication to alleviate discomfort . ■ ■ Institute safety measures to prevent injury if the person experiences weakness, dizziness or orthostatic hypotension. ■ ■ Provide thorough teaching, including drug name, dosage and schedule for administration; potential adverse effects and measures to prevent them; and warning signs of problems, to enhance knowledge about drug therapy and to promote compliance.

■■ Non-selective alpha-adrenergic blocking agents are used to treat phaeochromocytoma, a tumour of the adrenal medulla. A reflex tachycardia commonly occurs when the blood pressure falls. ■■ Phentolamine is a non-selective alpha-adrenergic blocker used most commonly for the prevention and treatment of dermal necrosis and sloughing associated with IV extravasation of noradrenaline or dopamine. ■ ■ Offer support and encouragement to help the person deal with the need for the drug. Evaluation ■ ■ Monitor response to the drug (improvement in signs and symptoms of phaeochromocytoma, improvement in tissue condition after extravasation). ■ ■ Monitor for adverse effects (orthostatic hypotension, arrhythmias, CNS effects such as headache or dizziness). ■ ■ Evaluate the effectiveness of the teaching plan (person can name drug, dosage, adverse effects to watch for and specific measures to avoid them). ■ ■ Monitor the effectiveness of support measures.

KEY POINTS

ALPHA 1

-SELECTIVE ADRENERGIC

BLOCKING AGENTS

Alpha 1 -selective adrenergic blocking agents are drugs -receptors. These drugs include alfuzosin ( Xatral SR ) (not available in New Zealand) , doxazosin (generic; not available in Aus- tralia), prazosin ( Minipress ), tamsulosin ( Flomaxtra ) and terazosin ( Hytrin ) (see Table 31.3). that have a specific affinity for alpha 1

TABLE 31.3

DRUGS IN FOCUS Alpha 1

-selective adrenergic blocking agents

Drug name

Dosage/route

Usual indications

alfuzosin (Xatral SR)

10 mg/day PO

Treatment of benign prostatic hyperplasia (BPH)

1 mg/day PO up to 16 mg/day PO for hypertension; 1–8 mg/day PO for BPH Adult: 1 mg PO b.d. to t.d.s. with maintenance at 6–15 mg/day PO in divided doses 0.4–0.8 mg/day PO 30 minutes after the same meal each day 1–5 mg/day PO, preferably at bedtime for hypertension; 10 mg/day PO for BPH

Treatment of hypertension and BPH

doxazosin (generic)

prazosin (Minipress)

Treatment of hypertension alone or in combination with other drugs

tamsulosin (Flomaxtra)

Treatment of BPH

terazosin (Hytrin)

Treatment of hypertension and BPH