McKenna's Pharmacology for Nursing, 2e

482

P A R T 5  Drugs acting on the autonomic nervous system

• Nausea, diarrhoea : These gastrointestinal discomforts often diminish with time. If they become too uncomfortable or do not improve, talk to your healthcare provider. • Dreams, confusion : These are drug effects. If they become too uncomfortable, discuss them with your healthcare provider. • Report any of the following to your healthcare provider: very slow pulse, need to sleep on more pillows at night, difficulty breathing, swelling in the ankles or fingers, sudden weight gain, mental confusion or personality change, fever or rash.

• Avoid over-the-counter medications, including cold and allergy remedies and diet pills. Many of these preparations contain drugs that could interfere with this medication. If you feel that you need one of these, check with your healthcare provider first. • Tell any doctor, nurse, or other healthcare provider that you are taking these drugs, keep all medications out of the reach of children and do not share these drugs with other people.

BETA 1

-SELECTIVE ADRENERGIC BLOCKING

Therapeutic actions and indications The therapeutic effects of these drugs are related to their ability to selectively block beta 1 -receptors in the SNS at therapeutic doses. As a result, these drugs do not block the beta 2 -receptors and therefore do not prevent sympathetic bronchodilation. However, the selectivity is lost with doses higher than the recommended range. The blockade of the beta 1 -receptors in the heart and in the juxtaglomerular apparatus accounts for most of the therapeutic benefits. Decreased heart rate, contrac- tility and excitability, as well as a membrane-stabilising effect, lead to a decrease in arrhythmias, decreased cardiac workload and decreased oxygen consumption. The juxtaglomerular cells are not stimulated to release renin, which further decreases blood pressure. These drugs are useful in treating cardiac arrhythmias, hyper- tension and chronic angina and can help to prevent

AGENTS

Beta 1 -selective adrenergic blocking agents (Table 31.5) have an advantage over the non-selective beta-block- ers in some cases. Because they do not usually block beta 2 -receptor sites, they do not block the sympathetic bronchodilation that is so important for people with lung diseases or allergic rhinitis. Consequently, these drugs are preferred for individuals who smoke or who have asthma, any other obstructive pulmonary disease or seasonal or allergic rhinitis. These selective beta blockers are also used for treating hypertension, angina and some cardiac arrhythmias. Beta 1 -selective adren­ ergic blocking agents include atenolol ( Tenormin ), betaxolol ( Betoptic ), bisoprolol ( Bicor, Bispro ), esmolol ( Brevibloc ) and metoprolol ( Betaloc, Lopresor ) .

TABLE 31.5

DRUGS IN FOCUS Beta 1

-selective adrenergic blocking agents

Drug name

Dosage/route

Usual indications

Initially 50 mg/day PO, may be increased to 100 mg/day

Treatment of MI, chronic angina, hypertension in adults (atenolol is more widely used than the other drugs of this class for hypertension) Available as ophthalmic agent for treatment of ocular hypertension, open-angle glaucoma Treatment of hypertension in adults, alone or as part of combination therapy Treatment of supraventricular tachycardias (e.g. atrial flutter, atrial fibrillation) in adults, and non-compensatory tachycardia when the heart rate must be slowed (IV use only) Treatment of hypertension; prevention of reinfarction after MI; early acute MI treatment; treatment of stable and symptomatic HF (extended-release preparation only)

atenolol (Tenormin)

betaxolol (Betoptic)

1–2 drops (gtts) in affected eye(s) for glaucoma

bisoprolol (Bicor, Bispro)

Initially 1.25 mg/day PO for 1 week, increased weekly to maximum 10 mg/day PO 50–200 mcg/kg per minute IV, with dose based on person’s response

esmolol (Brevibloc)

metoprolol (Betaloc, Lopresor)

50–100 mg PO once daily or b.d. Maximum 400 mg/day