B-adrenergic (beta) blockers reduce blood pressure by blocking the effects of epinephrine. This blocker helps the heart relax. The beats slower, the left ventricle fills more completely, vessels become more open, and the heart uses less force to work (Woo & Wynne, 2011). Cardiac output is reduced, causing a decrease in peripheral vascular resistance and a decrease in renin activity (Zisaki et al., 2015).
Common agents include:
- Acebutolol (Sectral)
- Atenolol (Tenormin)
- Metoprolol (Lopressor)
- Labetalol (Trandate)
- Propranolol (Inderal)
- Bisoprolol (Zebeta)
- Nadolol (Corgard)
Beta-blockers are, for the most part, absorbed in the GI tract, metabolized by the liver and excreted through the renal system. Some beta-blockers, such as propranolol and metoprolol, are more highly bound to protein than the others in this class (Zisaki et al., 2015).
It is important to note that several medications interact with beta-blockers:
- Antacids can delay absorption
- NSAIDs can decrease the hypotensive effects
- Lidocaine toxicity can occur
- Diabetic medications may need to be altered
Also, adverse reactions include bradycardia, angina, heart failure, arrhythmias, fainting, fluid retention, peripheral edema, nausea and vomiting, diarrhea, and difficulty breathing due to bronchiole constriction (Nursing, 2016).
Atenolol (Tenormin) initial IV dosage is 1.25 to 5 mg every 6-12 hours, have been used in the short-term management of patients unable to take oral tabs. MI early treatment: 5 mg slow IV over 5 minutes; may repeat in 10 minutes. If both doses are tolerated, may start oral atenolol 50 mg every 12 hours or 100 mg/day for 6-9 days post-myocardial infarction. Oral: Follow IV dose with 100 mg/day or 50 mg twice daily for 6 to 9 days post-myocardial infarction (Global, 2018).
Esmolol (Brevibloc) used for supraventricular tachycardia or gradual control of postoperative tachycardia/hypertension IV loading dose: 500 mcg/kg over 1 minute; follow with a 50 mcg/kg/minute infusion for 4 minutes; response to this initial infusion rate may be a rough indication of the responsiveness of the ventricular rate. The infusion may be continued at 50 mcg/kg/minute or, if the response is inadequate, titrated upward in 50 mcg/kg/minute increments (increased no more frequently than every 4 minutes) to a maximum of 200 mcg/kg/minute (Global, 2018).
To achieve a more rapid response, following the initial loading dose and 50 mcg/kg/minute infusion, re-bolus with a second 500 mcg/kg loading dose over 1 minute, and increase the maintenance infusion to 100 mcg/kg/minute for 4 minutes. If necessary, a third (and final) 500 mcg/kg loading dose may be administered before increasing to an infusion rate of 150 mcg/minute. After 4 minutes of the 150 mcg/kg/minute infusion, the infusion rate may be increased to a maximum rate of 200 mcg/kg/minute (without a bolus dose) (Global, 2018).
Supraventricular tachycardias (SVT) IV dose range: Usual dosage range is 50-200 mcg/kg/minute with average dose of 100 mcg/kg/minute (Global, 2018).
Labetalol (Normodyne) use in hypertensive emergency dose is 20mg IV slow injection, then 40-80 mg IV every 10 minutes as needed. (up to 300 mg total dose) until desired BP is reached or start continuous infusion: 2 mg/min (range: 1 to 3 mg/min)–titrate to BP.
Metoprolol (Lopressor) use in Hypertension/ventricular rate control IV dose (in patients having nonfunctioning GI tract): Initial: 1.25-5 mg every 6-12 hours; titrate initial dose to the response. Initially, low doses may be appropriate to establish response; however, up to 15 mg every 3-6 hours has been employed. Use in MI, initial IV dose 5 mg every 2 minutes for 3 doses in the early treatment of myocardial infarction; after that, give 50 mg orally every 6 hours 15 minutes after last IV dose and continue for 48 hours; then administer a maintenance dose of 100 mg twice daily. When administered acutely for cardiac treatment, monitor ECG and blood pressure (Global, 2018).
Propranolol (Inderal) use in life-threatening arrhythmia dose is usually 1- 3 mg (maximum rate: 1 mg/min)-may dilute in 50 mL D5W. May repeat 1 mg dose every 5 minutes to a maximum of 5 mg total. Use subsequent doses no sooner than 4 hours. May start IV infusion: usual rate: 2 to 3 mg/hr. Titrate to HR/BP (Global, 2018).
- Check apical pulse. Some medications, such as metoprolol, should be held if the apical pulse is less than 60 beats/minute.
- Educate the patient not to stop this medication suddenly. Stopping this medication can cause angina, arrhythmia, and MI.
- Monitor renal and liver laboratory results.
- Assess for adverse reactions.
- Educate the patient on medication interactions.