metoprolol

metoprolol

(me toe' proe lole)

Apo-Metoprolol (CAN), Betaloc (CAN), Lopressor, Novometoprol (CAN), Nu-Metop (CAN)

metoprolol succinate

Toprol-XL

metoprolol tartrate

Lopressor Injection

Pregnancy Category C

Drug classes

Beta₁-selective adrenergic blocker

Antihypertensive

Therapeutic actions

Competitively blocks beta-adrenergic receptors in the heart and juxtaglomerular apparatus, decreasing the influence of the sympathetic nervous system on these tissues and the excitability of the heart, decreasing cardiac output and the release of renin, and lowering BP; acts in the CNS to reduce sympathetic outflow and vasoconstrictor tone.

Indications

·        Hypertension, alone or with other drugs, especially diuretics

·        Immediate-release tablets and injection: Prevention of reinfarction in MI patients who are hemodynamically stable or within 3–10 days of the acute MI

·        Treatment of angina pectoris

·        Toprol-XL only: Treatment of stable, symptomatic CHF of ischemic, hypertensive, or cardiomyopathic origin

Contraindications and cautions

·        Contraindicated with sinus bradycardia (HR < 45 beats/min), second- or third-degree heart block (PR interval > 0.24 sec), cardiogenic shock, CHF, systolic BP < 100 mm Hg; lactation.

·        Use cautiously with diabetes or thyrotoxicosis; asthma or COPD; pregnancy.

Available forms

Tablets—50, 100 mg; ER tablets—25, 50, 100, 200 mg; injection—1 mg/mL

Dosages

ADULTS

·        Hypertension: Initially, 100 mg/day PO in single or divided doses; gradually increase dosage at weekly intervals. Usual maintenance dose is 100–450 mg/day.

·        Angina pectoris: Initially, 100 mg/day PO in two divided doses; may be increased gradually, effective range 100–400 mg/day.

·        MI, early treatment: Three IV bolus doses of 5 mg each at 2-min intervals with careful monitoring. If these are tolerated, give 50 mg PO 15 min after the last IV dose and q 6 hr for 48 hr. Thereafter, give a maintenance dosage of 100 mg PO bid. Reduce initial PO doses to 25 mg, or discontinue in patients who do not tolerate the IV doses.

·        MI, late treatment: 100 mg PO bid as soon as possible after infarct, continuing for at least 3 mo and possibly for 1–3 yr.

ER tablets

·        Hypertension: 50–100 mg/day PO as one dose.

·        Angina: 100 mg/day PO as one dose.

·        CHF: 12.5–25 mg/day Toprol-XL for 2 wk; may then be increased by 25 mg every 2 wk to a maximum of 200 mg.

PEDIATRIC PATIENTS

Safety and efficacy not established.

Pharmacokinetics

Route	Onset	Peak	Duration
Oral	15 min	90 min	15–19 hr
IV	Immediate	60–90 min	15–19 hr

Metabolism: Hepatic; T_1/2: 3–4 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

IV facts

Preparation: No additional preparation is required.

Infusion: Inject directly into vein or into tubing of running IV over 1 min. Inject as a bolus; monitor carefully; wait 2 min between doses; do not give if bradycardia of < 45 beats/min, heart block, systolic pressure < 100 mm Hg.

Incompatibilities: Do not mix with amino acids, aztreonam, dopamine.

Adverse effects

·        Allergic: Pharyngitis, erythematous rash, fever, sore throat, laryngospasm

·        CNS: Dizziness, vertigo, tinnitus, fatigue, emotional depression, paresthesias, sleep disturbances, hallucinations, disorientation, memory loss, slurred speech

·        CV: CHF, cardiac arrhythmias, peripheral vascular insufficiency, claudication, CVA, pulmonary edema, hypotension

·        Dermatologic: Rash, pruritus, sweating, dry skin

·        EENT: Eye irritation, dry eyes, conjunctivitis, blurred vision

·        GI: Gastric pain, flatulence, constipation, diarrhea, nausea, vomiting, anorexia, ischemic colitis, renal and mesenteric arterial thrombosis, retroperitoneal fibrosis, hepatomegaly, acute pancreatitis

·        GU: Impotence, decreased libido, Peyronie's disease, dysuria, nocturia, frequent urination

·        Musculoskeletal: Joint pain, arthralgia, muscle cramp

·        Respiratory: Bronchospasm, dyspnea, cough, bronchial obstruction, nasal stuffiness, rhinitis, pharyngitis

·        Other: Decreased exercise tolerance, development of ANA, hyperglycemia or hypoglycemia, elevated serum transaminase, alkaline phosphatase

Interactions

Drug-drug

·        Increased effects of metoprolol with verapamil, cimetidine, methimazole, propylthiouracil

·        Increased effects of both drugs if metoprolol is taken with hydralazine

·        Increased serum levels and toxicity of IV lidocaine, if given concurrently

·        Increased risk of orthostatic hypotension with prazosin

·        Decreased antihypertensive effects if taken with NSAIDs, clonidine, rifampin

·        Decreased therapeutic effects with barbiturates

·        Hypertension followed by severe bradycardia if given concurrently with epinephrine

Drug-lab test

·        Possible false results with glucose or insulin tolerance tests (oral)

Nursing considerations

Assessment

·        History: Sinus bradycardia (HR < 45 beats/min), second- or third-degree heart block (PR interval > 0.24 sec), cardiogenic shock, CHF, systolic BP < 100 mm Hg; diabetes or thyrotoxicosis; asthma or COPD; lactation, pregnancy

·        Physical: Weight, skin condition, neurologic status, P, BP, ECG, respiratory status, renal and thyroid function tests, blood and urine glucose

Interventions

·        WARNING: Do not discontinue drug abruptly after long-term therapy (hypersensitivity to catecholamines may have developed, causing exacerbation of angina, MI, and ventricular arrhythmias). Taper drug gradually over 2 wk with monitoring.

·        Ensure that patient swallows the ER tablets whole; do not cut, crush, or chew them. XL tablets may be divided at the score; divided tablets should be swallowed whole, not crushed or chewed.

·        Consult physician about withdrawing drug if patient is to undergo surgery (controversial).

·        Give oral drug with food to facilitate absorption.

·        Provide continual cardiac monitoring for patients receiving IV metoprolol.

Teaching points

·        Do not stop taking this drug unless instructed to do so by a health care provider.

·        Swallow the extended-release tablets whole; do not cut, crush, or chew them. If using Toprol XL, you can divide the tablets at the score; divided tablets must be swallowed whole, not crushed or chewed.

·        You may experience these side effects: Dizziness, drowsiness, light-headedness, blurred vision (avoid driving or dangerous activities); nausea, loss of appetite (eat frequent small meals); nightmares, depression (discuss change of medication); sexual impotence.

·        Report difficulty breathing, night cough, swelling of extremities, slow pulse, confusion, depression, rash, fever, sore throat.

Adverse effects in Italic are most common; those in Bold are life-threatening.