timolol maleate

timolol maleate

(tye moe' lole)

Apo-Timol (CAN), Betimol, Blocadren, Timoptic, Timoptic-XE

Pregnancy Category C

Drug classes

Beta-adrenergic blocker

Antihypertensive

Antiglaucoma drug

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 decreasing the excitability of the heart, decreasing cardiac output and oxygen consumption, decreasing the release of renin, and lowering BP; reduces IOP by decreasing the production of aqueous humor and possibly by increasing aqueous humor outflow.

Indications

·        Hypertension, used alone or in combination with other antihypertensives, especially thiazide-type diuretics

·        Prevention of reinfarction in MI patients who are hemodynamically stable

·        Prophylaxis of migraine

·        Ophthalmic solution: Reduction of IOP in chronic open-angle glaucoma, some patients with secondary glaucoma, aphakic patients with glaucoma ocular hypertension

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, asthma, COPD, pregnancy, lactation.

·        Use cautiously with diabetes or thyrotoxicosis (timolol can mask the usual cardiac signs of hypoglycemia and thyrotoxicosis).

Available forms

Tablets—5, 10, 20 mg; ophthalmic solution, gel—0.25%, 0.5%

Dosages

ADULTS

Oral

·        Hypertension: Initially, 10 mg bid. Increase dosage at 1-wk intervals to a maximum of 60 mg/day divided into two doses, as needed. Usual maintenance dose is 20–40 mg/day given in two divided doses.

·        Prevention of reinfarction in MI (long-term prophylaxis in patients who survived the acute phase): 10 mg bid PO within 1–4 wk of infarction.

·        Migraine: 10 mg PO bid; during maintenance, the 20 mg/day may be given as a single dose. May be increased to a maximum of 30 mg/day in divided doses or decreased to 10 mg/day. Discontinue if satisfactory response is not obtained after 6–8 wk.

Ophthalmic

Initially, 1 drop of 0.25% solution bid into the affected eye or eyes. Adjust dosage on basis of response to 1 drop of 0.5% solution bid or 1 drop of 0.25% solution daily. When replacing other agents, make change gradually and individualize dosage.

PEDIATRIC PATIENTS

Safety and efficacy not established.

Pharmacokinetics

Route	Onset	Peak
Oral	Varies	1–2 hr
Ophthalmologic	Rapid	1–5 hr

Metabolism: Hepatic; T_1/2: 3–4 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

Adverse effects

Oral

·        Allergic reactions: Pharyngitis, erythematous rash, fever, sore throat, laryngospasm, respiratory distress

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

·        CV: CHF, cardiac arrhythmias, sinoatrial or AV nodal block, 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 (less likely than with propranolol)

·        Other: Decreased exercise tolerance, development of antinuclear antibodies (ANA), hyperglycemia or hypoglycemia, elevated serum transaminase

Ophthalmic

·        Local: Ocular irritation, decreased corneal sensitivity, visual refractive changes, diplopia, ptosis

Interactions

Drug-drug

·        Increased effects with verapamil

·        Increased risk of orthostatic hypotension with prazosin

·        Decreased antihypertensive effects with NSAIDs, clonidine

·        Decreased elimination of theophyllines with resultant decrease in expected actions of both drugs when taken concurrently

·        Peripheral ischemia and possible gangrene with ergotamine, methysergide, dihydroergotamine

·        Increased risk of hypoglycemia and masked signs of hypoglycemia with insulin

·        Hypertension followed by severe bradycardia with epinephrine

·        All of the above may occur with ophthalmic timolol; in addition, additive effects are possible with oral beta-blockers

Drug-lab test

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

Nursing considerations

Assessment

·        History: Sinus bradycardia, second- or third-degree heart block, cardiogenic shock, CHF, asthma, COPD, pregnancy, lactation, diabetes or thyrotoxicosis

·        Physical: Weight, skin condition, neurologic status, P, BP, ECG, respiratory status, renal and thyroid function, 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.

·        Consult with surgeon about withdrawal if patient is to undergo surgery (withdrawal is controversial).

Teaching points

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

·        Avoid driving or dangerous activities if dizziness or shaking occurs.

·        If using ophthalmic form, administer eye drops properly to minimize systemic absorption.

·        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.