Betim
timolol maleate
Pharmacologic class: Beta-adrenergic blocker (nonselective)
Therapeutic class: Antihypertensive, vascular headache suppressant, antiglaucoma agent
Pregnancy risk category C
FDA Box Warning
Exacerbations of angina pectoris and myocardial infarction (MI) may follow abrupt withdrawal of some beta blockers. When discontinuing long-term therapy, particularly in patients with ischemic heart disease, reduce dosage gradually over 1 to 2 weeks and monitor patient carefully. If angina worsens markedly or acute coronary insufficiency develops, reinstate drug promptly (at least temporarily) and take other appropriate measures to manage unstable angina. Caution patient not to interrupt or discontinue therapy without prescriber's advice. Because coronary artery disease is common and may be unrecognized, it may be prudent not to discontinue drug abruptly even in patients treated only for hypertension.
Action
Blocks stimulation of beta1-adrenergic (myocardial) and beta2-adrenergic (pulmonary, vascular, uterine) receptor sites. May reduce aqueous production, which decreases intraocular pressure (IOP).
Availability
Ophthalmic gel: 0.25%, 0.5%
Ophthalmic solution: 0.25%, 0.5%
Tablets: 5 mg, 10 mg, 20 mg
Indications and dosages
➣ Hypertension
Adults: Initially, 10 mg P.O. b.i.d., given alone or with a diuretic; may increase at 7-day intervals as needed. Usual maintenance dosage is 10 to 20 mg daily in two divided doses, up to 60 mg/day.
➣ Acute MI
Adults: 10 mg P.O. b.i.d. starting 1 to 4 weeks after MI
➣ To prevent vascular headaches
Adults: Initially, 10 mg P.O. b.i.d. For maintenance, 20 mg may be given as a single daily dose. Total daily dosage may be increased to a maximum of 30 mg in divided doses or decreased to 10 mg/day, depending on response and tolerance. Withdraw drug if satisfactory response doesn't occur after 6 to 8 weeks at maximum dosage.
➣ Elevated IOP in patients with ocular hypertension or open-angle glaucoma
Adults: One drop of 0.25% to 0.5% ophthalmic solution in affected eye b.i.d., or 0.25% to 0.5% ophthalmic gel in affected eye once daily
Off-label uses
• Angina pectoris
• Supraventricular arrhythmias
Contraindications
• Hypersensitivity to drug or other beta-adrenergic blockers
• Uncompensated heart failure
• Bradycardia or heart block
• Cardiogenic shock
• Bronchial asthma (current or previous), severe chronic obstructive pulmonary disease
Precautions
Use cautiously in:
• renal or hepatic impairment, diabetes mellitus, thyrotoxicosis
• elderly patients
• pregnant or breastfeeding patients
• children (safety not established).
Administration
• Measure apical pulse before giving. If patient has significant bradycardia or tachycardia, withhold dose and consult prescriber.
Adverse reactions
CNS: fatigue, dizziness, asthenia, insomnia, headache, vertigo, nervousness, depression, paresthesia, hallucinations, memory loss, disorientation, emotional lability, clouded sensorium
CV: hypotension, angina pectoris exacerbation, bradycardia, atrioventricular or sinoatrial block, arrhythmias, heart failure
EENT: visual disturbances, dry eyes, tinnitus, nasal congestion
GI: nausea, constipation, diarrhea, abdominal discomfort
GU: erectile dysfunction, decreased libido
Metabolic: hyperuricemia, hypoglycemia, hyperkalemia
Musculoskeletal: joint pain
Respiratory: dyspnea, crackles, bronchospasm, pulmonary edema
Skin: itching, rash
Interactions
Drug-drug. Antihypertensives, nitrates: additive hypotension
Insulin, oral hypoglycemics: altered efficacy of these drugs
Nonsteroidal anti-inflammatory drugs: decreased antihypertensive effect of timolol
Quinidine: inhibited timolol metabolism, leading to increased beta-adrenergic blockade and bradycardia
Reserpine: increased risk of hypotension and bradycardia
Theophylline: reduced effects of both drugs
Drug-diagnostic tests. Antinuclear antibodies: increased titer
Blood urea nitrogen, liver function tests, potassium, uric acid: increased values
Glucose, high-density lipoproteins, hematocrit, hemoglobin: decreased values
Drug-herbs. Ephedra (ma huang), St. John's wort, yohimbine: decreased timolol efficacy
Patient monitoring
• Closely monitor vital signs, blood pressure, cardiovascular status, and ECG.
• Assess respiratory status. Check breath sounds for wheezing and bronchospasm.
• Monitor blood glucose level in patient with diabetes mellitus.
Patient teaching
• Teach patient how to measure pulse before each dose. Instruct him to contact prescriber if pulse is outside established safe range.
Caution patient not to stop taking drug abruptly. Dosage must be tapered.
• Teach patient how to administer eye drops. Instruct him to use drops only as prescribed, because they are absorbed systemically. Caution him not to touch dropper tip to eye or any other surface.
Teach patient to recognize and immediately report significant adverse respiratory, cardiac, and neurologic reactions.
• Inform patient that many over-the-counter drugs and herbs may decrease the efficacy of timolol. Advise him to consult prescriber before using these products.
• Advise diabetic patient that drug may lower blood glucose level. Encourage regular blood glucose monitoring.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.