TIMOLOL MALEATE

TIMOLOL MALEATE
(tye'moe-lole)
Betimol, Blocadren, Istalol, Timoptic, Timoptic XE
Classifications: beta-adrenergic antagonist; eye preparation; miotic;
Therapeutic: miotic

Prototype: Propranolol
Pregnancy Category: C

Availability

5 mg, 10 mg, 20 mg tablets; 0.25%, 0.5% ophthalmic solution or gel

Action

Nonselective beta-adrenergic antagonist. Demonstrates antihypertensive, antiarrhythmic, and antianginal properties, and suppresses plasma renin activity. When applied topically, lowers elevated and normal intraocular pressure (IOP) by reducing formation of aqueous humor and possibly by increasing outflow.

Therapeutic Effect

Topically, lowers elevated and normal intraocular pressure (IOP). Orally, therapeutically useful for mild hypertension and migraine headaches.

Uses

Topically (ophthalmic solution) to reduce elevated IOP in chronic, open-angle glaucoma, aphakic glaucoma, secondary glaucoma, and ocular hypertension. May be used alone or in conjunction with epinephrine, pilocarpine, or a carbonic anhydrase inhibitor such as acetazolamide. Oral preparation is used as monotherapy or in combination with a thiazide diuretic to prevent reinfarction after MI and to treat mild hypertension.

Unlabeled Uses

Prophylactic management of stable, uncomplicated angina pectoris and migraine headaches.

Contraindications

Bronchospasm; severe COPD; bronchial asthma; heart failure; pregnancy (category C), abrupt discontinuation, acute bronchospasm, AV block, bradycardia, cardiogenic shock, acute pulmonary edema, compromised left ventricular dysfunction, Raynaud's disease. Safety in children is not established.

Cautious Use

Bronchitis, patients subject to bronchospasm, asthma; sinus bradycardia, greater than first-degree heart block, heart failure; renal impairment; hepatic disease; vasospastic angina, peripheral vascular disease; pheochromocytoma; thyrotoxicosis, hyperthyroidism; right ventricular failure secondary to pulmonary hypertension, COPD; stroke, cerebrovascular disease; depression; older adults; psoriasis; myasthenia gravis; concomitant use with adrenergic augmenting drugs (e.g., MAO inhibitors).

Route & Dosage

Glaucoma

See Appendix A-1.


Hypertension
Adult: PO 10 mg b.i.d., may increase to 60 mg/d in 2 divided doses

Angina
Adult: PO 15–45 mg in 3 divided doses

Administration

Oral
  • Give with fluid of patient's choice; tablet may be crushed.
  • Make dosage increases for hypertension at weekly intervals.

Adverse Effects (≥1%)

CNS: Fatigue, lethargy, weakness, somnolence, anxiety, headache, dizziness, confusion, psychic dissociation, depression. CV: Palpitation, bradycardia, hypotension, syncope, AV conduction disturbances, CHF, aggravation of peripheral vascular insufficiency. Special Senses: Eye irritation including conjunctivitis, blepharitis, keratitis, superficial punctate keratopathy. GI: Anorexia, dyspepsia, nausea. Skin: Rash, urticaria. Respiratory: Difficulty in breathing, bronchospasm. Body as a Whole: Fever. Metabolic: Hypoglycemia, hypokalemia.

Interactions

Drug: antihypertensive agents, diuretics, selective serotonin reuptake inhibitors potentiate hypotensive effects; nsaids may antagonize hypotensive effects.

Pharmacokinetics

Absorption: 90% absorbed from GI tract; 50% reaches systemic circulation; some systemic absorption from topical application. Peak: 1–2 h PO; 1–5 h topical. Distribution: Distributed into breast milk. Metabolism: 80% metabolized in liver to inactive metabolites. Elimination: In urine.

Nursing Implications

Assessment & Drug Effects

  • Check pulse before administering timolol, topical or oral. If there are extremes (rate or rhythm), withhold medication and call the physician.
  • Assess pulse rate and BP at regular intervals and more aften in patients with severe heart disease.
  • Note: Some patients develop tolerance during long-term therapy.

Patient & Family Education

  • Be aware that drug may cause slight reduction in resting heart rate. Learn how to assess pulse rate and report significant changes. Consult physician for parameters.
  • Do not stop drug abruptly; angina may be exacerbated. Dosage is reduced over a period of 1–2 wk.
  • Report difficulty in breathing promptly to physician. Drug withdrawal may be indicated.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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