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timolol (Blocadren, Timoptic, Betimol, Istalol)

Tradename: Blocadren. Indications: 1) ophthalmic agent: a) ocular hypertension b) open-angle glaucoma c) closed-angle glaucoma d) secondary glaucoma [7] 2) systemic agent ? Contraindications: Caution: 1) uncompensated congestive heart failure 2) bradycardia 3) severe COPD Dosage: - 1 drop OU BID Timoptic (timolol maleate): 0.25% & 0.5% 5,10 & 15 mL Istolol (timolol maleate): 0.5% Betimol (timolol hemihydrate:) 0.25% & 0.5% 5,10 & 15 mL Timoptic XE - 1 drop OU QD - 0.25%, 0.5% Pharmacokinetics: 1) intraocular pressure reduction within 15-30 minutes 2) maximal reduction in 1-5 hours 3) duration of action: 24 hours 4) metabolized in the liver by cyt P450 2D6 Adverse effects: 1) ophthalmic agent: - not common (1-10%) - alopecia, burning & stinging of eyes - orthostatic hypotension [11] - uncommon (< 1%) - rash, blepharitis, conjunctivitis, keratitis, visual disturbances - hallucinations [9,10] - significant blood levels with ophthalmic agent [6] - see oral (systemic) administration 2) oral (systemic) administration) - common (> 10%) - sexual dysfunction - less common (1-10%) - bradycardia, arrhythmia, reduced peripheral circulation, dizziness, fatigue, itching, weakness, burning eyes, stinging eyes, dyspnea - uncommon (< 1%) - chest pain, congestive heart failure, hallucinations, mental depression, anxiety, nightmares, rash, diarrhea, nausea/vomiting, epeigastric discomfort, numbness in toes & fingers, dry sore eyes * according to ref [11] timolol causes more orthostatic hypotension than brimonidine Drug interactions: 1) phenothiazine & cimetidine may decrease plasma levels 2) any drug that inhibits cyt P450 2D6 may increase levels of timolol Laboratory: 1) specimen: serum, plasma (EDTA, heparin) 2) methods: TLC, GC, HPLC 3) no good correlation of plasma levels with therapeutic effect Mechanism of action: - reduction aqueous humor formation in the ciliary body in the eye - depresses intraocular pressure 18-34% within first few treatments - owever, there are short-term escape & long-term drift effects in some patients, i.e., tolerance develops - efficacy of timolol in lowering intraocular pressure during sleep may be limited [8]

Interactions

drug interactions drug adverse effects (more general classes)

Related

cytochrome P450 2D6 (cytochrome P450 2D, cytochrome P450 DB1, debrisoquine-4-hydroxylase, CYP2D6)

General

non-specific beta-adrenergic receptor antagonist (non-specific beta-blocker) propanolamine

Properties

MISC-INFO: elimination route LIVER KIDNEY 1/2life 3.0-5.2 HOURS therapeutic-range 3-56 NG/ML protein-binding 60% elimination by hemodialysis - pregnancy-category C safety in lactation ? -

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  3. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  4. Clinical Guide to Laboratory Tests, NW Tietz (ed) 3rd ed, WB Saunders, Philadelpha 1995
  5. Prescriber's Letter 13(3): 2006 Cytochrome P450 drug interactions Detail-Document#: 220233 (subscription needed) http://www.prescribersletter.com
  6. Prescriber's Letter 17(3): 2010 PATIENT HANDOUT: How to Use Eyedrops COMMENTARY: Systemic Effects of Ophthalmic Beta-Blockers PATIENT HANDOUT SPANISH VERSION: Como usar las gotas para los ojos Detail-Document#: 260309 (subscription needed) http://www.prescribersletter.com
  7. bacterial infections due to susceptible organisms
  8. Wikipedia: Timolol https://en.wikipedia.org/wiki/Timolol
  9. Cimolai N. Neuropsychiatric adverse events from topical ophthalmic timolol. Clin Med Res. 2019;17(3-4):90-96 PMID: 31462538 PMCID: PMC6886891 Free PMC article http://www.clinmedres.org/content/17/3-4/90
  10. Negri L, Ferreras A, Iester M. Timolol 0.1% in glaucomatous patients: efficacy, tolerance, and quality of life. J Ophthalmol. 2019 May 2;2019:4146124 PMID: 31191995 PMCID: PMC6525866 Free PMC article https://www.hindawi.com/journals/joph/2019/4146124/
  11. NEJM Knowledge+ Ophthalmology

Component-of

brimonidine/timolol dorzolamide/timolol (Cosopt) hydrochlorothiazide/timolol; HCTZ/timolol (Timolide)