Article: Timolol

Timolol
Systematic (IUPAC) name
(S)-1-(tert-butylamino)- 3-(4-morpholino-1,2,5-thiadiazol-3-yloxy)propan-2-ol
Identifiers
CAS number	26839-75-8
ATC code	C07AA06
PubChem	5478
DrugBank	APRD00229
Chemical data
Formula	C13H24N4O3S
Mol. weight	316.421 g/mol
Pharmacokinetic data
Bioavailability	60%
Metabolism	Hepatic: 80%
Half life	2.5-5 hours
Excretion	Renal
Therapeutic considerations
Pregnancy cat.	C(AU) C(US)
Legal status	℞ Prescription only
Routes	oral, Ophthalmic

Timolol maleate is a non-selective beta-adrenergic receptor blocker. In its oral form (Blocadren®), it is used to treat high blood pressure and prevent heart attacks, and occasionally to prevent migraine headaches. In its ophthalmic form (Timoptic®), it is used to treat open-angle and occasionally secondary glaucoma.

Side effects

The most serious possible side effects include cardiac arrhythmias and severe bronchospasms. Timolol can also lead to fainting, stroke, congestive heart failure, depression, confusion, and impotence.

Usual Dosage

• Children and Adults: Ophthalmic: Initial: 0.25% solution, instill 1 drop twice daily; increase to 0.5% solution if response not adequate; decrease to 1 drop/day if *controlled; do not exceed 1 drop twice daily of 0.5% solution Adults: Oral:
• Hypertension: Initial: 10 mg twice daily, increase gradually every 7 days, usual dosage: 20-40 mg/day in 2 divided doses; maximum: 60 mg/day
• Prevention of myocardial infarction: 10 mg twice daily initiated within 1-4 weeks after infarction
• Migraine headache: Initial: 10 mg twice daily, increase to maximum of 30 mg/day

Formulations

• Gel-forming solution, ophthalmic, as maleate (Timoptic-XE®): 0.25% (2.5 mL, 5 mL); 0.5% (2.5 mL, 5 mL)
• Solution, ophthalmic, as hemihydrate (Betimol®): 0.25% (5 mL, 10 mL, 15 mL); 0.5% (5 mL, 10 mL, 15 mL) [contains benzalkonium chloride]
• Solution, ophthalmic, as maleate: 0.25% (5 mL, 10 mL, 15 mL); 0.5% (5 mL, 10 mL, 15 mL) [contains benzalkonium chloride]
• Timoptic®: 0.25% (5 mL, 10 mL); 0.5% (5 mL, 10 mL) [contains benzalkonium chloride]
• Solution, ophthalmic, as maleate [preservative free] (Timoptic® OcuDose®): 0.25% (0.2 mL);0.5% (0.2 mL) [single use]
• Tablet, as maleate (Blocadren®): 5 mg, 10 mg, 20 mg

Brand Names

In Canada Apo®-Timol, Apo®-Timop, Gen-Timolol®, Nu-Timolol®, Phoxal-timolol®, PMS-Timolol®, Tim-AK®. In United States Betimol®, Blocadren®, Istalol®, Timoptic® OcuDose®. In both Canada and US: Timoptic® and Timoptic-XE®.

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