Betimol® (timolol ophthalmic solution), 0.25% and 0.5%, is a non-selective beta-adrenergic antagonist for ophthalmic use. The chemical name of the active ingredient is (S)-1-[(1,1-dimethylethyl)amino]-3-[[4-(4-morpholinyl)-1,2,5-thiadiazol-3-yl]oxy]-2-propanol. Timolol hemihydrate is the levo isomer. Specific rotation is [α]²⁵ 405nm=-16° (C=10% as the hemihydrate form in 1N HCI).

The molecular formula of timolol is Formula C₁₃H₂₄N₄O₃S and its structural formula is:

Timolol (as the hemihydrate) is a white, odorless, crystalline powder which is slightly soluble in water and freely soluble in ethanol. Timolol hemihy-drate is stable at room temperature.

Betimol® (timolol ophthalmic solution) is a clear, colorless, isotonic, sterile, microbiologically preserved phosphate buffered aqueous solution. It is supplied in two dosage strengths, 0.25% and 0.5%.

Each mL of Betimol® 0.25% contains 2.56 mg of timolol hemihydrate equivalent to 2.5 mg timolol.

Each mL of Betimol® 0.5% contains 5.12 mg of timolol hemihydrate equivalent to 5.0 mg timolol.

Inactive ingredients: monosodium and disodium phosphate dihydrate to adjust pH (6.5 - 7.5) and water for injection, benzalkonium chloride 0.01% added as preservative.

The osmolality of Betimol® (timolol ophthalmic solution) is 260 to 320 mOsmol/kg.

Last reviewed on RxList: 3/26/2009
This monograph has been modified to include the generic and brand name in many instances.