Timolol maleate is a non-selective beta-adrenergic receptor blocking agent. Its chemical name is (-)-l-(tert-butylamino)-3-[(4-morpholino-l,2,5-thiadiazol-3-yl)oxy]-2-propanolmaleate (1:1) (salt). Timolol maleate possesses an asymmetric carbon atom in its structure and is provided as the levo-isomer. The optical rotation of timolol maleate is: