Described herein are compounds and compositions for treating glaucoma and/or reducing intraocular pressure. Compositions may comprise an isoquinoline compound and a prostaglandin or a prostaglandin analog. Compounds described herein include those in which an isoquinoline compound is covalently linked to a prostaglandin or a prostaglandin analog, and those in which an isoquinoline compound and a prostaglandin free acid together form a salt.