A sterile sustained release microparticulate composition formulated in an injectable depot form for use in a method of treating at least one cerebral artery in a subarachnoid space at risk of interruption due to a brain injury in a human subject by injection of the composition into a cerebral ventricle, said composition comprising (a) a microparticulate formulation comprising a plurality of microparticles of uniform size distribution of a diameter ranging from 30 μm to 100 μm, wherein each microparticle comprises a matrix formed from a biodegradable polymer selected from the group consisting of polylactide-polyglycolide, poly(orthoester), and poly(anhydride) and a therapeutic amount of at least one therapeutic agent selected from the group consisting of a calcium channel antagonist, an endothelin receptor antagonist, and a transient receptor potential channel antagonist dispersed throughout each microparticle; and (b) a pharmaceutical carrier comprising up to 5% hyaluronic acid, wherein: the therapeutic amount of the at least one therapeutic agent is effective to treat a delayed complication of the interruption of the cerebral artery; the at least one therapeutic agent is gradually released from the composition over an extended period of time, and the composition is flowable around the at least one cerebral artery in the subarachnoid space at risk of interruption due to a brain injury following local delivery; and is effective to release the therapeutic amount of the therapeutic agent in the subarachnoid space without entering systemic circulation in an amount to cause unwanted side effects. (a) a microparticulate formulation comprising a plurality of microparticles of uniform size distribution of a diameter ranging from 30 μm to 100 μm, wherein each microparticle comprises a matrix formed from a biodegradable polymer selected from the group consisting of polylactide-polyglycolide, poly(orthoester), and poly(anhydride) and a therapeutic amount of at least one therapeutic agent selected from the group consisting of a calcium channel antagonist, an endothelin receptor antagonist, and a transient receptor potential channel antagonist dispersed throughout each microparticle; and (b) a pharmaceutical carrier comprising up to 5% hyaluronic acid, wherein: the therapeutic amount of the at least one therapeutic agent is effective to treat a delayed complication of the interruption of the cerebral artery; the at least one therapeutic agent is gradually released from the composition over an extended period of time, and the composition is flowable around the at least one cerebral artery in the subarachnoid space at risk of interruption due to a brain injury following local delivery; and is effective to release the therapeutic amount of the therapeutic agent in the subarachnoid space without entering systemic circulation in an amount to cause unwanted side effects. the therapeutic amount of the at least one therapeutic agent is effective to treat a delayed complication of the interruption of the cerebral artery; the at least one therapeutic agent is gradually released from the composition over an extended period of time, and the composition is flowable around the at least one cerebral artery in the subarachnoid space at risk of interruption due to a brain injury following local delivery; and is effective to release the therapeutic amount of the therapeutic agent in the subarachnoid space without entering systemic circulation in an amount to cause unwanted side effects.