Drugs that inhibit the actions of the sympathetic nervous system by any mechanism. The most common of these are the adrenergic antagonists and drugs that deplete norepinephrine or reduce the release of transmitters from adrenergic postganglionic terminals (see adrenergic agents). Drugs that act in the central nervous system to reduce sympathetic activity (e.g., centrally acting alpha-2 adrenergic agonists, see adrenergic alpha-agonists) are included here.