Belladonna/Phenobarbital

**Semantic type:** Pharmacologic Substance

**Definition:** A combination preparation containing the belladonna alkaloids atropine sulfate, hyoscyamine sulfate, and scopolamine hydrobromide, and the barbiturate phenobarbital with antispasmodic, anxiolytic and sedative activities. The belladonna alkaloids bind to and block muscarinic receptors in the gastrointestinal (GI) tract. This leads to a decrease in stomach secretions, GI motility and GI spasms. Phenobarbital binds to a distinct site on the gamma-aminobutyric acid (GABA)-A subtype receptor in the central nervous system (CNS), thereby increasing the influx of chloride ions into the neuron and potentiating GABA-induced increases in chloride conductance. This enhances postsynaptic responses to the inhibitory actions of GABA and causes CNS depression.

**Synonyms:** - Belladonna Alkaloids/Phenobarbital