University:
University of North Carolina at Chapel Hill
Course:
NURS 312 | Pharmacology
Academic year:

2020
Views:

80

Pages:

1
Author:

5prinzg1s

1.3 – “Barber Shop”: Barbiturate Barbituratess • Barbiturates are some of the oldest anti-seizure drugs. Nowadays, limited clinical use d/t CV, pulmonary, CNS sedation, & addiction risk. • Uses: critically ill sedation, occasionally antiseizure. • MOA: allosterically bind GABA-A receptor at the different site from benzos (Cab-A cap). Potentiate GABA A transmission throughout the CNS. o Major inhibitory CNS neurotransmitter (along with glycine) (CNS & “take it easy” signs on cab). o Activated GABA-A receptor is a chloride channel (Chlo-rider cab). ↑chloride conductance inhibits synaptic transmission → CNS depression (CNS light on cab). Increased permeability hyperpolarizes & stabilizes membrane potential, making less excitable. o Chloride channel conductance is d/t an increase in duration of opening rather than increased frequency (“Longer hours!”) o Different site altogether from alcohol & barbiturates (drinking man & Ben’s Diner outside) • Generally have longer half-lives than BZD and may have residual hangover effects d/t extended serum half-life (tapered white flag). Exception is thiopental. • Adverse effects: o Clinical utility limited by significant depressive effects. o Half-life is 75 to more than 100 hours, with cumulative effects. Can → profound cardiac & respiratory depression (sweater with brain & heart) & hypotension (fainting) o Can cause severe CNS depression, even progressing to coma. Should always be avoided in the elderly (elderly woman fainting) o Long term use can lead to tolerance (tolerance banner), physical dependence (“addicted to curls” sign) o Potent inducer of CYP450 (kiddie car license plate) • Thiopental (“The Ol’ Quick Shave”). o Used IV for induction of anesthesia, especially in rapid sequence intubation (scrubs with sedated patient with a straw). o Rapid onset (30 seconds) & rapid clearance. Highly lipid soluble → rapid entrance into CNS with equilibration within 1 minute’s loss of consciousness. Duration of action is only 5-10 minutes d/t drug redistribution rather than metabolism (accumulates rapidly in adipose tissue & SKM) (hair “redistributed” onto arms & belly). Outlined at Right: ▪ Decay line (solid black line): rapid decay of plasma thiopental levels d/t redistribution. ▪ Brief peak (dashed line): rapid accumulation of thiopental in brain tissue & rapid redistribution ▪ Growth line (purple line): rapid accumulation of thiopental in muscle & adipose tissue. • Phenobarbital o Used IV for suppression of seizures (unplugging jackhammer; ivy) o One of the oldest antiseizure drugs still in use. For both generalized & focal. Stops any seizure at sufficient doses. ▪ Used as a first line treatment in neonates. ▪ Causes prolonged sedation, so 2nd or 3rd line in adults. • Primidone (perm is done) o Used to treat partial or tonic clonic seizures o Treats essential tremor in low doses; 1st line along with propranolol (stylist with shaking hands).