Barbituates Flashcards
Mechanism of Action of Methohexitol-Brevitol?
“Decreases the rate of dissociation from GABA receptor. Increases duration of Cl- channel remaining open and allowing Cl- to flow into the cell. This hyperpolarizes the cell and makes it more difficult to create a neuronal transmission.
Suppresses RAS and enhances Sleep
↓transmission in sympathetic ganglion
↓post synaptic membrane sensitivity to ACh”
Indications, onset of action, E 1/2t, protein bound, and Metabolism of Methohexitol-Brevitol?
1) Induction
2) Onset: rapid
3) E1/2 t: 4 hrs
4) 70%pB
5) “Dealkylation/oxidation to hydromethohexitol
Renal/fecal elimination”
Adverse Effects of Methohexitol-Brevitol?
"Induces seizures Excitatory Skeletal muscle effects Hiccups/cough/laryngospasm Vasodilation = reflex tachy Decreased CBF, ICP and CMRO2, isoelectric EEG Release Histamine = ↑HR and ↓BP Dose dependent Resp depression Pain on injection Decreased threshold for pain Cype450 inducer"
Contraindications of Methohexitol-Brevitol?
"Seizure history Pregnancy LR = precipitation Porphyria Asthma"
Dosage of Methohexitol-Brevitol?
“1-2mg/kg IV
20-30mg PR peds”
What is the class of Thiopental-TPL?
“Alkaline – barbituric acid
Sulfur at carbon #2”
What is the MOA of Thiopental-TPL?
“Decreases the rate of dissociation from GABA receptor. Increases duration of CL- channel remaining open and allowing Cl- to flow into the cell. This hyperpolarizes the cell and makes it more difficult to create a neuronal transmission.
Suppresses RAS and enhances Sleep
↓transmission in sympathetic ganglion
↓post synaptic membrane sensitivity to ACh”
Indication, Onset, E1/2t, protein bound, and Metabolism of Thiopental-TPL?
1) Induction
2) rapid
3) 12 hrs
4) 70% pB
5) CYP450 to hydroxythipental (10-20%), hydroxylation to urine
What are the adverse effects of Thiopental-TPL?
"Vasodilation = reflex tachy Decreased CBF, ICP and CMRO2, Isoelectric EEG Release Histamine = ↑HR and ↓BP Dose dependent Resp depression Pain on injection Decreased threshold for pain Cyp450 inducer N/v"
What are the contraindications of Thiopental-TPL?
“Pregnancy
Porphyria
Asthma”
What is the dosage of Thiopental-TPL?
“3-5mg/kg IV
Decreased dose 30% in first trimester and elderly”
What is the class of Phenobarbital?
“Alkaline – barbituric acid
Phenyl group @carbon #5 = sedative and hypnotic properities, anticonvulsant”
What is the MOA of Phenobarbital?
“Decreases the rate of dissociation from GABA receptor. Increases duration of CL- channel remaining open and allowing Cl- to flow into the cell. This hyperpolarizes the cell and makes it more difficult to create a neuronal transmission.
Suppresses RAS and enhances Sleep
Causes drowsiness and decreases motor activity.”
what is the indication of Phenobarbital?
“Status epilepticus - anticonvulsant
PO for insomnia”
what is the onset, DOA, Peak, E1/2t, and pB of Phenobarbital?
Onset: 5 mins (IV) 20-60mins (PO) DOA= 4-10hrs Peak = 30mins IV E1/2t = 54-170hrs 40%pB
what is the metabolism of Phenobarbital?
Cyp450 hydroxylation and conjugation with 60% unchanged in urine
What are the adverse effects of Phenobarbital?
"Vasodilation = reflex tachy Decreased CBF, ICP and CMRO2, ISO electric EEG Dose dependent Resp depression Pain on injection Decreased threshold for pain Strong Cyp450 inducer N/v Bone marrow suppression Agranulocytosis, thrombocytopenia, megaloblastic anemia Liver toxicity Stevens Johnson syndrome Ataxia **intra arterial injection – can lose limb."
What are the contraindications of Phenobarbital?
“Severe liver disease
Porphyria
Pregnancy
LR=precipitation”
What is dosage of phenobarbital?
“10-20mg/kg, then 5mg/kg q 15-30mins until seizure controlled or max of 30mg/kg reached
Pre op sedation IM 100-200mg 1-1.5hrs pre op
***Most potent hepatic enzyme inducer! – may need more NMB”
What is the class Methohexitol - Brevitol?
“Alkaline – barbturic acid
Methyl radical = convulsant activity”
