Phenobarbital Flashcards Preview

Drug Cards > Phenobarbital > Flashcards

Flashcards in Phenobarbital Deck (14):
1

What is the class of Phenobarbital?

Barbiturate

2

What is Phenobarb used for?

to treat insomnia and preop for sedative effects;
anticonvulsant for acute trtment of partial seizures and tonic-clonic seizures

3

What is the MOA of Phenobarb?

-potentiates GABA
-mimics GABA
-increases influx of Cl- hyperpolarizing the membrane
-depresses the sensory cortex, causes drowsiness/sedation, decreases motor activity

4

How is phenobarb metabolized?

CYP450 inducer and metabolized in liver by hydroxylation and glucuronide conjugation. also excreted unchanged in the urine as high as 60%-90%!!

5

What is the e 1/2 l for phenobarb?

53-140 hours

6

What is the onset for PO? IV? for phenobarb

20-60 min onset PO
5 min IV

7

What is the DOA of phenobarb? PO? IV?

po 6-10 hours
IV 4-10hours

8

IS phenobarb protein bound?

weakly to moderately PB 20-40%

9

What are side effects of Phenobarb?

-BM suppression
-Agranulocytosis
-Thrombocytopenia
-Liver toxicity
-Osteopenia
-Rash
-Stevens-johnson
-apnea
-respiratory depression
- sedation
-insomnia
-hallucinations
-confusion
-dizziness
-n/v

10

What are the contraindications to phenobarb?

-Hypersensitivity to barbs
-resp disease
-dyspnea
-a/w obstruction
-severe liver disease
-porphyria
-pregnancy

11

What are drug interactions with Phenobarb?

they are enzyme inducers! increased metabolism of:
-Phenytoin
-Antiarrhythmics
-anticonvulsants
-antipsychotics
-beta blockers
-CCBs
- Cimetidine
-loop diuretics

12

What are CYP2C19 inducers that would decrease the levels of effectiveness of Phenobarb?

-aminoglutethimide
-Carbamazepine
-phenytoin
-rifampin

13

What is the pre-op sedation dose of phenobarb?

IM 100-200mg 1-1.5hrs before the procedure

14

What is the anticonvulsant loading dose of phenobarb?

10-20mg/kg initially followed by 5 mg/kg q15-30 min until seizure controlled or max dose of 30mg/kg reached