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secobarbital (Seconal)
Tradename: Seconal. DEA-controlled substance: class 2.
Indications:
1) agitation
2) insomnia
3) general anesthesia, induction of sedation
4) status epilepticus
5) tetanus
6) neuroprotection???
Contraindications:
1) absolute: barbiturate hypersensitivity
2) relative
-> breast feeding, children, CNS depression, depression, driving or operating machinery, elderly, hypotension, mental status changes, pain, porphyria, pregnancy, pulmonary disease, renal impairment, status asthmaticus, substance abuse, suicidal ideation
Dosage:
1) 100 mg PO
2) 100-200 mg IM
3) IV 50 mg/min up to 250 mg; additional doses every 5min; max 500 mg
Do not abruptly discontinue
Tabs: 100 mg.
Pharmacokinetics:
1) food interferes with absorption
2) peak plasma levels reached in 2-4 hours after oral administration
3) pharmacologic response within 15 minutes of oral dose
4) duration of hypnotic effect
a) 1-4 hours following oral dose
b) 15 minutes following IV dose
5) loses hypnotic effect after 2 weeks of administration
6) protein binding 30-45%
7) metabolism via liver to inactive metabolites
8) eliminated in urine as metabolites & their glucuronide conjugates
9) elimination 1/2life is about 30 hours
Adverse effects:
1) sedation
2) respiratory arrest
3) coma
4) others
-> hypotension, impotence, maculopapular rash, miosis, mydriasis, nausea/vomiting, nystagmus, osteopenia, phlebitis, photosensitivity, dependence, ptosis, purpura, sinus bradycardia, Stevens-Johnson syndrome, thrombocytopenia, toxic epidermal necrolysis, urticaria, withdrawal
Drug interactions:
1) coadministration of valproic acid may increase plasma barbiturate levels
2) barbiturates induce CYP1A2, CYP2C9 & CYP3A4
-> may diminish levels of drugs metabolized by CYP1A2, CYP2C9 & CYP3A4
3) secobarbital decreases acetaminophen effectiveness; may increase toxic metabolites with acetaminophen overdose
4) valproate may inhibit metabolism of secobarbital
5) most data for drug interactions is for phenobarbital
Laboratory:
1) specimen: serum; stable refrigerated or frozen
2) methods: color, GLC, HPLC, RIA, EIA
3) interferences: spectrophometric assay are subject to numerous interferences, but are useful emergency procedures
Mechanism of action:
1) suppresses seizure activity in cortex, thalamus & limbic system
2) inhibition of both pre- & postsynaptic excitability
3) protects brain from ischemia & intracranial pressure (high doses)
Interactions
drug interactions
drug adverse effects (more general classes)
Related
cytochrome p450 1A2 (cytochrome P3-450, phenacetin deethylase, cytochrome p450-4, CYP1A2)
cytochrome P450 2C9; cytochrome P450 BP-1; cytochrome P450 MP-4; S-mephenytoin-4-hydroxylase; limonene 6-monooxygenase; limonene 7-monooxygenase (CYP2C9, CYP2C10)
cytochrome P450 3A4 (cytochrome P450 C3, nifedipine oxidase, P450-PCN1, NF-25, CYP3A4)
General
barbiturate
sedative/hypnotic (tranquilizer)
Properties
MISC-INFO: elimination route LIVER
1/2life 19-34 HOURS
therapeutic-range 1-2 UG/ML
toxic-range >5 UG/ML
protein-binding 26-45%
pregnancy-category D
safety in lactation ?
Database Correlations
PUBCHEM correlations
References
- Clinical Guide to Laboratory Tests, 3rd edition, NW Tietz
ed, WB Saunders, Philadelphia, 1995
- The Pharmacological Basis of Therapeutics, 9th ed.
Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- Clinical Guide to Laboratory Tests, NW Tietz (ed) 3rd ed,
WB Saunders, Philadelpha 1995
- Prescriber's Letter 13(3): 2006
Cytochrome P450 drug interactions
Detail-Document#: 220233
(subscription needed) http://www.prescribersletter.com
- Harrison's Online, 2002
Component-of
amobarbital/secobarbital (Tuinal)