To : Martha
Re : Paxil
From my newest edition out last week. Please note new fields including
Pregnancy risk factors, MW =molecular weight, pKa= equilibrium coef., drug
interactions, Australian, Canadian tradnames, etc. Also, the pediatric
concerns are "Only" those via breastmilk, NOT the direct administration to
the infant.
Regards
Tom Hale, PH.D.
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Paroxetine Fax # 1333
Trade: Paxil
Canadian/Australian: Aropax 20
Uses: Antidepressant, serotonin reuptake inhibitor
AAP: Not reviewed
Paroxetine is a typical serotonin reuptake inhibitor. Although it undergoes
hepatic metabolism, the metabolites are not active. Paroxetine is exceedingly
lipophilic and distributes throughout the body with only 1% remaining in
plasma. In one case report of a mother receiving 20 mg/day paroxetine at
steady state, the breastmilk level at peak (4 hours) was 7.6 µg/L. While
the maternal paroxetine dose was 333 µg/kg, the maximum daily dose to the
infant was estimated at 1.14 µg/kg or 0.34% of the maternal dose.
Pregnancy Risk Category: B
Adult Concerns: Sedation, headache, dry mouth, dizziness, nausea, insomnia,
constipation, seizures.
Pediatric Concerns: Although this product has been occasionally used in
breastfeeding and pregnant women, no reports of untoward effects have been
found.
Drug Interactions: Decreased effect with phenobarbital and phenytoin.
Increased toxicity with alcohol, cimetidine, MAO inhibitors (serotonergic
syndrome). Increased effect with fluoxetine, tricyclic antidepressants,
sertraline, phenothiazines, warfarin.
AHL = 21 hours M/P = 0.09
PHL = PB = 95%
PK = 5-8 hours Oral = Complete
MW = 329 pKa =
Vd = 3-28
References:
1. Pharmaceutical Manufacturers Package Insert, 1996.
2. Kaye CM, Haddock RE, Langley PF et al. a review of the metabolism and
pharmacokinetics of paroxetine in man. Acta Psychiatr Scand 80(Suppl
350):60-75, 1989.
3. Spigset O. Paroxetine level in breast milk. J. Clin Psy. 57(1):39,
1996.
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