Alice -
You asked about Effexor. My '99 edition of Hale says:
"Trade: Effexor
Uses: Antidepressant
AAP: Not reviewed
Venlafaxine is a new serotonin reuptake inhibitor antidepressant. It
inhibits both serontonin reuptake and norepinephrine. Somewhat similar in
mechanism to other antidepressants such as Prozac. Few anticholinergic
side-effects.
In a recent study of three mothers (aged 26, 35, 30 years) receiving
venlafaxine (4.1, 3.0, 8.2 mg/kg), the mean milk/plasma ratio for venlafaxine
(V) was 4.1 (range 3.3-5.2) and O-desmethylvenlafaxine (ODV) was 3.1 (range
2.8-4.0). This mean total infant dose of V was 3.5% (range 3.2-5.2%) and of
ODV (as V equivalents) was 4.1% (range 2.0-5.6) of the maternal
weight-adjusted dose. The combined infant dose in V equivalents was 7.6%
(range 4.7-9.2%). While venlafaxine was not detectable in the infant's
plasma, the metabolite ODV was (median 100ug/L), indicating that the infants
were able to metabolize the drug. Peak milk levels occurred at 2 to 4 hours
with the highest recorded peak levels being 4316 ug/L for V and 3099ug/L for
ODV. While the infants in this study were apparently unaffected, the dose
transferred via milk is relatively high and some caution is urged.
Pregnancy Risk Category: C
Adult Concerns: Nausea/vomiting, somnolence, dry mouth, dizziness, headache,
weakness.
Pediatric concerns: None reported via milk, but no studies are available.
Drug Interactions: Serious, sometimes fatal reactions when used with MAO
inhibitors, or if used with 7-14 days of their use.
T1/2 = 5 hours (venlafaxine)
PK = 2-4 hours
Vd = 6-7
M/P = 3.3-5.2
PB = 27%
Oral = 92%
References: Illett KF, Hackett LP, Dusci LJ, Roverts MH, Kristensen JH, Paech
M, Groves A, and Yapp P. Distribution and excretion of venlafaxine and
O-desmethylvenlafaxine in human milk. Br.J.Clin. Pharmacol. 45:459-462,
1998."
Hope this helps!
Cynthia D. Payne, LLLL, IBCLC
In the Berkshires of western Massachusetts
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