To K.Bruce:
Re: Obese mom whose physician has prescribed Phentermine and Fenfluramine
together.
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Fenfluramine (Pondimin)

Fenfluramine is a sympathmimetic amine structurally similar to amphetamine.
It produces a sustained increase in the levels of serotonin in the brain.
Because of its similarity to amphetamines,  it similarly produces a
short-term anorexia.  However,  depression rather that acute stimulation is
more commonly produced with this product than with ampetamines.  Adverse
effects include dry mouth, fatigue, vivid dreams, drowsiness, diarrhea.
Long term weight loss was minimal, approximately 8% of body weight compared
to 5.5% in placebo groups.

No data is available on the concentrations secreted in breastmilk,  but it
is likely that the milk:plasma ratio would be approximately 1.0 due to its
structure, pKa, and other factors.   Plasma half-life is approximately 20
hours.  Duration of anorexia is only 4-6 hours.  Time to peak is 2-4 hours.
 The average plasma level at steady state is quite low and varies from
40-120 ng/ml.   If the "theoretical" milk:plasma ratio were 1 to 2 which is
likely,  an infant ingesting 1 liter of milk daily would receive less than
0.24 mg/day compared to the maternal dose of 60 mg/day.  (Dextroamphetamine
M:P ratio varies from 2.8 to 7.5).

Fenfluramine is well known to produce dependence, and a significant
withdrawal effect of depression, and sleeplessness, etc. after 6 weeks of
therapy.  A slow withdrawal is probably indicated.

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Phentermine (Ionamin)

Phentermine is an amphetamine analog.  It is well absorbed, and has a
half-life of approximately 20 hours.  It is widely distributed to all
tissues.  No data on transfer to breastmilk is available,  but it is
likely.  Adverse effects include dry mouth, aggitation, irritability,
insomnia, anorexia, stimulation, nausea, vomiting, hypertension, and
physical dependence.



General Statement:

It is likely that after prolonged use,  some stimulation, insomnia,
aggitation, and anorexia could be seen in breastfed infants.  The risk to
the infant could be significant although they have not been reported. Using
these drugs together would be additive,  and tend to enhance the side
effect profile of each.  If these drugs are mandatory for the moms health,
I'm not sure you could justify continued breastfeeding, particularly for a
2 year old.