QUICKLINKS AND VIEW OPITONS
Phentermine: Drug interactions
Friday, May 07, 2004 2:40 pm Email this article
People taking the following medications should not take phentermine because of possible drug interactions unless instructed to do so by your physician.
People taking the following medications should not take phentermine because of possible drug interactions.
Phentermine should not be taken with monoamine oxidase (MAO) inhibitors or within 14 days of stopping treatment with MAO inhibitors.
Phentermine can interact with MAO inhibitors to cause hypertensive crisis (dangerously high blood pressure).
MAO inhibitors are a group of drugs used to treat depression, anxiety (especially anxiety associated with phobias), migraine headaches, and hypertension (high blood pressure).
Common MAO inhibitors include: isocarboxazid (Marplan), phenelzine (Nardil), selegiline (Eldepryl), tranylcypromine (Parnate).
Phentermine should not be used with alcohol because of possible dangerous drug interactions.
Phentermine may alter insulin requirements in insulin-dependent diabetics.
FURAZOLIDONE (antibacterial agent)
Phentermine should not be used with the antibacterial agent furazolidone (Furoxone). Furazolidone has been shown to have MAO inhibition activity and if combined with phentermine could result in dangerously high blood pressure.
GUANETHIDINE (blood pressure medicine)
Phentermine may reduce the effects of the high blood pressure medication guanethidine and should not be used together.
Common brands containing guanethidine include: Esimil and Ismelin.
Lithium may antagonize (oppose) the effects of phentermine.15
a-Methyltyrosine (a high blood pressure medication) may antagonize (oppose) the effects of phentermine.15 Medications containing a-methyltyrosine include: Demser.
Please note that many physicians are successfully using a combination of phentermine with Prozac and other serotonin reuptake inhibitors to help people lose weight.
However, there is at least one report of an apparent interaction with this combination to be aware of.
Bostwick and Brown (1996) describe a drug interaction between phentermine and Prozac.
A 22-year-old woman was given 20 mg of Prozac per day for three months to treat a major depression.
Previously she had taken phentermine (30 mg per day) intermittently to control her weight without difficulty, but had stopped entirely before starting on Prozac.
Eight days after stopping the Prozac she took one 30-mg tablet of phentermine.
Within several hours she was in her psychiatrist’s office complaining of feeling “jittery; everything’s in fast motion.”
She said her thoughts were “going too fast… They keep skipping back and forth… I don’t have time to finish my sentences.”
She also complained of stomach cramps, dry eyes, palpitations, and tremors.
Her blood pressure was 125/88; her pulse was 84.
She was prescribed three 0.5 mg tablets of lorazepam (Ativan) to be taken that evening.
The next morning her complaints had resolved entirely.
Her blood pressure was 132/76; her pulse was 76.
She noted that the symptoms began to resolve with the first 0.5 mg of lorazepam and resolved completely after taking another 1 mg.
Bostwick and Brown (1996) reasoned that the best explanation for this interaction was due to Prozac’s inhibition of cytochrome P-450 which would increase blood levels of phentermine.
Bostwick J, Brown T. A toxic reaction from combining fluoxetine and phentermine. J Clin Psychopharmacol. 1996 Apr, 16(2):189-90.
Articles on the same subject can be found here:
Please feel free to share your comments about this article.
© Copyright 2003-2021 - Larry Hobbs - All Rights Reserved.