Phentermine 381developing primary pulmonary hypertension, a major and often fatal affliction
involving blood circulation through the lungs. The drug is not recommended
for persons with heart ailment, serious hardening of the arteries, high blood
pressure, glaucoma, or an overactive thyroid gland. The drug may impair
ability to operate tools and machinery, such as automobiles.
Someone taking phentermine came down with a psychosis that cleared up
after stopping the drug. Initially the affliction was blamed on the drug, but
the person later developed paranoid schizophrenia, a development suggesting
that the drug promoted but did not cause the initial psychosis. The incident
did not demonstrate that phentermine will cause psychosis in healthy people.
With someone else, symptoms mimicking schizophrenia appeared when dos-
age of phentermine increased and stopped after ingestion of phentermine
stopped. In another case a user began seeing people appear and vanish, heard
things no one else could perceive, and started experiencing paranoia—afflic-
tions attributed to the drug. Such reports became numerous enough that prac-
titioners were advised to limit the drug’s use to only a few weeks. Adverse
psychological reactions are a known hazard of overdose. Physicians have pub-
licly cautioned against exceeding recommended dosage and against prescrib-
ing to persons with personal or family histories of mental illness.
Abuse factors.Research is uncommon on phentermine’s specific tolerance,
dependence, withdrawal, and addiction potentials, but such factors are prob-
ably similar to those of stimulants in general. Animal and human experiments
suggest that phentermine may help cocaine addicts decrease their use of the
latter drug.
Drug interactions.Because of phentermine’s possible MAOI properties it
should normally be avoided if a patient is taking some other MAOI, and it
may have untoward effect ifalcoholbeverages are consumed.
For years “fen-phen” was a widely prescribed weight reduction combina-
tion of phentermine and fenfluramine. In 1997 controversy arose about
whether the combination caused serious and sometimes fatal heart disease;
for details see this book’s entry about fenfluramine. Heart disease has been
reported following use of phentermine with other drugs as well and, more
rarely, without taking any other drugs. In contrast, one practitioner who
treated hundreds of patients with phentermine found no evidence of cardiac
disease caused by the drug used alone or in combination with the antide-
pressant fluoxetine (Prozac). That latter “phen-pro” combination has been re-
ported as causing adverse reaction similar to amphetamine overdose, but such
reports are uncommon.
Cancer.Not enough scientific information to report.
Pregnancy.Researchers seeking evidence of human birth defects report that
standard medical usage in the first trimester found none attributable to the
drug.
Additional information.Adipex-P and Fastin are the slightly less potent
hydrochloride form of the substance (30 mg of phentermine hydrochloride
roughly equals 24 mg of phentermine). The potential for causing cancer or
birth defects is unestablished. This form may enter human milk if nursing
mothers take the drug.
Additional scientific information may be found in: