A reduction in insulin or oral hypoglycemic medications in patients with diabetes mellitus may be required.
The following adverse reactions are described, or described in greater detail, in other sections:
- Primary pulmonary hypertension [ see Warnings and Precautions ( 5.2) ]
- Valvular heart disease [ see Warnings and Precautions ( 5.3) ]
- Effect on the ability to engage in potentially hazardous tasks [ see Warnings and Precautions ( 5.5) ]
- Withdrawal effects following prolonged high dosage administration [ see Drug Abuse and Dependence ( 9.3) ]
The following adverse reactions to phentermine have been identified:
Primary pulmonary hypertension and/or regurgitant cardiac valvular disease, palpitation, tachycardia, elevation of blood pressure, ischemic events.
Central Nervous System
Overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, psychosis.
Dryness of the mouth, unpleasant taste, diarrhea, constipation, other gastrointestinal disturbances.
Impotence, changes in libido.
Use of ADIPEX-P ® is contraindicated during or within 14 days following the administration of monoamine oxidase inhibitors because of the risk of hypertensive crisis.
Concomitant use of alcohol with ADIPEX-P ® may result in an adverse drug reaction.
Requirements may be altered [ see Warnings and Precautions ( 5.9) ].
ADIPEX-P ® may decrease the hypotensive effect of adrenergic neuron blocking drugs.
® is contraindicated during pregnancy because weight loss offers no potential benefit to a pregnant woman and may result in fetal harm. A minimum weight gain, and no weight loss, is currently recommended for all pregnant women, including those who are already overweight or obese, due to obligatory weight gain that occurs in maternal tissues during pregnancy. Phentermine has pharmacologic activity similar to amphetamine (d- and d
l l-amphetamine) [
see Clinical Pharmacology (
]. Animal reproduction studies have not been conducted with phentermine. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus.
It is not known if ADIPEX-P ® is excreted in human milk; however, other amphetamines are present in human milk. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness in pediatric patients have not been established. Because pediatric obesity is a chronic condition requiring long-term treatment, the use of this product, approved for short-term therapy, is not recommended.
In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.
Based on the reported excretion of phentermine in urine, exposure increases can be expected in patients with renal impairment [ see Clinical Pharmacology ( 12.3) ].
Use caution when administering ADIPEX-P ® to patients with renal impairment. In patients with severe renal impairment (eGFR 15 to 29 mL/min/1.73 m 2), limit the dosage of ADIPEX-P ® to 15 mg daily [ see Dosage and Administration ( 2.2) ]. ADIPEX-P ® has not been studied in patients with eGFR less than 15 mL/min/1.73 m 2 , including end-stage renal disease requiring dialysis; avoid use in these populations.
Phentermine is a Schedule IV controlled substance.
Phentermine is related chemically and pharmacologically to the amphetamines. Amphetamines and other stimulant drugs have been extensively abused and the possibility of abuse of phentermine should be kept in mind when evaluating the desirability of including a drug as part of a weight reduction program.
Abuse of amphetamines and related drugs may be associated with intense psychological dependence and severe social dysfunction. There are reports of patients who have increased the dosage of these drugs to many times that recommended. Abrupt cessation following prolonged high dosage administration results in extreme fatigue and mental depression; changes are also noted on the sleep EEG. Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity and personality changes. A severe manifestation of chronic intoxication is psychosis, often clinically indistinguishable from schizophrenia.
The least amount feasible should be prescribed or dispensed at one time in order to minimize the possibility of overdosage.
Manifestations of acute overdosage include restlessness, tremor, hyperreflexia, rapid respiration, confusion, assaultiveness, hallucinations, and panic states. Fatigue and depression usually follow the central stimulation. Cardiovascular effects include tachycardia, arrhythmia, hypertension or hypotension, and circulatory collapse. Gastrointestinal symptoms include nausea, vomiting, diarrhea and abdominal cramps. Overdosage of pharmacologically similar compounds has resulted in fatal poisoning usually terminates in convulsions and coma.
Management of acute phentermine hydrochloride intoxication is largely symptomatic and includes lavage and sedation with a barbiturate. Experience with hemodialysis or peritoneal dialysis is inadequate to permit recommendations in this regard. Acidification of the urine increases phentermine excretion. Intravenous phentolamine (Regitine ® , CIBA) has been suggested on pharmacologic grounds for possible acute, severe hypertension, if this complicates overdosage.
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