This site is intended for healthcare professionals
FDA Hero  Banner - Multi-coloured pills and tablets
FDA Drug information

Phentermine Hydrochloride

Read time: 1 mins
Marketing start date: 14 Apr 2024

Summary of product characteristics


Adverse Reactions

6 ADVERSE REACTIONS 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: Cardiovascular 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. Gastrointestinal Dryness of the mouth, unpleasant taste, diarrhea, constipation, other gastrointestinal disturbances. Allergic Urticaria. Endocrine Impotence, changes in libido. Adverse events have been reported in the cardiovascular, central nervous, gastrointestinal, allergic, and endocrine systems. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Sun Pharmaceutical Industries, Inc. at 1-800-818-4555 or drugsafety@sunpharma.com or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Contraindications

4 CONTRAINDICATIONS History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) During or within 14 days following the administration of monoamine oxidase inhibitors Hyperthyroidism Glaucoma Agitated states History of drug abuse Pregnancy [ see Use in Specific Populations (8.1) ] Nursing [ see Use in Specific Populations (8.3) ] Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) ( 4 ) During or within 14 days following the administration of monoamine oxidase inhibitors ( 4 ) Hyperthyroidism ( 4 ) Glaucoma ( 4 ) Agitated states ( 4 ) History of drug abuse ( 4 ) Pregnancy ( 4 , 8.1 ) Nursing ( 4 , 8.3 ) Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines ( 4 )

Description

11 DESCRIPTION Phentermine hydrochloride USP has the chemical name of α,α,-Dimethylphenethylamine hydrochloride. The structural formula is as follows: Phentermine hydrochloride is a white, odorless, hygroscopic, crystalline powder which is soluble in water and lower alcohols, slightly soluble in chloroform and insoluble in ether. Phentermine hydrochloride, an anorectic agent for oral administration, is available as a tablet containing 37.5 mg of phentermine hydrochloride (equivalent to 30 mg of phentermine base). Phentermine hydrochloride tablets contain the inactive ingredients: crospovidone, dibasic calcium phosphate dihydrate, FD&C Blue #1, magnesium stearate, and povidone. Chemical Structure

Dosage And Administration

2 DOSAGE AND ADMINISTRATION Dosage should be individualized to obtain an adequate response with the lowest effective dose. ( 2 ) Late evening administration should be avoided (risk of insomnia). ( 2 ) Phentermine hydrochloride tablets can be taken with or without food. ( 12.3 ) Exogenous Obesity Dosage should be individualized to obtain an adequate response with the lowest effective dose. The usual adult dose is one tablet (37.5 mg) daily, as prescribed by the physician, administered before breakfast or 1 to 2 hours after breakfast. The dosage may be adjusted to the patient's need. For some patients, half tablet (18.75 mg) daily may be adequate, while in some cases it may be desirable to give half tablets (18.75 mg) two times a day. Phentermine hydrochloride is not recommended for use in pediatric patients ≤ 16 years of age. Late evening medication should be avoided because of the possibility of resulting insomnia.

Indications And Usage

1 INDICATIONS AND USAGE Phentermine hydrochloride is indicated as a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index ≥ 30 kg/m 2 , or ≥ 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia). Below is a chart of body mass index (BMI) based on various heights and weights. BMI is calculated by taking the patient's weight, in kilograms (kg), divided by the patient's height, in meters (m), squared. Metric conversions are as follows: pounds ÷ 2.2 = kg; inches × 0.0254 = meters. The limited usefulness of agents of this class, including phentermine hydrochloride tablets, [ see Clinical Pharmacology (12.1 , 12.2) ] should be measured against possible risk factors inherent in their use such as those described below. Phentermine hydrochloride is a sympathomimetic amine anorectic indicated as a short-term adjunct (a few weeks) in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index ≥ 30 kg/m 2 , or ≥ 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia). ( 1 ) The limited usefulness of agents of this class, including phentermine hydrochloride, should be measured against possible risk factors inherent in their use. ( 1 )

Abuse

9.2 Abuse 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.

Controlled Substance

9.1 Controlled Substance Phentermine is a Schedule IV controlled substance.

Dependence

9.3 Dependence 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 than 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.

Drug Abuse And Dependence

9 DRUG ABUSE AND DEPENDENCE 9.1 Controlled Substance Phentermine is a Schedule IV controlled substance. 9.2 Abuse 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. 9.3 Dependence 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 than 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.

Overdosage

10 OVERDOSAGE The least amount feasible should be prescribed or dispensed at one time in order to minimize the possibility of overdosage. 10.1 Acute 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. 10.2 Chronic Intoxication Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity and personality changes. The most severe manifestation of chronic intoxications is psychosis, often clinically indistinguishable from schizophrenia. See Drug Abuse and Dependence (9.3) .

Drug Interactions

7 DRUG INTERACTIONS Monoamine oxidase inhibitors: Risk of hypertensive crisis. ( 4 , 7.1 ) Alcohol: Consider potential interaction. ( 7.2 ) Insulin and oral hypoglycemics: Requirements may be altered. ( 7.3 ) Adrenergic neuron blocking drugs: Hypotensive effect may be decreased by phentermine. ( 7.4 ) 7.1 Monoamine Oxidase Inhibitors Use of phentermine is contraindicated during or within 14 days following the administration of monoamine oxidase inhibitors because of the risk of hypertensive crisis . 7.2 Alcohol Concomitant use of alcohol with phentermine may result in an adverse drug reaction . 7.3 Insulin and Oral Hypoglycemic Medications Requirements may be altered [ see Warnings and Precautions (5.9) ]. 7.4 Adrenergic Neuron Blocking Drugs Phentermine may decrease the hypotensive effect of adrenergic neuron blocking drugs.

Clinical Pharmacology

12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d / l-amphetamine). Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics." It has not been established that the primary action of such drugs in treating obesity is one of appetite suppression since other central nervous system actions, or metabolic effects, may also be involved. 12.2 Pharmacodynamics Typical actions of amphetamines include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for. 12.3 Pharmacokinetics Following the administration of phentermine, phentermine reaches peak concentrations (C max ) after 3 to 4.4 hours. Specific Populations Renal Impairment Phentermine was not studied in patients with renal impairment. The literature reported cumulative urinary excretion of phentermine under uncontrolled urinary pH conditions is 62% to 85%. Exposure increases can be expected in patients with renal impairment. Use caution when administering phentermine to patients with renal impairment. Drug Interactions In a single-dose study comparing the exposures after oral administration of a combination capsule of 15 mg phentermine and 92 mg topiramate to the exposures after oral administration of a 15 mg phentermine capsule or a 92 mg topiramate capsule, there is no significant topiramate exposure change in the presence of phentermine. However in the presence of topiramate, phentermine C max and AUC increase 13% and 42%, respectively.

Mechanism Of Action

12.1 Mechanism of Action Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d / l-amphetamine). Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics." It has not been established that the primary action of such drugs in treating obesity is one of appetite suppression since other central nervous system actions, or metabolic effects, may also be involved.

Pharmacodynamics

12.2 Pharmacodynamics Typical actions of amphetamines include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.

Pharmacokinetics

12.3 Pharmacokinetics Following the administration of phentermine, phentermine reaches peak concentrations (C max ) after 3 to 4.4 hours. Specific Populations Renal Impairment Phentermine was not studied in patients with renal impairment. The literature reported cumulative urinary excretion of phentermine under uncontrolled urinary pH conditions is 62% to 85%. Exposure increases can be expected in patients with renal impairment. Use caution when administering phentermine to patients with renal impairment. Drug Interactions In a single-dose study comparing the exposures after oral administration of a combination capsule of 15 mg phentermine and 92 mg topiramate to the exposures after oral administration of a 15 mg phentermine capsule or a 92 mg topiramate capsule, there is no significant topiramate exposure change in the presence of phentermine. However in the presence of topiramate, phentermine C max and AUC increase 13% and 42%, respectively.

Effective Time

20220505

Version

5

Dosage Forms And Strengths

3 DOSAGE FORMS AND STRENGTHS Tablets containing 37.5 mg phentermine hydrochloride (equivalent to 30 mg phentermine base). Tablets containing 37.5 mg phentermine hydrochloride. ( 3 )

Spl Product Data Elements

Phentermine Hydrochloride Phentermine Hydrochloride CROSPOVIDONE CALCIUM PHOSPHATE, DIBASIC, DIHYDRATE FD&C BLUE NO. 1 MAGNESIUM STEARATE POVIDONE, UNSPECIFIED PHENTERMINE HYDROCHLORIDE PHENTERMINE with blue specks MP;273

Carcinogenesis And Mutagenesis And Impairment Of Fertility

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility Studies have not been performed with phentermine to determine the potential for carcinogenesis, mutagenesis or impairment of fertility.

Nonclinical Toxicology

13 NONCLINICAL TOXICOLOGY 13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility Studies have not been performed with phentermine to determine the potential for carcinogenesis, mutagenesis or impairment of fertility.

Application Number

ANDA040526

Brand Name

Phentermine Hydrochloride

Generic Name

Phentermine Hydrochloride

Product Ndc

66267-166

Product Type

HUMAN PRESCRIPTION DRUG

Route

ORAL

Package Label Principal Display Panel

pd

Spl Unclassified Section

Regitine ® is a registered trademark of CIBA PHARMACEUTICAL PRODUCTS, INC. Distributed by: Sun Pharmaceutical Industries, Inc. Cranbury, NJ 08512 Rev 12, October 2014

Information For Patients

17 PATIENT COUNSELING INFORMATION Patients must be informed that phentermine hydrochloride is a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity, and that coadministration of phentermine with other drugs for weight loss is not recommended [ see Indications and Usage (1) and Warnings and Precautions (5.1) ]. Patients must be instructed on how much phentermine to take, and when and how to take it [ see Dosage and Administration (2) ]. Advise pregnant women and nursing mothers not to use phentermine [ see Use in Specific Populations (8.1 , 8.3) ]. Patients must be informed about the risks of use of phentermine (including the risks discussed in Warnings and Precautions), about the symptoms of potential adverse reactions and when to contact a physician and/or take other action. The risks include, but are not limited to: -Development of primary pulmonary hypertension [ see Warnings and Precautions (5.2) ] -Development of serious valvular heart disease [ see Warnings and Precautions (5.3) ] -Effects on the ability to engage in potentially hazardous tasks [ see Warnings and Precautions (5.5) ] -The risk of an increase in blood pressure [ see Warnings and Precautions (5.8) and Adverse Reactions (6) ] -The risk of interactions [ see Contraindications (4) , Warnings and Precautions (5.7 , 5.9) and Drug Interactions (7) ] See also, for example, Adverse Reactions (6) and Use in Specific Populations (8) . The patients must also be informed about -the potential for developing tolerance and actions if they suspect development of tolerance [ see Warnings and Precautions (5.4) ] and -the risk of dependence and the potential consequences of abuse [ see Warnings and Precautions (5.6) , Drug Abuse and Dependence (9) , and Overdosage (10) ]. Tell patients to keep phentermine in a safe place to prevent theft, accidental overdose, misuse or abuse. Selling or giving away phentermine may harm others and is against the law.

Clinical Studies

14 CLINICAL STUDIES In relatively short-term clinical trials, adult obese subjects instructed in dietary management and treated with "anorectic" drugs lost more weight on the average than those treated with placebo and diet. The magnitude of increased weight loss of drug-treated patients over placebo-treated patients is only a fraction of a pound a week. The rate of weight loss is greatest in the first weeks of therapy for both drug and placebo subjects and tends to decrease in succeeding weeks. The possible origins of the increased weight loss due to the various drug effects are not established. The amount of weight loss associated with the use of an "anorectic" drug varies from trial to trial, and the increased weight loss appears to be related in part to variables other than the drugs prescribed, such as the physician-investigator, the population treated and the diet prescribed. Studies do not permit conclusions as to the relative importance of the drug and non-drug factors on weight loss. The natural history of obesity is measured over several years, whereas the studies cited are restricted to a few weeks' duration; thus, the total impact of drug-induced weight loss over that of diet alone must be considered clinically limited.

Geriatric Use

8.5 Geriatric Use 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.

Nursing Mothers

8.3 Nursing Mothers It is not known if phentermine 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.

Pediatric Use

8.4 Pediatric Use 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.

Pregnancy

8.1 Pregnancy Teratogenic Effects Pregnancy category X Phentermine 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-amphetamine) [ see Clinical Pharmacology (12.1) ]. 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.

Teratogenic Effects

Teratogenic Effects Pregnancy category X Phentermine 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-amphetamine) [ see Clinical Pharmacology (12.1) ]. 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.

Use In Specific Populations

8 USE IN SPECIFIC POPULATIONS Nursing mothers: Discontinue drug or nursing taking into consideration importance of drug to mother. ( 4 , 8.3 ) Pediatric use: Safety and effectiveness not established. ( 8.4 ) Geriatric use: Due to substantial renal excretion, use with caution. ( 8.5 ) Use caution when administering phentermine to patients with renal impairment. ( 8.6 ) 8.1 Pregnancy Teratogenic Effects Pregnancy category X Phentermine 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-amphetamine) [ see Clinical Pharmacology (12.1) ]. 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. 8.3 Nursing Mothers It is not known if phentermine 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. 8.4 Pediatric Use 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. 8.5 Geriatric Use 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. 8.6 Renal Impairment Phentermine was not studied in patients with renal impairment. Based on the reported excretion of phentermine in urine, exposure increases can be expected in patients with renal impairment. Use caution when administering phentermine to patients with renal impairment [ see Clinical Pharmacology (12.3) ].

How Supplied

16 HOW SUPPLIED/STORAGE AND HANDLING Phentermine hydrochloride tablets USP 37.5 mg (equivalent to 30 mg phentermine base) are white with blue specks, oval shaped, scored on one side and debossed MP 273 on the other side. Bottles of 07 NDC 66267-166-07 Bottles of 14 NDC 66267-166-14 Bottles of 30 NDC 66267-166-30 Bottles of 45 NDC 66267-166-45 Bottles of 60 NDC 66267-166-60 Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature] DISPENSE IN TIGHT, LIGHT-RESISTANT CONTAINER. Keep out of the reach of children.

Storage And Handling

Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature] DISPENSE IN TIGHT, LIGHT-RESISTANT CONTAINER. Keep out of the reach of children.

Learning Zones

The Learning Zones are an educational resource for healthcare professionals that provide medical information on the epidemiology, pathophysiology and burden of disease, as well as diagnostic techniques and treatment regimens.

Disclaimer

The drug Prescribing Information (PI), including indications, contra-indications, interactions, etc, has been developed using the U.S. Food & Drug Administration (FDA) as a source (www.fda.gov).

Medthority offers the whole library of PI documents from the FDA. Medthority will not be held liable for explicit or implicit errors, or missing data.

Drugs appearing in this section are approved by the FDA. For regions outside of the United States, this content is for informational purposes only and may not be aligned with local regulatory approvals or guidance.