Phentermine Hcl 30mg Capsules
It is used for weight loss.
Drug Class
Anorexiant
Pharmacologic Class
Sympathomimetic amine, Centrally acting stimulant
Pregnancy Category
Category X
FDA Approved
May 1959
DEA Schedule
Schedule IV
Overview
What is this medicine?
Phentermine is a prescription medication used for short-term weight loss. It works by affecting certain chemicals in your brain to help reduce your appetite. It should be used along with a reduced-calorie diet and increased physical activity.
How to Use This Medicine
Taking Your Medication Correctly
To ensure you get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your medication and follow the instructions closely. The dosage schedule for this medication varies depending on the product. Some products are taken once daily, either before breakfast or 1 to 2 hours after breakfast. Others are taken multiple times a day, 30 minutes before meals. It's essential to understand the specific dosage schedule for your medication.
To minimize potential sleep disturbances, avoid taking this medication late in the evening. If you have any questions or concerns about taking your medication, consult your doctor or pharmacist.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding storage in a bathroom. Keep your medication in a secure location where children cannot see or reach it, and where others cannot access it. Consider using a locked box or area to store your medication. Keep all medications out of reach of pets.
When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless instructed to do so by your pharmacist or healthcare provider. Instead, check with your pharmacist for guidance on the best disposal method. You may also want to explore drug take-back programs in your area.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosage schedule. Do not take two doses at the same time or take extra doses to make up for a missed dose.
To ensure you get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your medication and follow the instructions closely. The dosage schedule for this medication varies depending on the product. Some products are taken once daily, either before breakfast or 1 to 2 hours after breakfast. Others are taken multiple times a day, 30 minutes before meals. It's essential to understand the specific dosage schedule for your medication.
To minimize potential sleep disturbances, avoid taking this medication late in the evening. If you have any questions or concerns about taking your medication, consult your doctor or pharmacist.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding storage in a bathroom. Keep your medication in a secure location where children cannot see or reach it, and where others cannot access it. Consider using a locked box or area to store your medication. Keep all medications out of reach of pets.
When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless instructed to do so by your pharmacist or healthcare provider. Instead, check with your pharmacist for guidance on the best disposal method. You may also want to explore drug take-back programs in your area.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosage schedule. Do not take two doses at the same time or take extra doses to make up for a missed dose.
Lifestyle & Tips
- Follow a reduced-calorie diet as prescribed by your doctor or dietitian.
- Increase your physical activity level as recommended by your healthcare provider.
- Take the medication exactly as prescribed, usually once daily in the morning.
- Do not take phentermine late in the day (e.g., after mid-afternoon) as it can cause insomnia.
- Avoid alcohol while taking this medication.
- Do not stop taking this medication suddenly after prolonged use without consulting your doctor, as withdrawal symptoms may occur.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
30 mg once daily in the morning, before breakfast or 1-2 hours after breakfast
Dose Range:
15 - 37.5 mg
Condition-Specific Dosing:
initialDose:
Start with 15 mg or 30 mg once daily, depending on patient response and tolerability.
durationOfTherapy:
Short-term use (a few weeks) for obesity management, typically not exceeding 12 weeks.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established (Safety and efficacy not established for children under 16 years of age)
Adolescent:
Not established (Safety and efficacy not established for children under 16 years of age)
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment recommended, but use with caution.
Moderate:
Use with caution; consider lower doses (e.g., 15 mg) or extended dosing intervals. Monitor for adverse effects.
Severe:
Contraindicated due to potential for accumulation and increased risk of adverse effects.
Dialysis:
Contraindicated
Hepatic Impairment:
Mild:
No specific adjustment recommended, but use with caution.
Moderate:
Use with caution; consider lower doses. Monitor for adverse effects.
Severe:
Contraindicated due to potential for accumulation and increased risk of adverse effects.
Pharmacology
Mechanism of Action
Phentermine is a sympathomimetic amine with pharmacologic activity similar to amphetamines. It primarily acts as an indirect-acting adrenergic agent, stimulating the release of norepinephrine from nerve terminals in the hypothalamus, particularly in the lateral hypothalamic feeding center. This leads to a reduction in appetite. It also has a minor effect on dopamine and serotonin release. The exact mechanism of its anorectic effect is not fully understood but is thought to involve direct stimulation of the satiety center in the hypothalamus and/or the limbic region.
Pharmacokinetics
Absorption:
Bioavailability:
Not precisely quantified, but well absorbed from the GI tract.
Tmax:
3-4 hours
FoodEffect:
Minimal effect on absorption; can be taken with or without food, but typically recommended before breakfast or 1-2 hours after.
Distribution:
Vd:
Approximately 3.7 L/kg
ProteinBinding:
Approximately 17%
CnssPenetration:
Yes
Elimination:
HalfLife:
19-24 hours (highly dependent on urinary pH; shorter in acidic urine, longer in alkaline urine)
Clearance:
Not precisely quantified, primarily renal.
ExcretionRoute:
Renal (urine)
Unchanged:
60-80% (highly dependent on urinary pH)
Pharmacodynamics
OnsetOfAction:
Approximately 1-2 hours
PeakEffect:
3-4 hours
DurationOfAction:
10-14 hours (due to long half-life, allows for once-daily dosing)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high blood pressure, including:
+ Severe headache
+ Dizziness
+ Passing out
+ Changes in eyesight
Changes in behavior or mood
Shakiness
Heart valve problems or increased pressure in the lungs, which can be life-threatening. If you experience any of the following symptoms, call your doctor right away:
+ Dizziness or passing out
+ Persistent tiredness or weakness
+ Fast or abnormal heartbeat
+ Chest pain
+ Shortness of breath
+ Swelling in your arms or legs
+ Decreased ability to exercise
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or persist, contact your doctor:
Dizziness or headache
Feeling nervous or excitable
Diarrhea or constipation
Dry mouth
Trouble sleeping
Bad taste in your mouth
Decreased interest in sex
Erectile dysfunction
Restlessness
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high blood pressure, including:
+ Severe headache
+ Dizziness
+ Passing out
+ Changes in eyesight
Changes in behavior or mood
Shakiness
Heart valve problems or increased pressure in the lungs, which can be life-threatening. If you experience any of the following symptoms, call your doctor right away:
+ Dizziness or passing out
+ Persistent tiredness or weakness
+ Fast or abnormal heartbeat
+ Chest pain
+ Shortness of breath
+ Swelling in your arms or legs
+ Decreased ability to exercise
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or persist, contact your doctor:
Dizziness or headache
Feeling nervous or excitable
Diarrhea or constipation
Dry mouth
Trouble sleeping
Bad taste in your mouth
Decreased interest in sex
Erectile dysfunction
Restlessness
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe chest pain
- Shortness of breath, especially with exertion
- Fainting spells
- Swelling in your legs or ankles
- Rapid or irregular heartbeat
- Severe headache
- Blurred vision
- Unusual changes in mood or behavior (e.g., severe anxiety, agitation, hallucinations)
- Signs of allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing)
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following conditions and situations to ensure safe treatment:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reaction and its symptoms.
A history of heart disease, including heart failure or abnormal heart rhythms, as well as high blood pressure or stroke.
Presence of glaucoma, agitation, anxiety, or an overactive thyroid gland.
Kidney disease or being on dialysis.
Recent use (within the last 14 days) of certain medications for depression or Parkinson's disease, such as isocarboxazid, phenelzine, tranylcypromine, selegiline, or rasagiline, as this can lead to severely high blood pressure.
Current use of fluoxetine, fluvoxamine, linezolid, methylene blue, paroxetine, or sertraline, as these can interact with this medication.
Use of any other weight loss medications, whether prescription, over-the-counter, or natural products.
Pregnancy or potential pregnancy, as this medication should not be taken during pregnancy.
* Breast-feeding, as you should not breast-feed while taking this medication.
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist. They will help determine if it is safe to take this medication with your other treatments and health issues. Never start, stop, or adjust the dosage of any medication without consulting your doctor first.
It is essential to inform your doctor about the following conditions and situations to ensure safe treatment:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reaction and its symptoms.
A history of heart disease, including heart failure or abnormal heart rhythms, as well as high blood pressure or stroke.
Presence of glaucoma, agitation, anxiety, or an overactive thyroid gland.
Kidney disease or being on dialysis.
Recent use (within the last 14 days) of certain medications for depression or Parkinson's disease, such as isocarboxazid, phenelzine, tranylcypromine, selegiline, or rasagiline, as this can lead to severely high blood pressure.
Current use of fluoxetine, fluvoxamine, linezolid, methylene blue, paroxetine, or sertraline, as these can interact with this medication.
Use of any other weight loss medications, whether prescription, over-the-counter, or natural products.
Pregnancy or potential pregnancy, as this medication should not be taken during pregnancy.
* Breast-feeding, as you should not breast-feed while taking this medication.
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist. They will help determine if it is safe to take this medication with your other treatments and health issues. Never start, stop, or adjust the dosage of any medication without consulting your doctor first.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
When starting this medication, be cautious and avoid driving or engaging in activities that require alertness until you understand how it affects you.
Adhere to your doctor's prescribed dosage and treatment duration. Do not exceed the recommended duration or dosage, as prolonged use or high doses can lead to tolerance, reducing the medication's effectiveness. If you experience a decrease in the medication's effectiveness, consult your doctor. Avoid taking more than the prescribed amount.
If you have been taking this medication for an extended period, consult your doctor before discontinuing its use. Your doctor may recommend a gradual tapering off the medication to minimize potential withdrawal effects. Be aware that this medication can be habit-forming, and long-term use should be avoided. If you have a history of drug or alcohol abuse, inform your doctor.
Before initiating treatment, your doctor may require you to undergo certain heart tests. If you have any questions or concerns, discuss them with your doctor. Regularly monitor your blood pressure and heart rate as instructed by your doctor.
If you have diabetes and are taking medications to lower your blood sugar, consult your doctor. Weight loss associated with this medication may increase the risk of hypoglycemia (low blood sugar) in individuals taking blood sugar-lowering medications. Be aware of the signs of hypoglycemia, which include dizziness, headache, drowsiness, weakness, shaking, rapid heartbeat, confusion, hunger, and sweating. If you experience any of these symptoms, contact your doctor immediately.
Follow the diet and exercise plan recommended by your doctor. Additionally, consult your doctor before consuming alcohol while taking this medication.
This medication is not intended for children under the age of 17.
When starting this medication, be cautious and avoid driving or engaging in activities that require alertness until you understand how it affects you.
Adhere to your doctor's prescribed dosage and treatment duration. Do not exceed the recommended duration or dosage, as prolonged use or high doses can lead to tolerance, reducing the medication's effectiveness. If you experience a decrease in the medication's effectiveness, consult your doctor. Avoid taking more than the prescribed amount.
If you have been taking this medication for an extended period, consult your doctor before discontinuing its use. Your doctor may recommend a gradual tapering off the medication to minimize potential withdrawal effects. Be aware that this medication can be habit-forming, and long-term use should be avoided. If you have a history of drug or alcohol abuse, inform your doctor.
Before initiating treatment, your doctor may require you to undergo certain heart tests. If you have any questions or concerns, discuss them with your doctor. Regularly monitor your blood pressure and heart rate as instructed by your doctor.
If you have diabetes and are taking medications to lower your blood sugar, consult your doctor. Weight loss associated with this medication may increase the risk of hypoglycemia (low blood sugar) in individuals taking blood sugar-lowering medications. Be aware of the signs of hypoglycemia, which include dizziness, headache, drowsiness, weakness, shaking, rapid heartbeat, confusion, hunger, and sweating. If you experience any of these symptoms, contact your doctor immediately.
Follow the diet and exercise plan recommended by your doctor. Additionally, consult your doctor before consuming alcohol while taking this medication.
This medication is not intended for children under the age of 17.
Overdose Information
Overdose Symptoms:
- Restlessness
- Tremor
- Hyperreflexia
- Rapid breathing
- Confusion
- Assaultiveness
- Hallucinations
- Panic states
- High fever
- Rhabdomyolysis
- Arrhythmias
- Hypertension or hypotension
- Circulatory collapse
- Nausea
- Vomiting
- Diarrhea
- Abdominal cramps
- Convulsions
- Coma
What to Do:
Seek immediate medical attention. Call 911 or your local emergency number. For poison control, call 1-800-222-1222.
Drug Interactions
Contraindicated Interactions
- Monoamine Oxidase Inhibitors (MAOIs) - concurrent use or within 14 days of MAOI discontinuation (risk of hypertensive crisis)
- Other centrally acting appetite suppressants (e.g., fenfluramine, dexfenfluramine, sibutramine) - risk of primary pulmonary hypertension and/or valvular heart disease
- Alcohol (concurrent use)
Major Interactions
- Serotonergic drugs (e.g., SSRIs, SNRIs, TCAs, triptans, fentanyl, tramadol, St. John's Wort) - risk of serotonin syndrome
- Other sympathomimetic agents (e.g., decongestants like pseudoephedrine, phenylephrine; other stimulants) - additive cardiovascular effects (hypertension, arrhythmias)
- Antihypertensive agents (e.g., guanethidine, clonidine, methyldopa) - phentermine may antagonize their hypotensive effects
- Insulin and oral hypoglycemic agents - phentermine may alter blood glucose levels, requiring dosage adjustment of antidiabetic medications
Moderate Interactions
- Urinary alkalinizers (e.g., sodium bicarbonate, acetazolamide) - may increase phentermine half-life and duration of action, increasing risk of toxicity
- Urinary acidifiers (e.g., ammonium chloride, ascorbic acid) - may decrease phentermine half-life and duration of action, reducing efficacy
- Caffeine - additive stimulant effects
Minor Interactions
- Not available
Monitoring
Baseline Monitoring
Blood Pressure (BP)
Rationale: Phentermine can cause an increase in blood pressure.
Timing: Prior to initiation of therapy
Heart Rate (HR)
Rationale: Phentermine can cause tachycardia and palpitations.
Timing: Prior to initiation of therapy
Weight
Rationale: To establish baseline and monitor efficacy.
Timing: Prior to initiation of therapy
Medical History (especially cardiovascular, psychiatric, thyroid disorders)
Rationale: To identify contraindications or conditions requiring caution.
Timing: Prior to initiation of therapy
Routine Monitoring
Blood Pressure (BP)
Frequency: Regularly throughout therapy (e.g., weekly for first few weeks, then monthly)
Target: Maintain within normal limits or patient's target range
Action Threshold: Discontinue if sustained significant increase in BP occurs
Heart Rate (HR)
Frequency: Regularly throughout therapy (e.g., weekly for first few weeks, then monthly)
Target: Maintain within normal limits or patient's target range
Action Threshold: Discontinue if sustained significant tachycardia or arrhythmias occur
Weight
Frequency: Weekly to monthly
Target: Consistent weight loss (e.g., 1-2 lbs/week)
Action Threshold: Lack of adequate weight loss after 4-12 weeks may warrant discontinuation
Symptoms of Pulmonary Hypertension (e.g., dyspnea, chest pain, syncope, lower extremity edema)
Frequency: At each visit
Target: Absence of symptoms
Action Threshold: Promptly discontinue if symptoms develop and investigate
Mental Status/Psychiatric Symptoms (e.g., agitation, insomnia, anxiety, mood changes)
Frequency: At each visit
Target: Stable mood and behavior
Action Threshold: Discontinue if severe psychiatric symptoms or psychosis develop
Symptom Monitoring
- Chest pain
- Shortness of breath (dyspnea)
- Fainting (syncope)
- Swelling in legs/ankles (lower extremity edema)
- Palpitations
- Dizziness
- Insomnia
- Nervousness
- Agitation
- Dry mouth
- Constipation
- Tremor
- Headache
Special Patient Groups
Pregnancy
Contraindicated (Category X). Phentermine is not indicated for use during pregnancy. Weight loss during pregnancy offers no potential benefit to the pregnant woman and may result in fetal harm. A minimum weight gain, and often more, is currently recommended for all pregnant women, including those who are already overweight or obese, because of the obligatory weight gain that occurs in maternal tissues during pregnancy.
Trimester-Specific Risks:
First Trimester:
Potential for fetal harm; not studied.
Second Trimester:
Potential for fetal harm; not studied.
Third Trimester:
Potential for fetal harm; not studied.
Lactation
Contraindicated (L5). It is not known whether phentermine is excreted in human milk. Due to the potential for serious adverse reactions in the nursing infant (e.g., irritability, sleep disturbances, poor feeding, cardiovascular effects), phentermine is not recommended during breastfeeding. The drug's indication for weight loss is also generally inappropriate during lactation.
Infant Risk:
High risk of serious adverse effects; unknown excretion into milk but potential for stimulant effects.
Pediatric Use
Safety and efficacy have not been established in pediatric patients under 16 years of age. Use is generally not recommended.
Geriatric Use
Use with caution in elderly patients (65 years and older). Elderly patients may be more sensitive to the effects of sympathomimetic amines, particularly cardiovascular and central nervous system effects. Consider starting with lower doses and titrating slowly, and monitor closely for adverse reactions.
Clinical Information
Clinical Pearls
- Phentermine is intended for short-term use (typically 3-6 weeks, up to 12 weeks) as an adjunct to a comprehensive weight management program.
- It should not be used in patients with a history of cardiovascular disease (e.g., uncontrolled hypertension, arrhythmias, heart failure, stroke), hyperthyroidism, glaucoma, or a history of drug abuse.
- Patients should be advised about the potential for dependence and withdrawal symptoms if discontinued abruptly after prolonged use.
- Monitor for signs and symptoms of primary pulmonary hypertension, a rare but serious adverse effect.
- Avoid late evening dosing to prevent insomnia.
- Combination with other weight loss drugs (especially serotonergic agents) is generally not recommended due to increased risk of adverse effects.
Alternative Therapies
- Liraglutide (Saxenda, Victoza)
- Semaglutide (Wegovy, Ozempic)
- Orlistat (Xenical, Alli)
- Naltrexone/Bupropion (Contrave)
- Diethylpropion
- Phendimetrazine
Cost & Coverage
Average Cost:
Varies widely, typically $15-$50 per 30 capsules (30mg)
Generic Available:
Yes
Insurance Coverage:
Tier 2 or Tier 3 (often requires prior authorization or step therapy for weight loss medications)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide information about the medication taken, the amount, and the time it happened.