II. Indications
- Physician discretion for indication to continue
- Short term (8 to 12 weeks per year) adjunctive Obesity Management
III. Contraindications
- MAO Inhibitors within 14 days (see Drug Interactions below)
- Creatinine Clearance <15 ml/min
- Substance Use Disorder
- Hyperthyroidism
- Glaucoma
- Agitated state
- Pregnancy or Lactation
- Cardiovascular disease
IV. Precautions
- Individualize dosing to the lowest effective amount
- Tolerance to Phentermine may occur within weeks (at which point it does not suppress appetite)
- Discontinue if tolerance develops and do not exceed maximum Phentermine dose
-
DEA Controlled Substance
- Class IV (Limited dependence liability)
V. Mechanism
- Sympathomimetic amine anorectic
- Stimulates CNS adrenergic system
- Reduces food seeking behavior
VI. Medications
- Phentermine
- Capsules: 15, 30, 37.5 mg
- Tablets: 37.5 mg
- ODT Tablets: 15, 30, 37.5 mg
- Lomaira Tablets: 8 mg
- Combinations
- Qsymia (Phentermine and Topiramate)
- Phentermine is also often combined with Fluoxetine 20 mg as an alternative to Topiramate
VII. Dosing
- Not FDA approved for age <16 years
- Phentermine Tablets (18.75 or 37.5 mg)
- Start 18.75 mg orally at 1-2 hours before breakfast
- Titrate to 18.75 mg orally twice daily OR 37.5 mg orally once daily
- Phentermine Capsules (15 or 30 mg)
- Start 15 mg orally at 2 hours before breakfast
- Titrate to 30 mg orally daily
- Lomaira: 8 mg orally three times daily at 30 min before meals
- May decrease to 4 mg orally three times daily for tolerability if effective
-
Renal Dosing
- Creatinine Clearance 15 to 29 ml/min: Max Phentermine Dose 15 mg/day
- Creatinine Clearance <15 ml/min: Avoid Phentermine
VIII. Pharmacokinetics
- Phentermine hydochloride absorption is not affected by food (may taken with or without food)
- Peak concentration reached at 3 to 4.4 hours after oral dose
IX. Adverse Effects
-
Agitation
- Intolerable in 11%
-
Insomnia
- Avoid dosing late in the day
- Dose at least 10 hours before sleep
-
Substance Abuse risk
- Phentermine is related to Amphetamines
- Rare (but serious)
- Primary Pulmonary Hypertension
- Regurgitant cardiac valvular disease
X. Safety
- Pregnancy Category X
- Avoid in Lactation
XI. Drug Interactions
-
MAO Inhibitors
- Associated with Hypertensive Crisis (do not use with Phentermine within 14 days)
-
Insulin and Oral Hypoglycemics
- Monitor Glucose (dosing adjustments may be needed)
XII. Efficacy
- See Obesity Medication
- Weight Loss
- Results in 5 pound weight loss more than Placebo in one year
XIII. Resources
- Phentermine hydochloride (DailyMed)
XIV. References
- Hamilton (2020) Tarascon Pharmacopoeia
Images: Related links to external sites (from Bing)
Related Studies
| phentermine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| PHENTERMINE 15 MG CAPSULE | Generic | $0.13 each |
| PHENTERMINE 30 MG CAPSULE | Generic | $0.14 each |
| PHENTERMINE 37.5 MG CAPSULE | Generic | $0.11 each |
| PHENTERMINE 37.5 MG TABLET | Generic | $0.07 each |
| lomaira (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| LOMAIRA 8 MG TABLET | Generic | $0.52 each |
Ontology: Phentermine (C0031447)
| Definition (NCI) | A natural monoamine alkaloid derivative and a sympathomimetic stimulant with appetite suppressant property. Phentermine, which was part of the Fen-Phen anti-obesity medication, stimulates hypothalamic release of norepinephrine, a neurotransmitter involved in stress responses (fight-or-flight reactions), and reduces hunger sensation. Phentermine also causes the release of epinephrine or adrenaline outside of the brain, resulting in breakdown of stored fat. |
| Definition (MSH) | A central nervous system stimulant and sympathomimetic with actions and uses similar to those of DEXTROAMPHETAMINE. It has been used most frequently in the treatment of obesity. |
| Definition (CSP) | central nervous system stimulant and sympathomimetic with actions and uses similar to dextroamphetamine; used in the treatment of obesity. |
| Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
| MSH | D010645 |
| SnomedCT | 373343009, 53480001 |
| LNC | LP16250-0, MTHU006735 |
| English | Phentermine, Benzeneethanamine, alpha,alpha-dimethyl-, phentermine, Phentermine [Chemical/Ingredient], 1,1-Dimethyl-2-phenylethylamine, 2-Phenyl-tert-butylamine, 2-Amino-2-methyl-1-phenylpropane, PHENTERMINE, Phenyl-tertiary-butylamine, Phentermine (product), Phentermine (substance) |
| Swedish | Fentermin |
| Czech | fentermin |
| Finnish | Fentermiini |
| Russian | FENTERMIN, ФЕНТЕРМИН |
| Japanese | フェンテルミン, フェンテルミン塩酸塩, デュロミン, 塩酸フェンテルミン, イオナミン |
| Polish | Fentermina |
| Spanish | fentermina (producto), fentermina (sustancia), fentermina, Fentermina |
| French | Phentermine |
| German | Phentermin |
| Italian | Fentermina |
| Portuguese | Fentermina |
