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Phentermine Facts

Stimulant; Substituted amphetamine; Norepinephrine releasing agent

Description

Phentermine (2-methyl-1-phenylpropan-2-amine) is a synthetic stimulant of the phenethylamine class. It releases norepinephrine — the brain's alertness signal — flooding appetite-control centers in the brain and producing a flat, sustained stimulation.[1]

Subjective effects include appetite suppression, wakefulness, mild mood elevation, and low-level psychomotor activation. The experience is functional rather than euphoric — a sustained, flat stimulation without the rewarding rush of potent dopamine releasers.[2]

Dependence liability is low — stopping abruptly does not produce cravings or amphetamine-like withdrawal.[3] The primary danger is cardiovascular: phentermine raises heart rate and blood pressure, and combining it with MAOIs can trigger a potentially fatal blood pressure crisis.[4]

Dose and durationby route · individual sensitivity varies

Oral(mg)
Threshold< 8 mgLight8 – 15 mgCommon15 – 37.5 mgStrong37.5 – 37.5 mgHeavynot recorded

Starts in 30 – 60 minLasts 8 – 14 hoursAfter-effects 12 – 24 hours

Body and dependence

Acute toxicity
Moderate
Chronic toxicity
Moderate
Physical dependence
Negligible
Psychological dependence
Low
Withdrawal
None recorded
Compulsive redosing
Low

Tolerance

Builds
Rapid
Fully resets after
Not recorded
Carries over to
amphetamine; methamphetamine; MDMA

Effectslikely at a common dose

Perception
none likely · 1 possible
Body
Appetite suppression; Stimulation; Vasoconstriction; Wakefulness; +14 possible, including Abnormal heartbeat, Insomnia, Heart rate perception changes
Thinking
none likely · 4 possible
Feeling
none likely · 3 possible, including Anxiety
Self
none likely · 4 possible, including Craving
Awareness
Sustained attention (vicara); +1 possible

Who shouldn't take it

Absolute
Cardiovascular disease; Agitated states; History of drug abuse; Hyperthyroidism; Sympathomimetic amine hypersensitivity; Pregnancy; Lactation; MAOI use (within 14 days); Glaucoma

Combinations60 recorded

Lethal (1)
MAOIs
Dangerous (28)
Alpha-2 adrenergic receptor antagonist; Anticholinergics; Caffeine; Ephedrine, Pseudoephedrine; GHB, Baclofen; Local anesthetics; MDMA, Amphetamines; MDMA, MDA; NDRIs (Wellbutrin); NRIs; Opioids; SNRIs; SSRIs; Stimulants; 5-HTP, Tryptophan; Antipsychotics; Buspirone; Dopamine agonists; DXM; GHB, GBL; Ibogaine; Ketamine, DXM, PCP; Lithium; NSAIDs; and 4 more, see full page
Caution (28)
See full page: psychedex.org/substances/phentermine
Not graded (3)
Not listed never means safe.

Seek help immediately if

  • Chest pain; racing, pounding, or irregular heartbeat
  • Very high body temperature; heavy sweating; hot, flushed skin
  • Severe agitation, paranoia, panic, or confusion
  • Severe headache; muscle rigidity or twitching
  • Seizures
  • Signs of stroke — face drooping, one-sided weakness, slurred speech
  • Difficulty breathing; collapse or unconsciousness

What to do

  1. Call emergency services for chest pain, overheating, seizure, or unresponsiveness
  2. Move them to a cool, quiet place and reduce stimulation
  3. Cool the body — remove excess clothing, apply cool damp cloths, fan them
  4. Keep them calm; reassure — panic worsens the cardiovascular strain
  5. If seizing, protect from injury (don't restrain); recovery position afterward
  6. Monitor breathing and be ready to give rescue breaths / CPR

Most stimulant overdoses settle with cooling, a calm environment, and time. The medical danger is hyperthermia, cardiac events (arrhythmia, heart attack, stroke), and seizures — get help immediately if any appear.

988 Suicide & Crisis LifelineFireside Project: 62-FIRESIDE

Version r1 · Not medical advice

References

  1. [1]
    ^Rothman RB, Baumann MH, Dersch CM, Romero DV, Rice KC, Carroll FI, Partilla JS (2001) Amphetamine-type central nervous system stimulants release norepinephrine more potently than they release dopamine and serotonin — Synapse PMID:11071707
  2. [2]
    ^Alexander M, Rothman RB, Baumann MH, et al. (2005) Noradrenergic and dopaminergic effects of (+)-amphetamine-like stimulants in the baboon Papio anubis — Synapse PMID:15729739
  3. [3]
    ^Hendricks EJ, Greenway FL (2011) A study of abrupt phentermine cessation in patients in a weight management program — American Journal of Therapeutics doi:10.1097/mjt.0b013e3181d070d7
  4. [4]
    ^Gate Pharmaceuticals/Teva Pharmaceuticals (2012) Phentermine Hydrochloride Tablets (Adipex-P) Prescribing Information Link
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