Phentermine side effects: what 6,385 FDA adverse event reports show
Drug class
Sympathomimetic amine anorectic
Label matched
Phentermine Hydrochloride (Phentermine Hydrochloride)
Who reports
6,385 reports · 57% serious · 415 with death outcome · 86% female
Used for
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).
What it is
Phentermine hydrochloride USP has the chemical name of α,α,-Dimethylphenethylamine hydrochloride.
Boxed warning
None in the current label
Causality screen of the 40 strongest signals
What the badges mean
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
- Outcome field, not a reaction Death is a report outcome, not a reaction term. It is dominated by the underlying illness; see the seriousness profile and the boxed warning instead.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 463 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Impaired gastric emptying | 90 | 23.3 19.0–28.7ROR 23.6 · χ² 1,888 / p <1e-300 | 23.1 EB05 19.3 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious PRR 26.5 · 97% consumer | no trial data cached |
| Gallbladder disorder | 69 | 12.7 10.0–16.1ROR 12.8 · χ² 729 / p 6e-161 | 12.5 EB05 10.1 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious PRR 14.1 | no trial data cached |
| Cholecystitis | 40 | 11.1 8.1–15.1ROR 11.1 · χ² 356 / p 1e-79 | 10.6 EB05 8.0 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 11.4 · 72% consumer | no trial data cached |
| Cholelithiasis | 109 | 10.9 9.1–13.2ROR 11.1 · χ² 973 / p 7e-214 | 10.8 EB05 9.1 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious PRR 11.6 | no trial data cached |
| Cholecystectomy | 33 | 9.6 6.8–13.4ROR 9.6 · χ² 244 / p 3e-55 | 8.9 EB05 6.5 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 10.0 | no trial data cached |
| Chronic kidney disease | 204 | 8.8 7.6–10.0ROR 9.0 · χ² 1,395 / p <1e-300 | 8.6 EB05 7.7 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 9.0 | no trial data cached |
| Subarachnoid haemorrhage | 26 | 8.4 5.7–12.3ROR 8.4 · χ² 161 / p 3e-37 | 7.6 EB05 5.3 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 8.5 · 100% clinician | no trial data cached |
| Mitral valve incompetence | 25 | 7.3 4.9–10.7ROR 7.3 · χ² 129 / p 4e-30 | 6.5 EB05 4.6 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 6.5 | no trial data cached |
| Injury | 155 | 7.2 6.2–8.4ROR 7.4 · χ² 824 / p 1e-181 | 7.1 EB05 6.2 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 9.1 | no trial data cached |
| Obesity | 35 | 7.2 5.2–10.0ROR 7.2 · χ² 181 / p 2e-41 | 6.7 EB05 5.0 · IC025 +2.2 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 7.0 | no trial data cached |
| Sleep apnoea syndrome | 40 | 6.9 5.0–9.4ROR 6.9 · χ² 195 / p 1e-44 | 6.4 EB05 4.9 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 7.9 | no trial data cached |
| Serotonin syndrome | 40 | 6.9 5.0–9.4ROR 6.9 · χ² 195 / p 1e-44 | 6.4 EB05 4.9 · IC025 +2.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 7.0 | no trial data cached |
| End stage renal disease | 38 | 6.8 4.9–9.3ROR 6.8 · χ² 181 / p 1e-41 | 6.3 EB05 4.8 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 6.9 | no trial data cached |
| Deep vein thrombosis (leg blood clot) | 128 | 6.4 5.4–7.7ROR 6.6 · χ² 584 / p 3e-129 | 6.3 EB05 5.4 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 6.7 | no trial data cached |
| Dysmenorrhoea | 25 | 6.3 4.2–9.3ROR 6.3 · χ² 106 / p 4e-25 | 5.7 EB05 4.0 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Paranoia | 32 | 6.1 4.3–8.6ROR 6.1 · χ² 130 / p 2e-30 | 5.6 EB05 4.2 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 6.8 | no trial data cached |
| Economic problem | 26 | 5.5 3.8–8.1ROR 5.6 · χ² 92 / p 4e-22 | 5.1 EB05 3.6 · IC025 +1.7 3/3 methods agree | Reporting / coding artifact | serious PRR 6.1 | no trial data cached |
| Hyperlipidaemia | 20 | 5.5 3.5–8.5ROR 5.5 · χ² 69 / p 5e-17 | 4.9 EB05 3.4 · IC025 +1.6 3/3 methods agree | Likely indication confounding term in indications | serious PRR 5.8 | no trial data cached |
| Anhedonia | 44 | 5.5 4.1–7.3ROR 5.5 · χ² 156 / p 5e-36 | 5.2 EB05 4.0 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 6.0 | no trial data cached |
| Feeling jittery | 31 | 5.3 3.8–7.6ROR 5.4 · χ² 105 / p 7e-25 | 5.0 EB05 3.7 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious n=14 | no trial data cached |
| Impaired quality of life | 23 | 5.3 3.5–7.9ROR 5.3 · χ² 75 / p 2e-18 | 4.8 EB05 3.4 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 4.1 | no trial data cached |
| Supraventricular tachycardia | 15 | 5.2 3.1–8.5ROR 5.2 · χ² 46 / p 6e-12 | 4.5 EB05 2.9 · IC025 +1.3 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 | no trial data cached |
| Sleep disorder due to a general medical condition | 25 | 5.1 3.4–7.5ROR 5.1 · χ² 78 / p 6e-19 | 4.7 EB05 3.3 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | 92% clinician | no trial data cached |
| Acute hepatic failure | 21 | 5.1 3.3–7.8ROR 5.1 · χ² 65 / p 5e-16 | 4.6 EB05 3.2 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 5.2 | no trial data cached |
| Increased appetite | 29 | 5.1 3.5–7.3ROR 5.1 · χ² 91 / p 8e-22 | 4.7 EB05 3.4 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 4.1 · 82% consumer | no trial data cached |
| Pelvic pain | 28 | 5.1 3.5–7.3ROR 5.1 · χ² 87 / p 5e-21 | 4.7 EB05 3.4 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 6.2 | no trial data cached |
| Ventricular fibrillation | 17 | 5.0 3.1–8.1ROR 5.0 · χ² 51 / p 5e-13 | 4.5 EB05 3.0 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 | no trial data cached |
| Cardiomyopathy | 22 | 4.9 3.2–7.4ROR 4.9 · χ² 64 / p 6e-16 | 4.5 EB05 3.1 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 5.0 · 100% clinician | no trial data cached |
| Sinus tachycardia | 21 | 4.9 3.2–7.5ROR 4.9 · χ² 61 / p 3e-15 | 4.4 EB05 3.1 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 5.0 | no trial data cached |
| Pulmonary embolism (lung blood clot) | 137 | 4.7 4.0–5.6ROR 4.8 · χ² 399 / p 5e-89 | 4.6 EB05 4.0 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 4.8 | no trial data cached |
| Embedded device | 14 | 4.7 2.8–7.9ROR 4.7 · χ² 37 / p 7e-10 | 4.1 EB05 2.6 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 | no trial data cached |
| Insurance issue | 21 | 4.6 3.0–7.1ROR 4.7 · χ² 56 / p 3e-14 | 4.2 EB05 2.9 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 7.4 | no trial data cached |
| Respiratory arrest | 38 | 4.5 3.3–6.2ROR 4.5 · χ² 100 / p 9e-24 | 4.3 EB05 3.3 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 4.6 · ♀ 64% (drug 86%) · 91% clinician | no trial data cached |
| Hunger | 18 | 4.4 2.8–7.0ROR 4.4 · χ² 44 / p 2e-11 | 4.0 EB05 2.7 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious n=4 | no trial data cached |
| Vitamin d deficiency | 13 | 4.4 2.5–7.5ROR 4.4 · χ² 31 / p 2e-8 | 3.8 EB05 2.4 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 5.4 | no trial data cached |
| Rotator cuff syndrome | 17 | 4.3 2.7–7.0ROR 4.3 · χ² 40 / p 1e-10 | 3.9 EB05 2.6 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial data cached |
| Vaginal discharge | 13 | 4.3 2.5–7.3ROR 4.3 · χ² 29 / p 3e-8 | 3.8 EB05 2.4 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious n=5 | no trial data cached |
| Bipolar disorder | 14 | 4.2 2.5–7.1ROR 4.2 · χ² 31 / p 1e-8 | 3.7 EB05 2.4 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 4.9 | no trial data cached |
| Completed suicide (death by suicide) | 107 | 4.2 3.5–5.0ROR 4.2 · χ² 256 / p 6e-58 | 4.1 EB05 3.5 · IC025 +1.7 3/3 methods agree | Outcome field, not a reaction | serious PRR 4.2 · 92% clinician | no trial data cached |
| Poisoning | 16 | 4.2 2.6–6.8ROR 4.2 · χ² 35 / p 1e-9 | 3.8 EB05 2.5 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 4.0 | no trial data cached |
Trial evidence (ClinicalTrials.gov)
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Drug ineffective (drug did not work) | 558 | 1.4 1.3–1.5ROR 1.4 · χ² 65 / p 4e-16 | 1.4 EB05 1.3 · IC025 +0.3 | Reporting / coding artifact | serious PRR 1.0 | no trial data cached |
| Nausea | 517 | 2.2 2.0–2.3ROR 2.3 · χ² 330 / p 5e-74 | 2.1 EB05 2.0 · IC025 +1.0 | Not in label — unassessed | serious PRR 2.5 | no trial data cached |
| Pain | 475 | 2.5 2.3–2.8ROR 2.7 · χ² 453 / p 8e-101 | 2.5 EB05 2.3 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious PRR 2.9 | no trial data cached |
| Headache | 341 | 1.8 1.6–2.0ROR 1.8 · χ² 121 / p 2e-28 | 1.8 EB05 1.6 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 2.0 | no trial data cached |
| Anxiety | 325 | 3.7 3.4–4.2ROR 3.9 · χ² 659 / p 1e-145 | 3.7 EB05 3.4 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 4.4 | no trial data cached |
| Vomiting | 265 | 1.9 1.6–2.1ROR 1.9 · χ² 106 / p 4e-25 | 1.9 EB05 1.7 · IC025 +0.7 | Not in label — unassessed | serious PRR 2.0 | no trial data cached |
| Dizziness | 232 | 1.5 1.3–1.7ROR 1.5 · χ² 43 / p 3e-11 | 1.5 EB05 1.4 · IC025 +0.4 | Labeled adverse reaction exact term | serious PRR 1.5 | no trial data cached |
| Weight increased (weight gain) | 214 | 3.2 2.8–3.6ROR 3.2 · χ² 316 / p 6e-71 | 3.1 EB05 2.8 · IC025 +1.4 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 3.2 | no trial data cached |
| Chronic kidney disease | 204 | 8.8 7.6–10.0ROR 9.0 · χ² 1,395 / p <1e-300 | 8.6 EB05 7.7 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 9.0 | no trial data cached |
| Depression | 199 | 2.9 2.5–3.3ROR 2.9 · χ² 241 / p 1e-54 | 2.8 EB05 2.5 · IC025 +1.3 3/3 methods agree | Not in label — unassessed | serious PRR 3.3 | no trial data cached |
| Arthralgia (joint pain) | 187 | 1.5 1.3–1.7ROR 1.5 · χ² 29 / p 3e-8 | 1.5 EB05 1.3 · IC025 +0.3 | Not in label — unassessed | serious PRR 1.5 | no trial data cached |
| Constipation | 179 | 2.7 2.4–3.1ROR 2.8 · χ² 194 / p 2e-44 | 2.7 EB05 2.4 · IC025 +1.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.4 · 72% consumer | no trial data cached |
| Abdominal pain | 178 | 2.5 2.2–2.9ROR 2.6 · χ² 163 / p 2e-37 | 2.5 EB05 2.2 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 2.8 | no trial data cached |
| Insomnia (trouble sleeping) | 167 | 2.1 1.8–2.4ROR 2.1 · χ² 91 / p 9e-22 | 2.0 EB05 1.8 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 1.9 | no trial data cached |
| Acute kidney injury (sudden kidney damage) | 162 | 3.5 3.0–4.1ROR 3.6 · χ² 288 / p 8e-65 | 3.5 EB05 3.0 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 3.6 | no trial data cached |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Impaired gastric emptying — n=90, PRR 23.3
- Gallbladder disorder — n=69, PRR 12.7
- Cholecystitis — n=40, PRR 11.1
- Cholelithiasis — n=109, PRR 10.9
- Cholecystectomy — n=33, PRR 9.6
- Chronic kidney disease — n=204, PRR 8.8
- Subarachnoid haemorrhage — n=26, PRR 8.4
- Mitral valve incompetence — n=25, PRR 7.3
- Injury — n=155, PRR 7.2
- Sleep apnoea syndrome — n=40, PRR 6.9
✓ A hand-written Bradford Hill causality assessment exists for this drug: Phentermine ↔ Tachycardia.
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Phentermine?
In FDA FAERS, the most frequently co-reported reaction terms for Phentermine are nausea, pain, headache, anxiety, vomiting, dizziness. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Phentermine have an FDA boxed warning?
No. The FDA label retrieved for Phentermine has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Phentermine causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID 02b8f684-b1ca-4ab7-9567-bcacc6a92779, effective 20250714; matched on
openfda.generic_name.exact:"PHENTERMINE HYDROCHLORIDE") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 503 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath
Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.