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. 2021 Jul 8;59(8):539–548. doi: 10.5414/CP203943

Table 4. Adverse events reported by patients who received phentermine orally for 6 months.

Adverse event Phentermine Total (n = 932) p-value
15 mg vs. 30 mg
15 mg (n = 400) 30 mg (n = 532)
Cardiac disorders
   Dyspnea 1 (0.3) 3 (0.6) 4 (0.4) 0.6
Ear and labyrinth disorders
   Tinnitus 1 (0.3) 4 (0.8) 5 (0.5) 0.3
Gastrointestinal disorders
   Abdominal pain 2 (0.5) 13 (2.4) 15 (1.6) 0.03
   Constipation 14 (3.5) 22 (4.1) 36 (3.9) 0.7
   Dry mouth 25 (6.3) 74 (13.9) 99 (10.6) < 0.0001
   Dyspepsia 3 (0.8) 8 (1.5) 11 (1.2) 0.4
   Nausea 2 (0.5) 6 (1.1) 8 (0.9) 0.5
   Vomiting 1 (0.3) 4 (0.8) 5 (0.5) 0.4
General disorders and administration site conditions
   Ataxia 2 (0.3) 0 (0) 2 (0.1) 0.5
   Hyperhidrosis 4 (1) 1 (0.2) 5 (0.5) 0.2
   Irritability 2 (0.5) 1 (0.2) 3 (0.3) 0.6
Metabolism and nutrition disorders
   Hyperphagia 8 (2) 15 (2.8) 23 (2.5) 0.5
   Increased appetite 13 (3.3) 44 (8.3) 57 (6.1) 0.002
   Polydipsia 5 (1.3) 20 (3.8) 25 (2.7) 0.02
Musculoskeletal and connective tissue disorders
   Back pain 6 (1.6) 23 (4.4) 29 (3.1) 0.1
   Neck pain 1 (0.3) 4 (0.8) 5 (0.6) 0.3
   Pain in extremity 14 (3.5) 31 (5.8) 45 (4.8) 0.2
Neoplasms benign, malignant, and unspecified
   Acanthosis nigricans 2 (0.5) 22 (4.1) 24 (2.6) < 0.0001
Nervous system disorders
   Headache 8 (2.0) 14 (2.6) 22 (2.4) 0.7
   Dizziness 2 (0.5) 22 (4.1) 24 (2.6) < 0.0001
   Vertigo 1 (0.3) 0 (0) 1 (0.1) 0.4
   Muscle weakness 5 (1.3) 5 (0.9) 10 (1.1) 0.8
Psychiatric disorders
   Anxiety 9 (2.3) 28 (5.3) 37 (4) 0.03
   Depression 4 (1) 7 (1.3) 11 (1.2) 0.8
   Insomnia 8 (2.0) 15 (2.8) 23 (2.5) 0.5
   Nervousness 1 (0.3) 6 (1.1) 7 (0.8) 0.1
   Stress 17 (4.3) 63 (11.8) 80 (8.6) < 0.0001
Respiratory, thoracic, and mediastinal disorders
   Cough 2 (0.5) 4 (0.8) 6 (0.6) 0.8
   Hyposmia 1 (0.3) 0 (0) 1 (0.1) 0.4
   Sputum increased 0 (0) 2 (0.4) 2 (0.2) 0.5
Renal and urinary disorders
   Polyuria 1 (0.3) 0 (0) 1 (0.1) 0.4
   Urinary incontinence 1 (0.3) 0 (0) 1 (0.1) 0.4
   Urinary retention 1 (0.3) 1 (0.3) 2 (0.2) 0.9
   Bladder spasm 1 (0.3) 2 (0.4) 3 (0.3) 0.7
Skin and subcutaneous tissue disorders
   Stretch marks 11 (2.8) 27 (5.1) 38 (4.1) 0.09
Total 179 491 670 0.0001

Data expressed as the number of patients (%). Adverse events were classified according to the Medical Dictionary for Regulatory Activities Terminology. p-values were obtained with χ2.