Topical: Incidence of adverse events is not always reported.
Cardiovascular: Increased left ventricular end-diastolic volume, increased cardiac output, increased left ventricular mass, dizziness, tachycardia, edema, transient chest pain, palpitation, increase or decrease in blood pressure, increase or decrease in pulse rate (1.5%, placebo 1.6%)
Central nervous system: Headache, dizziness, taste alterations, faintness, lightheadedness (3.4%, placebo 3.5%), vertigo (1.2%, placebo 1.2%), anxiety (rare), mental depression (rare), fatigue (rare 0.4%, placebo 1%)
Dermatologic: Local irritation, dryness, erythema, allergic contact dermatitis (7.4%, placebo 5.4%), pruritus, scaling/flaking, eczema, seborrhea, papular rash, folliculitis, local erythema, flushing, exacerbation of hair loss, alopecia, hypertrichosis, increased hair growth outside the area of application (face, beard, eyebrows, ear, arm)
Endocrine & metabolic: Menstrual changes, breast symptoms (0.5%, placebo 0.5%)
Gastrointestinal: Diarrhea, nausea, vomiting (4.3%, placebo 6.6%), weight gain (1.2%, placebo 1.3%)
Genitourinary: Urinary tract infection (rare), renal calculi (rare), urethritis (rare), prostatitis (rare), epididymitis (rare), impotence (rare)
Hematologic:
Lymphadenopathy, thrombocytopenia, anemia (0.3%, placebo 0.6%)
Neuromuscular & skeletal: Fractures, back pain, retrosternal chest pain of muscular origin, tendonitis (2.6%, placebo 2.2%), weakness
Ocular: Conjunctivitis, visual disturbances, decreased visual acuity
Respiratory: Bronchitis, upper respiratory infection, sinusitis (7.2%, placebo 8.6%)
http://www.umm.edu/altmed/drugs/minoxidil-087800.htm