Minoxidil (Loniten), a potent antihypertensive medication, exerts robust antihypertensive effects while also posing a risk of a range of potential adverse reactions.

Common and Serious Adverse Reactions of Minoxidil 

1. Common and Predictable Adverse Reactions

(1) Hypertrichosis (≥80%): This is the most prevalent adverse reaction, with approximately 80% of patients experiencing lengthening, thickening, and darkening of body hair. It typically manifests 3–6 weeks after treatment initiation, first appearing on the face (temple, glabella, cheeks) and then spreading to the trunk and extremities. This phenomenon is reversible within 1–6 months of drug discontinuation.

(2) Fluid Retention and Edema (≈7%): Presented as rapid weight gain and swelling of the ankles or face, it is a direct manifestation of drug-induced sodium and water retention.

(3) Electrocardiographic T-wave Abnormalities (≈60%): Most are benign, non-specific changes, usually without clinical symptoms. They may resolve or stabilize with continued treatment and do not indicate myocardial injury.

(4) Nausea/Vomiting: Incidence varies; generally mild in severity.

2. Serious but Uncommon Adverse Reactions

(1) Pericardial Disorders: Including pericarditis and pericardial effusion, which can occasionally progress to cardiac tamponade. The incidence is approximately 3% in non-dialysis patients, with an increased risk particularly in those with renal insufficiency.

(2) Tachycardia and Exacerbation of Angina: Caused by drug-induced reflex increases in heart rate and cardiac output.

(3) Allergic Reactions: A small number of patients develop rashes; severe cutaneous adverse reactions (e.g., toxic epidermal necrolysis, Stevens-Johnson syndrome) are extremely rare.

(4) Hematological Effects: Isolated case reports of thrombocytopenia or leukopenia.

Management and Mitigation Strategies for Side Effects

1. Core Prevention Strategy: Combination Therapy

(1) Counteracting Fluid Retention: Concomitant use of a potent diuretic (typically a loop diuretic such as furosemide) is mandatory, along with strict sodium restriction. Patients should monitor their weight daily; if weight increases by more than 5 pounds (≈2.3 kg) in a short period, they should contact a healthcare provider immediately to adjust the diuretic regimen.

(2) Controlling Heart Rate: Concomitant use of a beta-blocker (e.g., propranolol) or other sympathetic inhibitors (e.g., methyldopa, clonidine) is required to prevent or alleviate reflex tachycardia and angina.

2. Management of Specific Adverse Reactions

(1) Hypertrichosis: Patients must be fully informed before treatment, especially females and children. If it occurs, management options include shaving or depilatories; treatment discontinuation is unnecessary as the condition is reversible upon stopping the drug.

(2) Pericardial Effusion: Patients should be aware of associated symptoms (e.g., chest pain, dyspnea, persistent cough) and seek immediate medical attention for evaluation, including echocardiography, if symptoms arise. Treatment may involve intensified diuresis, pericardiocentesis, or consideration of minoxidil discontinuation.

(3) Severe Allergic or Cutaneous Reactions: Discontinue the drug immediately and seek medical care.

3. Patient Self-Monitoring and Indications for Medical Attention

Patients should undergo regular monitoring and promptly report the following "alarm signals":

(1) Sustained increase in resting heart rate (≥20 beats per minute above baseline).

(2) Rapid weight gain (>5 pounds) in a short period or marked edema.

(3) Dyspnea, particularly exacerbated when lying supine.

(4) New-onset or worsening chest pain and shoulder/back pain.

(5) Severe dizziness or syncope.

Proper Storage of the Medication

1. Storage Temperature

Store at a controlled room temperature of 20°C to 25°C (68°F to 77°F).

2. Storage Conditions

Keep the bottle tightly closed in the original packaging, and protect from light, moisture, and excessive heat (e.g., do not store in the bathroom or near kitchen stovetops).

3. Safe Storage

Store the medication out of the reach of children and pets to prevent accidental ingestion.

4. Disposal of Expired Medication

Do not use expired drugs and dispose of unused/expired medication in accordance with local regulations.