Although anagrelide has no absolute contraindications, special populations and concomitant medications require extra caution, and adverse reactions involve multiple systems.

I. Contraindications and Situations to Avoid

1. No Absolute Contraindications

The prescribing information clearly lists "none" for absolute contraindications. However, this does not mean it can be used by everyone. The following situations belong to "avoid use" or "use with caution after weighing benefits and risks."

2. Contraindications Related to QT Interval Prolongation

Use should be avoided in those with known risk of QT interval prolongation, including congenital long QT syndrome, a history of acquired QTc prolongation, and hypokalemia. Concomitant use should also be avoided in patients taking drugs that can prolong the QT interval (such as chloroquine, clarithromycin, fluconazole, amiodarone, sotalol, etc.).

3. Severe Hepatic Impairment

Use should be avoided in patients with severe hepatic impairment. Patients with moderate hepatic impairment require dose reduction and close monitoring, while those with mild impairment need an assessment of risks and benefits before treatment.

4. Concomitant Use with PDE3 Inhibitors

Anagrelide itself is a PDE3 inhibitor, and concomitant use with other PDE3 inhibitors (such as cilostazol and milrinone) should be avoided to prevent worsening of inotropic effects and cardiovascular toxicity.

II. Cardiovascular and Bleeding Risks Requiring Key Monitoring

1. Cardiovascular Toxicity

Anagrelide can cause QT interval prolongation, torsades de pointes, and ventricular tachycardia. All patients should undergo an ECG before treatment and be monitored for cardiovascular reactions during treatment. Patients with heart failure, bradycardia, or electrolyte disturbances need periodic ECG rechecks. PDE3 inhibition can also lead to vasodilation, tachycardia, palpitations, and even congestive heart failure.

2. Pulmonary Hypertension

Pulmonary hypertension has been reported during use. Underlying cardiopulmonary disease should be assessed before treatment, and attention should be paid during treatment to manifestations such as difficulty breathing, lower limb edema, and bluish lips.

3. Bleeding Risk

Concomitant use of anagrelide and aspirin significantly increases major bleeding events. Bleeding risk is also increased when used with anticoagulants, antiplatelet drugs, nonsteroidal anti-inflammatory drugs, and selective serotonin reuptake inhibitors. Monitor for vomiting blood, black stools, abnormal bruising, etc.

4. Pulmonary Toxicity

Interstitial lung disease (including allergic alveolitis, eosinophilic pneumonia, and interstitial pneumonitis) is associated with use, mostly presenting as progressive difficulty breathing and pulmonary infiltrates. If suspected, discontinue the drug and evaluate; symptoms may improve after discontinuation.

III. Common Adverse Reactions in Other Systems

1. Neurological and Systemic Reactions

Headache is the most common, and dizziness, paresthesia, fatigue, fever, pain, peripheral edema, and malaise may also occur. These reactions are mostly dose-related and can be reduced after dose adjustment.

2. Digestive System Reactions

Diarrhea, nausea, abdominal pain, vomiting, bloating, decreased appetite, and indigestion are relatively common. Taking the drug with meals is recommended to reduce gastrointestinal irritation.

3. Other Cardiac and Respiratory Reactions

Palpitations, tachycardia, chest pain, arrhythmia, angina pectoris, syncope, and heart failure have all been reported. Difficulty breathing and cough may also occur.

4. Skin and Blood System

Rash, itching, and hair loss may be seen. Anemia, thrombocytopenia, ecchymosis, and bleeding tendency need to be monitored through blood routine tests.

5. Other Less Common Reactions

These include elevated liver enzymes, depression, insomnia, abnormal vision, tinnitus, hematuria, and renal impairment. Pediatric patients may also experience fever, epistaxis, headache, and fatigue.