====== Hydralazine ======

**Class:** Direct-acting vasodilator  
**Route of administration:** Oral, Intravenous  
**Main indications:**  
  * Hypertension (especially in pregnancy-related hypertensive emergencies)  
  * Congestive heart failure (often combined with nitrates)  

===== Mechanism of Action =====  
Hydralazine causes direct **relaxation of arteriolar smooth muscle**, leading to **arteriolar vasodilation** (with minimal venous effect). This reduces peripheral vascular resistance and lowers systemic blood pressure.

===== Dosage =====  
**Oral:**  
  * Initial: 25 mg two to four times daily  
  * Maintenance: 100–200 mg/day in divided doses

**Intravenous (emergency use):**  
  * Typically 10–20 mg IV every 4–6 hours as needed

===== Adverse Effects =====  
  * Reflex tachycardia  
  * Fluid retention and edema  
  * Drug-induced lupus-like syndrome (especially with doses >200 mg/day)  
  * Headache, flushing, nausea  
  * Postural hypotension

===== Contraindications =====  
  * Coronary artery disease (active ischemia)  
  * Aortic dissection  
  * Hypersensitivity to hydralazine

===== Monitoring =====  
  * Blood pressure and heart rate  
  * Renal function and electrolytes  
  * Antinuclear antibodies (ANA) in long-term therapy to monitor for lupus

===== Notes =====  
  * Often combined with beta-blockers and diuretics to counteract reflex tachycardia and fluid retention  
  * Considered safe during pregnancy