히드랄라진

혈관 확장제

히드랄라진(Hydralazine)은 강력한 **직접 작용 세동맥 확장제**로, 주로 전신 고혈압 관리 및 소동물의 울혈성 심부전(CHF) 보조 치료 시 **후부하 감소제**로 사용됩니다. * **임상적 유용성**: 승모판 폐쇄 부전증, 큰 심실 중격 결손 또는 중증 대동맥판 역류증 환자에서 심장이 혈액을 펌프질할 때 받는 저항(후부하)을 줄이는 것이 중요하므로 특히 유익합니다. * **난치성 심부전**: 승모판 폐쇄 부전증이 있는 개에서 ACE 억제제(예: 에날라프릴)만으로 임상적 개선이 불충분할 때 자주 사용됩니다. * **병용 요법**: 나트륨 및 수분 저류를 유발하는 경향을 상쇄하기 위해 이뇨제와 자주 병용되며, 반사성 빈맥을 완화하기 위해 베타 차단제와 병용하기도 합니다. * **한계점**: 유의미한 판막 역류 없이 원발성 심근 질환(예: 확장성 심근병증)만이 문제인 경우 심부전 치료에 큰 도움이 되지 않습니다.

작용 기전: Hydralazine acts as a **semicarbazide-sensitive amine oxidase (SSAO) inhibitor**, directly relaxing vascular smooth muscle. * **Mechanism**: Alters cellular calcium metabolism in smooth muscle → interferes with calcium movements → prevents the initiation and maintenance of the contractile state. * **Vascular Selectivity**: Exerts a much greater effect on **arterioles** than on veins. This selective arterial dilation significantly decreases systemic vascular resistance (SVR) and blood pressure. * **Cardiac Effects**: In CHF patients, the reduction in afterload → significantly increases forward cardiac output. * **Compensatory Responses**: In non-CHF hypertensive patients, the sudden drop in blood pressure can trigger baroreceptor-mediated **reflex tachycardia** and activation of the **renin-angiotensin-aldosterone system (RAAS)** → leading to sodium and water retention.

동물 종별 용량

Cats

Adjunctive therapy in treatment of heart failure · start titration at 2.5 mg (total dose) and if necessary, increase up to 10 mg · PO · q12h · Follow similar titration protocols as dogs.
Treatment of systemic hypertension (Fourth step drug) · 0.5 mg/kg · PO · twice daily · Added if systolic BP > 160 mmHg after amlodipine, ACE inhibitor, and spironolactone.
Systemic hypertension · 2.5-10 mg/cat · PO · q12h · Long-term · Start at low dose and titrate upwards cautiously. Monitor blood pressure regularly.

Horses

Adjunctive therapy in treatment of heart failure (afterload reducer) · 0.5 mg/kg · IV · Once · ARCI UCGFS Class 3 Drug.
Adjunctive therapy in treatment of heart failure (long-term therapy) · 0.5-1.5 mg/kg · PO · q12h · Long-term

Dogs

Adjunctive therapy in treatment of heart failure (not receiving ACE inhibitors) · 1 mg/kg (starting dose, titrate up to 3 mg/kg if needed) · PO · q12h · Effective dose is 0.5-3 mg/kg PO q12h. Titrate upwards carefully. If BP monitored, can titrate more rapidly in 1-2 hour intervals.
Acute, fulminant heart failure due to severe mitral regurgitation (not receiving ACE inhibitors) · 2 mg/kg · PO · Once · Given along with IV furosemide. May cause hypotension, but benefits outweigh risks.
Adjunctive therapy in treatment of heart failure (receiving ACE inhibitors) · 0.5 mg/kg (starting dose, increase in 0.5 mg/kg increments to max 3 mg/kg) · PO · q12h · Give with extreme caution as severe hypotension may occur. Blood pressure monitoring required.

투여 경로

POIV

금기

Known hypersensitivity to hydralazine
Coronary artery disease
Hypovolemia
Preexisting hypotension
Hypovolaemia
Hypotension
Renal impairment
Cerebral bleeding

이상반응

Hypotension
Weakness and lethargy
Syncope (fainting)
Reflex tachycardia
Sodium and water retention
GI distress (vomiting, diarrhea)
Increased creatinine levels
SLE-like syndrome (documented in humans, theoretical in animals)
Lacrimation and conjunctivitis
Peripheral neuritis
Blood dyscrasias
Urinary retention
Constipation
Severe hypotension
Anorexia (especially in cats)
Vomiting (especially in cats)

약물 상호작용

ACE-INHIBITORS · May cause additive hypotensive effect; usually used for therapeutic advantage
BETA-BLOCKERS · May cause additive hypotensive effect; usually used for therapeutic advantage
DIAZOXIDE · Potentially could cause profound hypotension
DIURETICS · May cause additive hypotensive effect; usually used for therapeutic advantage · moderate
FUROSEMIDE · Hydralazine may increase furosemide's renal effects
MAO INHIBITORS · May cause additive hypotensive effect
SYMPATHOMIMETICS (e.g., epinephrine) · Hydralazine may cause decreased pressor effect and may cause additive tachycardia
ACE inhibitors (e.g., enalapril, benazepril) · Enhanced hypotensive effects · major
Anaesthetics · Enhanced hypotensive effects · moderate
Beta-blockers (e.g., propranolol) · Enhanced hypotensive effects · moderate
Calcium-channel blockers (e.g., diltiazem, verapamil) · Enhanced hypotensive effects · moderate
Corticosteroids · Enhanced hypotensive effects · minor
NSAIDs · Enhanced hypotensive effects · moderate

모니터링

Baseline thoracic radiographs
Mucous membrane color and capillary refill time
Serum electrolytes and creatinine
Arterial blood pressure (Target MAP 60-80 mmHg for short-term CHF treatment)
Venous PO2
Occasional CBC (due to possibility of blood dyscrasias)
Systemic blood pressure (frequent monitoring during initiation)
Heart rate and rhythm
Renal function (BUN, Creatinine)
Hydration status and body weight (to monitor for fluid retention)

과용량

**Clinical Signs**: Overdoses are characterized by severe hypotension, reflex tachycardia or other arrhythmias, skin flushing, and myocardial ischemia. **Treatment**: * **Decontamination**: Evacuate gastric contents and administer activated charcoal using standard precautions if ingestion was recent and cardiovascular status is stable. * **Cardiovascular Support**: Treat shock using volume expanders. Avoid pressor agents if possible. * **Pressor Agents**: If required to maintain blood pressure, use a minimally arrhythmogenic agent (e.g., phenylephrine or methoxamine). * **Additional Support**: Digitalis agents may be required. Diligently monitor blood pressure and renal function.

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