Hydralazine Pharmacology


About Hydralazine
A direct-acting smooth muscle relaxant, Pyridazine derivative, Antihypertensive(Vasodilator).
Mechanism of Action of Hydralazine
Hydralazine exerts its pharmacological actions by direct vasodilator action on arteriolar smooth muscles with little actions on venous capacitance vessels. It produces after load reduction by dilating resistance vessels which leads to decreasing aortic impedence.So that more blood is pumped even in weaker ventricular contractions. It decreases total peripheral resistance and there is greater decrease in diastolic pressure than systolic pressure. There is a decrease in intracellular Ca2+concentration but there is no reduction in renal blood flow.
Pharmacokinets of Hydralazine
Absorption: It is well absorbed orally, but bioavailability is low in fast acetylators.Distribution: Widely distributed in a highly plasma protein bound form.Metabolism: It is metabolized in liver,plasma and gastrointestinal mucosa. Excretion: Excreted mainly through urine and the rest of dose is excreted through bile and faeces.
Onset of Action for Hydralazine
10 to 30 minutes
Duration of Action for Hydralazine
Up to 6 hours
Half Life of Hydralazine
1 hour
Side Effects of Hydralazine
1. Tachycardia
2. Tachyphylaxis
3. Edema
4. Palpitation
5. Dizziness
6. Dryness of mouth
7. Nasal congestion
8. Headache
9. Palpitation
10. Weakness
11. Orthostatic hypotension
12. Angina
13. Anxiety
14. Sleep disturbances
15. Reversible lupus erythmatosis
16. Paraeshesia
17. Tremor
18. Muscle cramps

Contra-indications of Hydralazine
1. Hypersensitivity to the drug,
2. Ischaemic heart disease
3. Coronary artery diseases
4. Valvular stenosis
5. Pericarditis
6. Aortic aneurism

Special Precautions while taking Hydralazine
1. Renal impairment
2. Hepatic impairment
3. Cardiovascular disorders
4. Cerebro vascular disorders
5. Use with caution along with other antihypertensive drugs
6. Slowly withdraw the drug with caution

Pregnancy Related Information
Use with caution
Old Age Related Information
Breast Feeding Related Information
Children Related Information
Use with caution
Indications for Hydralazine
1. Hypertension
2. Congestive heart failure
3. Pregnancy associated hypertensive crisis
4. Hypertension associated with renal involvement

Interactions for Hydralazine
MAOIs, Thiazide diuretics & TCAs: Antihypertensive effect of hydralazine enhanced.
Sympathomimetics: Use these agents with great caution since hydralazine alone may cause tachycardia and angina.
Propranolol, Metoprolol: Oral bioavailability of these agents may be increased. Also they counteract reflex tachycardia.
Parenteral antihypertensive drugs: (e.g. Diazoxide): Profound hypotensive episodes may occur.
Alcohol: Hydralazine potentiates effect of alcohol.
Typical Dosage for Hydralazine
Oral: Starts with 10mg 6th hourly. Increase the dosage up to 25mg 12th hourly to 6th hourly or 50mg 12th hourly to 6th hourly depending up on the patient`s response.
Maximum daily dose: 200mg
Maximum dose in fast acetylators: 300 to 400mg/day
I.V.: 10 to 20mg. Repeat if required by the patient
Children: Starts with 0.75mg/day. Increased up to 7.5mg/kg/day based on patient`s response.
Heart failure: Starts with 50 to 75mg. Increase the dosage up to 200 to 600mg/day in 2 to 4 divided doses based on patient`s response.
Maximum dose: 3gm/day
Pregnancy associated hypertensive crisis: Starts with 5mg I.V. Increases to 10mg at every half an hour until desired response is obtained.

Schedule of Hydralazine
Storage Requirements for Hydralazine
Store at controlled room temperature at a temperature range of 15 to 30 degree C in a light resistant tightly closed container.
Effects of Missed Dosage of Hydralazine
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose.Continue the regular schedule.Do not double the dose.
Effects of Overdose of Hydralazine
Treatment is supportive and symptomatic. After ingestion empty the stomach by induced emesis and gastric lavage. Administer activated charcoal to reduce absorption.

Home Delivery for Hydralazine in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including hydralazine.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for hydralazine and other medicines and health products. Home delivery services for hydralazine may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take hydralazine only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for hydralazine before they complete the sale. You can get this information while placing the order for hydralazine with the pharmacy.

Hydralazine is a generic medicine name and there are several brands available for it. Some of the brands for hydralazine might be better known than hydralazine itself. If the pharmacy that's willing to deliver medicines to your home doesn't have hydralazine in stock, you can ask for one of the branded alternatives for hydralazine.