TOPIC OF PRESENTATION:

“VASODILATORS”

PRESENTED BY: HAFSA MARYAM

ROLL NO. 11

DIRECT-ACTING VASODILATORS

FENOLDOPAM

PARENTRAL

HYDRALAZINE

ORAL

MINOXIDIL

ORALSODIUM

NITROPRUSSIDE

PARENTRAL

DIAZOXIDE

PARENTRAL

• Increased sympathetic system outflow.

• This leads to:a. Increased

heart rateb. Increased

cardiac contractility

c. Decreased venous capacitance

• Increased cardiac output.

• VASODILATOR DRUGS

• Decreased systemic vascular resistance.

• Decreased arterial pressure.

• Increased renin release.

• Increased angiotensin II.

Decreased renal sodium

excretion.

Sodium retention, increased

plasma volume

Increased systemic vascular

resistance.

Increased arterial pressure

Increased aldosteron

e

The direct-acting vasodilator

used clinically is Hydralazine (Apresoline)

HYDRALAZINE

` Oral vasodilator but can be

given I/V. Well absorbed. Rapidly metabolized by the liver

during first pass so bioavailability is

o low averaging 25%o variable among individuals. It is also metabolized in part by

acetylation.

40 mg/d to 200 mg/d.

PHARMACOKINETICS OF HYDRALAZINE

Risk of toxicity is increased in slow acetylators.

Rapid acetylators require higher doses.

PHARMACODYNAMICS OF HYDRALAZINE

Opens k+ channels and relaxes the smooth muscles of arterioles.

This leads to decrease in peripheral vascular resistances.

Decrease in arterial blood pressure.

• It causes reflex stimulation of sympathetic system. This leads to increased heart rate Increased myocardial contractility Increased cardiac output Increased plasma renin activity Increased fluid retention.

• This leads to increased arterial pressure and thus antagonizes its antihypertensive action.

• It is thus given with A Beta blocker A diuretic.

• Moderate to severe hypertension• Hypertensive emergency• Heart failure.• Hydralazine monotherapy is used in treatment

of pregnancy induced hypertension.

o Ischemic heart diseaseo Lupus erythematosus

INDICATIONS OF HYDRALAZINE:

CONTRA-INDICATIONS OF HYDRALAZINE:

ADVERSE EFFECTS OF HYDRALAZINE

• CNS:HeadacheDizzinessPeripheral

neuropathy• CVS:

PalpitationFlushingReflex tachycardiaAnginaIschemic

arrhythmias

• GIT:AnorexiaNausea.

• SKIN:SweatingLupus erythematosus

like syndrome characterized by:

• Arthralgia• Myalgia• Skin rashes• fever

It is prodrug. Administered orally but

can be applied topically. 90% absorption from

gastrointestinal tract. Topical minoxidil is

poorly absorbed averaging 2%.

It is widely distributed in body tissues.

Plasma half life is 4 hrs.

Metabolized in the liver by the process of conjugation forming its sulfates.

Action is due to its active metabolite minoxidil sulphate.

It is excreted mainly by the kidneys.

5-40mg/d in single or divided doses.

Due to reflex tachycardia it is given along with a diuretic and Beta blocker.

1. Opens k+ channels in smooth muscles of arterioles.

2. Hyperpolarization of smooth muscles leading to dilation of blood vessels.

3. Decrease in peripheral vascular resistance.

4. Decrease in blood pressure.

IT CAUSES VASODILATONBY THE FOLLOWING MECHANISM:

Severe hypertensionSevere hypertension

coupled with renal function impairment.

Topical use for correction of baldness in males

CNS:Headache.

CVS:TachycardiaPalpitationAnginaPericardial effusion.

SKIN: Sweating Flushing.

ENDO:Hirsuitism

(hypertrichosis) in females.

RENAL:Edema.

It is an effective and relatively long-acting parentral vasodilator.

It has thiazide diuretic like action but no diuretic effects.

It is a parentral direct acting vasodilator.

It is administered parentrally.

It is bound extensively to serum albumin.

Its is both metabolized and excreted unchanged.

Its metabolic pathways are not well characterized.

Its half life is about 24 hours

The blood pressure lowering effect of diazoxide is established within 5 min and lasts for 4-12 hours.

Treatment should be started with low doses about 50 to 150mg.

Dose of 150 mg should be increased after every 5 min until BP is lowered.

1. It causes vasodilation by: Opening k+ channels in the smooth

muscles of arterioles thus relaxing them.

This decreases peripheral vascular resistance.

Decreased arterial blood pressure.

Reflex sympathetic system stimulation.

2. It also relaxes smooth muscles other than the vascular ones.

3. It inhibits the release of insulin from beta cells of pancreas thus leading to hyperglycemia.

I/V in hypertensive emergencies.Orally in hypoglycemia caused by

hyperinsulinemia.

Diabetes mellitusCongestive cardiac failure.

CVS:Severe hypotension resulting in stroke or myocardial infarction.AnginaCardiac failure in pts with ischemic heart disease.

ENDO:Hyperglycemia

RENAL:edema

It is administered parentrally by continuous I/V infusion.

It is poisonous if given orally because of hydrolysis into cyanide.

It is taken up and metabolized by RBCs with liberation of cyanide.

Mitochondrial enzyme rhodanase in the presence of a sulfur donor metabolizes it to less toxic thiocyanate.

Thiocyanate is distributed in ECF and eliminated by the kidneys.

Dosage typically begins at 0.5ug/kg/min.

It may be increased up to 10ug/kg/min as necessary to control blood pressure.

It dilates both arterial and venous vessels.

Its action is due to nitric oxide.

Nitric oxide of sodium nitroprusside.

Activation of guanylyl cyclase (GC) in smooth muscles of blood vessels.

Increased intracellular cGMP.

Relaxation of vascular smooth muscle.

CVS: Directly relaxes both

arterial and venous smooth muscles equally

Decreases BP in supine and upright position.

Decreases myocardial oxygen demand due to increased venous capacitance.

Slight increase in heart rate and decrease in cardiac output except in cardiac failure.

In cardiac failure it may decrease heart rate and increase cardiac output.

RENAL: Renal blood flow is

maintained and renin secretion is increased.

Hypertensive crisisHeart failureCardiac surgery to produce hypotensionCardiogenic shockAortic dissectionRegurgitant valvular disease.

Cyanide toxicity:Metabolic acidosisExcessive

hypotensionArrhythmiasdeath

BLOOD:Methemoglobinemia

THIOCYANATE POISONING: Weakness Disorientation Psychosis Muscle spasms Convulsions.

ENDO: Delayed hypothyroidism

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