Antihypertensive drugs

ANTIHYPERTENSIVE DRUGS

>140mm/90mm => hypertension

These are drugs used to lower BP in hypertension.
Factors determine BP:

1) Total blood circulation

2) Cardiac output

3) Peripheral vessel resistance

Classification:

1) Antiadrenergic:

a) Central action drugs:

- Clonidine

- Methyldopa

b) Peripheral action drugs:

- Propranolol, Atenolol => see the topic adrenoblockers

- Reserpine => sympatholytic
2) Vasodilators:

-Papaverine hydrochloridim; Hydralazin

- Dibazol; Nitroprusside Na+

- Magnesium sulfate

3) Ca+2 channel blockers:

- Verapamil

- Nifedipin

- Amlodipin

4) ACE inhibitors:

- Enalapril; Perindopril

- Captopril; Ramipril

- Lisinopril; Fosinopril

5) AT blockers:

- Losartan; Irbesartan

- Condesartan

- Valsartan

6) Diuretics see the topic

Clonidin: easily passes through BBB, stimulates α2-adrenoreceptors located on membranes of inhibitory neurons in vasomotor centers, i.e reduces sympathetic innervation at the central level => antihypertensive effect.

Increases tonus of parasympathetic neurons => decreases cardiac output.

Has a sedative effect (side effect).

Inhibits secretion of noradrenaline => decreases peripheral vascular resistance.

It well absorbed through GIT.

Peak after 1 hour, effect till 15 hours.

i.m. – after 15 min old drug 1960’s.

i.v. – after 4 min only with prescription.

Methyldopa:

Easily penetrate through BBB, decreases total peripheral resistance (t.p.r) and secretion of noradrenaline, decreases preload.

Kinetics: max effect after 5 h, till 2 days.

Uses: treat hypertension during pregnancy.

Adrenoblockers:

- Prazosin being used rarely, as causes fluid retention and increases the risk for CHF.

- β-blockers = mild antihypertensives.

Contraindications: cardiac, pulmonary and peripheral vascular diseases.

- α+ β-blocker Labetalol reduces t.p.r and acts faster than pure β-blockers.

Uses: i.v. for rapid BP reduction in hyperadren. states, clonidine withdrawal, eclampsia.

- Carvedilol is β + weak α, blocker produces vasodilatation. It is used to treat CHF, hypertension.
Vasodilators:

• 
  Apressine (Hydralazine) is used as a second line alternative only in combination with a diuretic and/or β-blocker for patients not achieving target BP with first line drugs.
  

It is one of preferred antihypertensives during pregnancy, especially preeclampsia.

• 
  Sodium nitroprusside
  

It uses only at hospital.

It is rapidly (within seconds) and acting vasodilator, has brief duration of

action (2-5 min). It relaxes both resistance and capacitance vessels.

It is popular in the hypertensive emergency,

(50 mg + 500 ml glucose => i.v. infusion).

• 
  Magnesium sulfate (MgSO4) sol. 25% - 10ml
  

Effects are:

- Antihypertensive

- Sedative

- Anticonvulsant

Uses: - to arrest hypertonic srtoke

- to treat eclampsia

- infused i.v. it is a first line drug for prevention and treatment of seizures in preeclampsia and eclampsia. It is tocolytic by competing with Ca+2 ions.
Papaverine hydrochloride 2% - 2 ml, tab. 40 mg => spasmolytic.

Dibazol 1% - 1 ml => old drugs for crisis relief.
Ca+2 channel blockers:

- Verapamil

- Nifedipine

- Amlodipine

They are first line antihypertensive drugs, preferred in the elderly hypertensive.
ACE (angiotensin converting enzyme) inhibitors

They are one of the first choice drugs.

They are the most appropriate antihypertensives in patients with diabetes, nephropathy, left ventricular hypertrophy, CHF, angina and post MI.
Side effects: dry cough due to bradykinin secretion.

- Enalapril 5 mg tab.

- Lisinopril 5 mg

- Monopril 10 mg

- Ramipril

- Perindopril

- Fosinopril

- Captopril