182 Section 4/ Drugs Acting on Cardiovascular & Urinary SystemGIT and undergoes metabolism in liver to
inactive metabolites. It is about 90% bound to
plasma proteins. It is excreted as unchanged
drug and metabolites in the bile and urine.
Adverse effects are headache, sinus
abnormality, cough, pharyngitis, diarrhoea,
rhinitis, urinary tract infection, rash, anxiety/
nervousness, and muscle cramp. However,
most side effects have been mild and
transient in nature. Rare cases of
hypersensitivity reaction, occasionally severe
(e.g. anaphylaxis), have been reported.
It is indicated in mild to moderate
hypertension, either alone or in combina-
tion with other antihypertensive agents.
CALCIUM CHANNEL BLOCKERSCalcium channel blockers interfere with the
calcium entry into the myocardial and vascu-
lar smooth muscles and thereby decreasing the
availability of the intracellular calcium.
Calcium channel blockers depress the
contractility of the myocardium and decrease
the cardiac work and the requirement of
oxygen. This effect proves to be beneficial in
the treatment of angina pectoris.
VERAPAMIL
It increases coronary blood flow and
causes vasodilatation. It has anti-
arrhythmic action also and it decreases
peripheral vascular resistance.
After oral administration it is bound to
plasma proteins and it is metabolised to
biologically active metabolite.
Adverse effects include nausea, constipa-
tion, hypotension, flushing, dizziness, vertigo,
pedal edema, nervousness and paraesthesias.
It is indicated in tachycardias, such as
paroxysmal supraventricular tachycardia,
atrial fibrillation/flutter with tachya-
rrhythmia, extra systoles, hypertensive cri-
sis, acute coronary insufficiency (spasm),
angina pectoris, vasospastic angina, myocar-
dial infarction and hypertension.DILTIAZEM
Diltiazem is a calcium ion influx inhibi-
tor which inhibits the transmembrane in-
flux of calcium ions into cardiac muscle
and smooth muscle without changing
serum calcium concentration.
Diltiazem is well absorbed from gastro-
intestinal tract and is subject to extensive
first pass metabolism. It is 70% bound to
plasma proteins. It is excreted as metabolites
in bile and urine.
Adverse effects include headache ankle
edema, hypotension, dizziness, flushing,
weight gain, nausea, GI disturbances includ-
ing anorexia, nausea, vomiting, constipation
diarrhoea and taste disturbances. Occasionally
there is gingival hyperplasia, skin rash and
transient elevation in liver enzyme values.
It is indicated in the treatment of mild
to moderate essential hypertension and in
the management of chronic stable angina
and angina due to coronary artery spasm.NIFEDIPINE
It causes coronary vasodilatation and
increases coronary blood flow. It reduces the
total peripheral vascular resistance and
systolic and diastolic blood pressure is
reduced. It causes reflex tachycardia.
Adverse effects include headache, flushing,
palpitation, nausea, vomiting and edema.
It is indicated in vasospastic angina,
chronic stable angina, hypertension, hyper-
tensive emergency, hypertrophic cardiomy-