Pharmacology for Dentistry

Antianginal Agents 187

charge causing tachycardia and in-

creased cardiac contractility. So, palpi-

tation are felt.

6. Methaemoglobinemia: Its a rare ad-
   verse effect.
   Methaemoglobin has very low affinity
   for oxygen, so large doses of nitrites can
   result in pseudocyanosis (reduced O 2
   carrying capacity), tissue hypoxia and
   death.
   Usually, even large doses of GTN and
   other organic nitrates do not raise
   plasma levels of nitrite dangerously
   high.


7. Fainting: Venodilatation leads to
   increased capacity (venous pooling)
   leading to marked hypotension. This
   can cause syncope/temporary loss of
   consciousness.

Indications

Sublingual tablet: Angina pectoris.

Intravenous: Unstable angina, coronary
vaso-spasm, left ventricular failure accom-
panying MI, hypertension and during car-
diac surgery.

Ointment/transdermal patch: Prevention of
angina pectoris.

ISOSORBIDE DINITRATE

It can be given sublingually and orally
for treatment of angina. Mechanism of action
is same as nitrates.

Adverse effects include throbbing head-
ache, sweating, skin rash, palpitation, flush-
ing, weakness and dizziness.

It is indicated in acute attacks
(sublingually) and chronic prophylaxis
(orally) of angina pectoris and coronary in-
sufficiency. In acute myocardial infarction,
CHF and acute LVF.

ISOSORBIDE-5-MONONITRATE

It has a longer duration of action and

mechanism of action is same as nitrates.

After oral administration hepatic first pass

metabolism is less than isosorbide dinitrate,

hence, systemic bioavailability is more.

It is indicated in pulmonary hyperten-

sion, prophylaxis of angina pectoris, post

myocardial infarction therapy, CHF and

acute LVF. It is not recommended for acute

attacks of angina.

ERYTHRITYL TETRANITRATE

It is used for chronic prophylaxis of an-

gina pectoris. Tolerance may develop to

pharmacological actions.

Adverse effects include flushing, head-

ache, dizziness, methaemoglobinaemia and

drug rash.

It is indicated in treatment and prophy-

laxis of exertional and vasospastic angina.

PENTAERYTHRITOL

TETRANITRATE

It is used for chronic prophylaxis of an-

gina pectoris. Tolerance may develop to

pharmacological actions.

Beta blockers, calcium channel blockers

and potassium channel openers detailed

pharmacology is given in chapter ‘Antihy-

pertensive drugs’.

OTHER ANTIANGINAL DRUGS

DIPYRIDAMOLE

It is a coronary dilator and claimed to di-

late coronary resistance vessels. It probably