Pharmacology for Dentistry

172 Section 4/ Drugs Acting on Cardiovascular & Urinary System

ing of the cardiac glycosides to Na+ K+-AT-
Pase. Infuse KCl 20 mmol/hr intravenously
or orally depending upon the case.

Supraventricular Arrhythmias
Can be treated by beta blockers e.g.
propranolol 10-40 mg every 6 hourly orally
or 0.5-1 mg IV.

Ventricular Arrhythmias
Lignocaine (1-2 mg/kg IV) is the drug
of choice. Phenytoin is also useful (250 mg
IV) and has the added advantage of
countering the depression of AV conduction
by digitalis.

AV Block and Bradycardia
Can be treated by atropine (0.6-1.2 mg IM).

Therapeutic Uses

Digitalis is used therapeutically in the
treatment of:

Congestive Heart Failure

Digitalis increases stroke volume and
cardiac output. Digitalis by increasing the
cardiac output, brings about more complete
emptying of the ventricles during systole.
This reduces the pulmonary congestion and
edema and decrease in systemic venous
pressure. The cardiac glycosides primarily
correct systolic dysfunction.

The dosing schedule is dependent on the
desired speed of action and urgency. Like
other drugs having a longer duration of ac-
tion the treatment is initiated with a load-
ing dose which is followed by maintenance
dose for achieving a rapid onset of action
and to avoid cumulative toxicity.

The maintenance dose is the amount
required to maintain the therapeutic effect

and is equal to the amount eliminated

during the day.

Methods of Digitalization

1. Intravenous digitalization is done in
   emergency conditions of CHF or in atrial
   fibrillation. Digoxin 0.25 mg followed by
   0.1 mg hourly be given by slow IV route
   with close monitoring of cardiac function.


2. Oral digitalization: Digoxin 0.5-1.0 mg
   stat and followed by 0.25 mg 6 hourly
   with monitoring of toxicity.
   
   
   • Digitoxin 1.2 mg is administered as
     a single dose. This can be given in
     divided dose also, in 8 hours interval.
   
   
   
   


3. Maintenance dose method: Administration
   of a daily maintenance dose (0.5 mg) of
   digoxin will digitalise the patient within
   a week.

Atrial Fibrillation

Digitalis is the drug of choice in atrial

fibrillation for controlling ventricular rate.

Its effect is due to the prolongation of the

refractory period of the conducting tissue.

The dose in so adjusted as to maintain the

ventricular rate of 60 to 80 beats per minute

at rest and approximately 100 beats per

minute during light exercise.

Atrial Flutter

The reversal to normal rhythm is

because digitalis converts flutter into

fibrillation. Digitalis enhances the AV block

and reduces the ventricular rate.

Paroxysmal Supraventricular

Tachycardia

Its effects is due to vagomimetic activity,

generally one fourth total IV digitalizing