Pharmacology for Dentistry

Sympathomimetics (Adrenergic Agents) 135

antagonist of histamine (a known mediator
of many hypersensitivity reactions). It is
used in bronchial asthma, acute angion-
eurotic edema, acute hypersensitivity reac-
tion to drugs and in the treatment of ana-
phylactic shock.

Bronchial asthma: When given
subcutaneously or by inhalation, adrenaline
is a potent drug in the treatment of status
asthmaticus.

Cardiac uses: Adrenaline may be used
to stimulate the heart in cardiac arrest.
Adrenaline can also be used in Stokes-Adam
syndrome, which is a cardiac arrest
occurring at the transition of partial to
complete heart block. Isoprenaline or
orciprenaline may be used for the temporary
treatment of partial or complete AV block.

Vascular uses: Pressor agents like
adrenaline (more appropriate dopamine or
dobutamine) may be useful in hypotensive
crisis.

Adrenaline along with local anaesthetics
may be used for infiltration, nerve block and
spinal anaesthesia for prolonging the action
and to reduce the systemic toxicity of local
anaesthetics.

Adrenaline may be useful in control of
haemorrhage from the skin and mucous
membrane such as epistaxis and after tooth
extraction.

Also used as nasal decongestant.

Miscellaneous uses:

a. Phenylephrine is used in fundus

examination as mydriatic agent.

b. Amphetamines are sometime used as

adjuvant and to counteract sedation

caused by antiepileptics.

c. Anoretic drugs can help the obese

people.

d. Amphetamine may be useful in

nocturnal enuresis in children.

e. Isoxsuprine (uterine relaxant) has been

used in threatened abortion and

dysmenorrhoea.

DOPAMINE

It is an immediate metabolic precursor of

noradrenaline. It activates D 1 receptors in

several vascular beds, which causes

vasodilatation. It acts on dopaminergic and

other adrenergic receptors (α & β 1 ).

Pharmacological Actions of Dopamine

The actions of particular sympathomi-

metic amine depend on its relative activity

at different types of adrenergic receptors.

The overall actions are:

Cardiovascular system:

a. Blood vessels: D 1 receptors promote

vasodilatation of renal, splanchnic,

coronary and cerebral arteries.

Activation of the D 1 receptors in the

renal vasculature may play a major role

in the natriuresis induced by

pharmacologic administration of

dopamine.

b. Heart: In the heart, intraventricular

pressure rises and falls more rapidly,

and ejection time is decreased. These

direct effects are easily demonstrated

in the absence of reflexes evoked by

changes in blood pressure, e.g. in

isolated myocardial preparations and

in patients with ganglionic blockade. In

the presence of normal reflex activity,

the direct effects on heart rate may be