Pharmacology for Dentistry

Sympatholytics (Antiadrenergic Agents) 147

alpha receptors. Ergotamine is an important
alkaloid that possesses both vasoconstrictor
and alpha-receptor blocking activity. Both
ergotamine and dihydroergotamine are used
in the treatment of migraine.

MIGRAINE

Migraine is a severe episodic throbbing or
dull pain in head, may be lateralized or
generalised associated with anorexia,
nausea, vomiting, photophobia and blur-
ring of vision. The pain of migraine and
vascular headaches are associated with va-
sodilatation, edema and visible pulsations
of the extracranial blood vessels. The 5-HT
plays a pivotal role in pathophysiology of
migraine.

DRUG THERAPY OF MIGRAINE

a. Simple analgesics (aspirin or
paracetamol), NSAIDs and antiemetics are
useful in mild attacks of migraine.

b. Moderate and severe attacks of
migraine besides NSAIDs need specific
drugs like ergot alkaloids, sumatriptan and
methysergide along with antiemetics.

METHYSERGIDE

It is a 5-hydroxytryptamine antagonist
(5HT2A/2C). It is effective in preventing an
attack of migraine. Adverse effects include
nausea, abdominal pain, diarrhoea and ner-
vousness.

SUMATRIPTAN

It is a potent selective 5-HT1D receptor
agonist used in the treatment of migraine.
The 5HT1D receptor is found dominantly in
cranial blood vessel. It activates other

subtype of 5-HT 1 receptor at very high

concentration.

Oral bioavailability is only 15% but af-

ter SC injection absorption is rapid and com-

plete. It is metabolized by MAO-A isoen-

zyme and metabolites are excreted in urine.

Adverse effects include tightness in head

and chest, paresthesia in limb, dizziness, rise

in BP and bradycardia. Rarely seizures and

hypersensitivity reactions occur.

Dose: SUMINAT; 25-100 mg/day, 6 mg SC.

Drugs useful in prophylaxis of migraine

are β-adrenergic blockers (usually

propranolol), methysergide, calcium

channel blockers.

OTHER (^) ααααα-INHIBITORS

PRAZOSIN

It is an piperazinyl quinazoline effective in

the management of hypertension. It is highly

selective for α 1 receptors. It also reduces the

venous return and cardiac output. It is used

in essential hypertension, benign prostatic

hypertrophy and in Raynaud’s syndrome.

Prazosin lowers blood pressure in human

beings by relaxing both veins and resistance

vessels but it dilates arterioles more than

veins.

It has variable absorption from GIT and

has about 50% hepatic first pass metabolism.

It is highly bound to plasma proteins.

Adverse effects include orthostatic

hypotension, dizziness, headache, drowsiness,

weakness, palpitation and impotence.

TERAZOSIN

It is similar to prazosin but has higher

bioavailability and longer plasma t½.