EFFECT OF DRUGS AND CHEMICALS ON SALIVARY SECRETION

EFFECT OF DRUGS AND CHEMICALS ON SALIVARY SECRETION

Substances which increase salivary secretion

1. Sympathomimetic drugs like adrenaline and ephedrine.

2. Parasympathomimetic drugs like acetylcholine, pilocarpine, muscarine and physostigmine.

3. Histamine.

Substances which decrease salivary secretion

1. Sympathetic depressants like ergotamine and dibenamine.

2. Parasympathetic depressants like atropine and scopolamine.

3. Anesthetics such as chloroform and ether stimulate the secretion of saliva. However, deep anesthesia

decreases the secretion due to central inhibition.

HYPOSALIVATION

Reduction in the secretion of saliva is called hyposalivation. It is of two types, namely temporary

hyposalivation and permanent hyposalivation.

1. Temporary hyposalivation occurs in:

i. Emotional conditions like fear.

ii. Fever.

iii. Dehydration.

2. Permanent hyposalivation occurs in:

i. Sialolithiasis (obstruction of salivary duct).

ii. Congenital absence or hypoplasia of salivary glands.

iii. Bell palsy (paralysis of facial nerve).

HYPERSALIVATION

Excess secretion of saliva is known as hypersalivation. Physiological condition when hypersalivation occurs is pregnancy. Hypersalivation in pathological conditions is called ptyalism, sialorrhea, sialism or sialosis. Hypersalivation occurs in the following pathological conditions:

1. Decay of tooth or neoplasm (abnormal new growth or tumor) in mouth or tongue due to continuous

irritation of nerve endings in the mouth.

2. Disease of esophagus, stomach and intestine.

3. Neurological disorders such as cerebral palsy, mental retardation, cerebral stroke and parkinsonism.

4. Some psychological and psychiatric conditions.

5. Nausea and vomiting

OTHER DISORDERS

In addition to hyposalivation and hypersalivation, salivary secretion is affected by other disorders also,

which include:

1. Xerostomia

2. Drooling

3. Chorda tympani syndrome

4. Paralytic secretion of saliva

5. Augmented secretion of saliva

6. Mumps

7. Sjögren syndrome.

1. Xerostomia

Xerostomia means dry mouth. It is also called pasties or cottonmouth. It is due to hyposalivation or absence of salivary secretion (aptyalism).

Causes

i. Dehydration or renal failure.

ii. Sjögren syndrome (see below).

iii. Radiotherapy.

iv. Trauma to salivary gland or their ducts.

v. Side effect of some drugs like antihistamines, antidepressants, monoamine oxidase inhibitors,

antiparkinsonian drugs and antimuscarinic drugs.

vi. Shock.

vii. After smoking marijuana (psychoactive compound from the plant Cannabis).

Xerostomia causes difficulties in mastication, swallow ing and speech. It also causes halitosis (bad breath; exhalation of unpleasant odors).

2. Drooling

Uncontrolled flow of saliva outside the mouth is called drooling. It is often called ptyalism.

Causes

Drooling occurs because of excess production of saliva, in association with inability to retain saliva within the mouth.

Drooling occurs in the following conditions:

i. During teeth eruption in children.

ii. Upper respiratory tract infection or nasal allergies

in children.

iii. Difficulty in swallowing.

iv. Tonsillitis.

v. Peritonsillar abscess.

3. Chorda Tympani Syndrome

Chorda tympani syndrome is the condition characterized by sweating while eating. During trauma or surgical procedure, some of the parasympathetic nerve fibers to salivary glands may be severed. During the regeneration, some of these nerve fibers, which run along with chorda tympani branch of facial nerve may deviate and join with the nerve fibers supplying sweat glands. When the food is placed in the mouth, salivary secretion is associated with sweat secretion.

4. Paralytic Secretion of Saliva

When the parasympathetic nerve to salivary gland is cut in experimental animals, salivary secretion

increases for first three weeks and later diminishes; finally it stops at about sixth week. The increased

secretion of saliva after cutting the parasympathetic nerve fibers is called paralytic secretion. It is because

of hyperactivity of sympathetic nerve fibers to salivary glands after cutting the parasympathetic fibers. These hyperactive sympathetic fibers release large amount of catecholamines, which induce paralytic secretion. Moreover, the acinar cells of the salivary glands become hypersensitive to catecholamines after denervation. The paralytic secretion does not occur after the sympathetic nerve fibers to salivary glands are cut.

5. Augmented Secretion of Saliva

If the nerves supplying salivary glands are stimulated twice, the amount of saliva secreted by the second

stimulus is more than the amount secreted by the first stimulus. It is because, the first stimulus increa ses

excitability of acinar cells, so that when the second stimulus is applied, the salivary secretion is augmented.

6. Mumps

Mumps is the acute viral infection affecting the parotid glands. The virus causing this disease is paramyxovirus. It is common in children who are not immunized. It occurs in adults also. Features of mumps are puffiness of cheeks (due to swelling of parotid glands), fever, sore throat and weakness. Mumps affects meninges, gonads and pancreas also.

7. Sjögren Syndrome

Sjögren syndrome is an autoimmune disorder in which the immune cells destroy exocrine glands such as

lacrimal glands and salivary glands. It is named after Henrik Sjögren who discovered it. Common symptoms of this syndrome are dryness of the mouth due to lack of saliva (xerostomia), persistent cough and dryness of eyes. In some cases, it causes dryness of skin, nose and vagina. In severe conditions, the organs like kidneys, lungs, liver, pancreas, thyroid, blood vessels and brain

are affected.