Pharmacology for Dentistry

Sedative & Hypnotics 71

• For general anaesthesia: Ultra short
  acting barbiturates are used.


• As preanaesthetic medication.


• As obstetrical analgesia.

Barbiturate Poisoning

It produces severe toxic manifestations.
Either suicidal or accidental intake of toxic
doses of barbiturates is characterized by
depressed respiration, circulatory shock,
pupils are initially constricted & then dilated
due to asphyxia, hypothermia, renal failure
and pulmonary complications such as acute
pulmonary edema.

Treatment of Acute Barbiturate Poisoning

• Gastric lavage to remove unabsorbed
  drug. Emesis can be produced by
  apomorphine and activated charcoal is
  administered to adsorb the unabsorbed
  drug.


• Maintenance of respiration:
  
  Oxygen inhalation.
  
  Endotracheal intubation or tracheo-
  stomy.
  
  Mechanical ventilation.


• Intravenous fluids.


• Forced diuresis: Diuretics like mannitol
  and furosemide can be used.


• Alkalinization.


• Prophylactic antimicrobial therapy to
  avoid any secondary infection e.g.
  pneumonia and infection due to
  tracheostomy or urinary catheterization.


• Dialysis (peritoneal or haemodialysis).

BENZODIAZEPINES

Benzodiazepines are commonly used
anxiolytics in clinical practice because these

agents exhibit good efficacy, are relatively

safe and have minimum toxicity. They are

indicated for short term relief of anxiety.

Benzodiazepines have no action on respira-

tion and cardiovascular system. They have

no action on other body systems. They have

a muscle relaxant action, probably due to

CNS depressant action and have anticonvul-

sant action. They have lower abuse liabil-

ity. Benzodiazepines when administered

cause sedation, hypnosis, muscle relaxation,

relieve anxiety and some have anticonvul-

sant action.

Benzodiazepines exert their pharmaco-

logical effect mainly by potentiation of

neural inhibition in CNS which is medi-

ated by GABA.

Pharmacokinetics

The pharmacokinetic profile is different

with different compounds. Diazepam after

oral administration is completely and rap-

idly absorbed from the proximal small in-

testine. Oxazepam is least rapidly absorbed

while lorazepam is an intermediately ab-

sorbed between these two. They are

metabolised in liver by dealkylation and

hydroxylation and excreted in urine as glu-

curonide conjugates. They cross the placen-

tal barrier and are secreted in milk.

Adverse Reactions

The common side effects are drowsiness,

lethargy, ataxia. They also cause behavioural

changes and dose dependent impairment of

visual motor coordination. Other side effects

which occur rarely are vertigo, headache,

allergy, photosensitization, leucopenia, im-

paired sexual function and menstrual irregu-

larities.