70 Section 2/ Drugs Acting on CNSLiver: They induce microsomal drug
metabolising enzyme thus they increase the
rate of metabolism of number of drugs.
Pharmacokinetics
They are well absorbed from the GIT.
They are widely distributed in body. Rate
of entry into CNS is dependent on lipid solu-
bility. Ultra short acting barbiturates are
highly lipid soluble and quickly enter the
brain. Redistribution to various tissues ter-
minate their action and they are slowly re-
leased from the tissues and gradually
metabolised in the liver. They are partly
metabolised and partly excreted unchanged
in urine.
Adverse Effects
Intolerance effects include headache,
vomiting, diarrhoea, nausea.
Hangover especially with long acting
barbiturates. Excitement and restlessness,
neuralgic pain, allergic reactions include
swelling and erythematous dermatitis. They
produce physical dependent and have abuse
potential.Therapeutic Uses- To produce hypnosis.
- To produce sedation.
- Anticonvulsant action: Phenobarbital is
drug of choice.
Table 2.2.1: Classification of sedative and hypnotics.
I. Barbiturates
Phenobarbitone (LUMINAL) 15-30 mg TDS (as sedative)
60-100 mg HS (as hypnotics)
Butobarbitone (SONERYL) 15-30 mg TDS, 100-200 mg HS
Pentobarbitone (NEMBUTAL) 30 mg TDS, 100 mg HS
Secobarbitone (LIPATON) 30 mg TDS, 100 mg HS
II. Benzodiazepines
i. Used as hypnotics
Diazepam (CALMPOSE) 5-10 mg HS
Nitrazepam (NITROSUN) 5-10 mg HS
Midazolam (FULSED) 0.02-0.1 mg/kg/hr IV infusion
ii. Used as antianxiety agents
Diazepam (CALMPOSE) 2-10 mg BD-TDS
Chlordiazepoxide (LIBRIUM) 10-25 mg BD-TDS
Lorazepam (TRAPEX) 1-2 mg BD-TDS (oral/IM)
Alprazolam (ALPRAX) 0.5-4 mg/day
Oxazepam (SEREPAX) 15-30 mg OD-TDS
iii.Used as antiepileptic agents
Diazepam 10-25 mg/day IM/IV
Clonazepam (CLONOTRIL) 0.5-4 mg TDS
III.Newer nonbenzodiazepine compounds
Zopiclone (ZOPICON) 7.5 mg HS
Zolpidem (SOBRIUM) 10 mg HS
Zaleplon (ZAPLON) 10 mg HS