BARBITURATES AND RELATED DRUGS PCL .pptx

BARBITURATES AND RELATED DRUGS PCL .pptx

1. BARBITURATES AND RELATED DRUGS

2. COURSE OUTLINES Barbiturates Actions Pharmacokinetics of Barbiturates Adverse effects Contraindications Benzodiazepines

3. Barbiturates Popular hypnotics and sedatives before 1960 They are the first prototype of CNS depressants

4. Pharmacological actions Action on CNS They produce dose dependent effects Sedation sleep anesthesia coma Hypnotic dose (100-200mg) of a short acting barbiturates. The sleep is arousable, subject may feel confused and unsteady if woken early. Night awakening is reduced. REM and stage 3,4 sleep are decreased. A rebound increase in REM sleep and nightmares is often noted when the drug is abruptly discontinued and may take several days for normal sleep to be restored

5. Hangover may occur in the morning after a nightly dose Sedative dose (smaller dose of a longer acting barbiturate) given a day time can produce drowsiness, reduction in excitability and anxiety. Barbiturates can impair learning, short term memory and judgement Barbiturates have anticonvulsant activity Barbiturates do not have antitussive effect.

6. Effects of hypnotic doses of barbiturates on systems The respiratory system; neurogenic, hypercapneic and hypoxic drives to respiratory centre are depressed in succession. CVS: barbiturates doses produce a slight decrease in BP and heart rate Skeletal muscle: it has little effect but anesthetic doses reduce muscle contraction. Smooth muscle: tone and motility of bowel is decreased slightly Kidney: it tends to reduce urine flow by decreasing BP and increasing ADH release. Oliguria attends barbiturate intoxication.

7. Pharmacokinetics of Barbiturates Barbiturates are well absorbed from the git, widely distributed in the body. The rate of entry into CNS dependent on lipid solubility Highly lipid soluble substances like thiopentone penetrate easily while phenobarbitone enters very slowly Drugs with intermediate solubility are metabolised in the liver by oxidation, dealkylation and conjugation.

8. Activities Except for phenobarbitone which is used in epilepsy and thiopentone in anesthesia, they are rarely used today. Adverse effects include hangover, idiosyncracy , porphyria in susceptible individuals. Rashes and swelling of eyelids Physical dependence and considerable abuse liability Withdrawal syndromes

9. Barbiturate poisoning Gastric lavage and supportive measures. Haemodialysis and heamoperfusion Barbiturates interact with many drugs including warfarin, chloramphenicol, steroids, sodium valproate, phenytoin, imipramine and griseofulvin

10. BENZODIAZEPINES They are sedative-hypnotic drugs Examples include diazepam, lorazepam and midazolam They are used in anesthetic procedures They vary in their solubility Flumazenil can be used to counteract the effect of benzodiazepines