Lab 2 Barbiturates PDF

Assist. Lecturer: Nibras Hasaballah Jasem  Sedative-Hypnotic Drugs The sedative-hypnotics belong to a chemically heterogeneous class of drugs, almost all of which produce dose-dependent CNS depressant effects. Sedative is a drug that reduce excitement & calm the person Hypnotic...

Assist. Lecturer: Nibras Hasaballah Jasem  Sedative-Hypnotic Drugs The sedative-hypnotics belong to a chemically heterogeneous class of drugs, almost all of which produce dose-dependent CNS depressant effects. Sedative is a drug that reduce excitement & calm the person Hypnotic is a drug that produces sleep-resembling normal sleep A major subgroup is the Benzodiazepines, other including : Barbiturates and miscellaneous agents Sedative-Hypnotic Drugs  Principle Sedation: Reduction of anxiety Addiction: thestate of response to a drug whereby the drug taker feels compelled to use the drug and suffers anxiety when separated from it Anesthesia : Loss of consciousness associated with absence of response to pain Anxiolytic : A drug that reduces anxiety, a sedative agent  Terms to Learn Dependence: the state of response to a drug whereby removal of the drug evokes unpleasant, possibly life-threatening symptoms, often the opposite of the drug’s effects. REM sleep: phase of sleep associated with rapid eye movements; most dreaming takes place during REM sleep. Tolerance:reduction in drug effect requiring an increase in dosage to maintain the same response  Types of Neurotransmitter  ExcitatoryN.T : 1. Acetylcholine 2. Glutamate  Inhibitory N.T : 1. GABA 2. Glycine  Barbiturates Phenobarbital: long acting Secobarbital: short action Thiopental: ultra short acting  Mechanism of Action Barbiturates depress neuronal activity in the midbrain reticular formation, facilitating and prolonging the inhibitory effects of GABA receptor. Barbiturates also bind to multiple isoforms of the GABA A receptor Barbiturates increase the duration of GABA- mediated chloride (influx of Cl ion) channel opening (hyperpolarization) Barbiturates may also block the excitatory transmitter glutamic acid, and at high concentration, sodium channels.  Barbiturates + GABA receptor Activation of GABA receptor Opening of Chloride channel Increase the duration of GABA gated channel opening Hyperpolarization of cells CNS depression GABA - receptor  Clinical Applications Anesthesia (thiopental) Insomnia and sedation (secobarbital) Seizure disorders (phenobarbital) CNS depressant  Pharmacokinetics Most sedative-hypnotic drugs are lipid-soluble and are absorbed well from the gastrointestinal tract, with good distribution to the brain. The CNS effects of thiopental are terminated by rapid redistribution of the drug from brain to other highly perfused tissues. Renal excretion  Adverse effects Drowsiness, severe respiratory & cardiovascular depression. Tolerance Dependence liability> benzodiazepine Enzyme induction may lead to multiple drug interactions Withdrawal symptoms is much more sever than opioid and can results in death ( no antidote ). C.I. in pregnancy  Methods 1- Check the weight of two mice / rats. 2-Inject one animal with normal saline I.P and mark it as control, and another animal with Phenobarbital I.P or S.C in a dose of 50 mg/kg. 3- Inject one animal with normal saline I.P and mark it as control, and another animal with Thiopental I.P or S.C in a dose of 30 mg/kg. 4-Record the observations and time of occurrence in a table form.