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Chapter 10

Chapter 10

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CHEM 1004
Gerald Buchanan

Chapter 10 - Major and Minor Tranquilizers ● Also called “anti-anxiety agents”. Useful to calm anxious patients before surgery and to help people with insomnia (can’t sleep) Minor Tranquilizers ● Many are benzodiazepines ● Note chemical structure-have benzene ring (benzo) and an attached 7-membered ring containing 2 N atoms (diaza) ● Most common are Xanax, Librium, Valium, Ativan-for daytime use ● As sleeping aids: Restoril, Halcion ● Librium - Had tranquilizing effects, but not as strong as major tranquilizers ● Librium and Valium are both Benzodiazepines ● GABA: Gamma Amino Butyric Acid ○ Inhibits neurotransmission in the brain ○ Blocks the arousal of ᾿higher’ brain centres ○ GABA receptor is a macromolecular complex ○ In addition to binding GABA, it has binding sites for drugs such as the BDA’s ● BDA’s make the GABA receptor site more efficient ● Open up the Cl- channel ● Results in increased chloride ion concentration in the postsynaptic neuron ● Makes this neuron ᾿less excitable’ ● Result of BDA’s: Decreased excitation of many nerve systems, reduced anxiety, diminished alertness and an increase in the threshold of convulsion ● Other Minor Tranquilizers: ○ These have a propanediol /carbamate type structure ○ Equanil, Miltown; mechanism of action not known completely ○ Lower therapeutic indices than BDA’s , so use has declined recently ● Benzodiazepine (BDA) receptors are located primarily in the brain, hence these drugs have no effect on the heart or skeletal muscles ● Most 1/2s are 1-3 days (ie Valium) ● Those used as sleeping pills have shorter values: ie Halcion is an important drug here, with a t1/2 of ca 3 hours. ● Small doses (~0.1 to 0.5 mg) leave little if any daytime sedation ● Halcion: ○ Also called triazolam (generic name) ○ Largely ineffective after 2 weeks of continued use ○ Not for use if pregnant, it is teratogenic ○ Adverse effects: amnesia, suicidal behaviour, agitation, ○ Also ᾿rebound insomnia’ can occur with drugs having short half lives ○ User can be worse off than before treatment and will take higher doses and become dependent on the drug ○ Don’t combine Halcion and alcohol ● Rebound Insomnia - Can occur following discontinuation of use of some BDA’s (with short half lives) for treatment of primary insomnia. Results in sleep quality that is worse than that experienced before use of the drug! Comparison to Barbiturates ● Barbiturates are older drugs used as ᾿minor tranquilizers’ but, major abuse potential, since these drugs depress respiration ● BDA’s are ᾿safer’ since they do not significantly depress respiration ○ BUT this is NOT true if BDA’s are combined with alcohol ● Sleep inducing drugs ○ Heavily in demand ○ Ambien and Lunesta are popular BDA Tolerance ● Tolerance to BDAᾼs can occur, resulting in the need for higher doses ● Prolonged higher dosage can produce physical dependence and withdrawal symptoms if treatment is stopped ● Withdrawal Symptoms: ○ Anxiety, restlessness, tremors, nausea, cramps ○ Also paranoia and disorganized irrational thinking ○ NB. Typical Valium dose is 2-10 mg (2-4 x daily). So, up to 40 mg /day possible and 20 weeks needed for withdrawal Minor Tranquilizer-drug Interactions ● Oversedation can occur if BDA’s are combined with alcohol ● Halcion combined with alcohol (often used by long distance travellers to promote sleep), can cause amnesia Benzodiazepines (BDA’s) in the Environment ● When a person takes a drug, the entire dose does not get absorbed by the body ● Some of the original drug, along with its metabolites, gets excreted ● Ends up in wastewater and can enter the natural water supply ● Effects Fish: Fish became more active, ate at a faster rate than normal, less interaction with other fish Major Tranquilizers ● Include antipsychotics, drugs for manic depression, treating acute alcoholism or geriatric agitation ● Chlorpromazine - developed in France. 1st successful use in 1950’s ● Revolutionized the treatment of these types of mental illness ● Reserpine ○ Reserpine is found in the root of the plant ᾿Rauwolfia Serpentina’ ○ Known by ancient Hindus of India for treatment of insanity and hypertension ○ Plant was ᾿ rediscovered῀ in 1930ᾼs and the active ingredient extracted in late 1950ᾼs ○ Effective antipsychotic drug, but use has declined due to adverse side effects ● Chlorpromazine ○ Used as an anesthetic booster in intravenous doses of 50-1
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