STUDY UNIT 2.2-SEDATIVE-HYPNOTICS 

• What does anterograde amnesia mean and which drugs can cause this effect?

Anterograde amnesia, is the inability to remember events that occur during the drugs duration of action. Anterograde amnesia is caused by all benzodiazepines that are indicated for hypnosis to some degree. Some examples include; Lorazepam, temazepam, quazepam etc. 

• Name the effects of the sedative-hypnotic drugs on the normal sleep pattern and explain their significance to the patient.
  • • Decrease the time that it takes to fall asleep.
    • If the patient sleeps for less than 6 hours a night, it would increase total sleep duration.
    • Has a small suppressant effect on REM sleep, high dosages would increase suppression of phase 2 non-REM sleep
    • High dosages would also decrease the duration phase 4 non-REM sleep
    • If stopped, negative effects will be seen.

• Which of the sedative-hypnotic drugs are used as a supplementary therapy in anaesthesia?  Can you explain why?

Benzodiazepines such as diazepam which has useful relaxant effects in skeletal muscle spasticity, Lorazepam to supress the symptoms of delirium tremens.

Phenobarbital can also be used in progressively decreasing doses to patients during withdrawal from physiologic dependence on ethanol or other sedative-hypnotics.

• Which of the sedative-hypnotic drugs are used as anticonvulsants?

Benzodiazepines and Barbiturates

• What is the mechanism of the muscle-relaxing effects of some of the carbamates and the BDs?

Exertion of inhibitory effects on polysynaptic reflexes and internuncial transmission and at high doses may also depress transmission at the skeletal neuromuscular junction. Selective actions of this type lead to muscle relaxation.

• Discuss the effects of the sedative-hypnotic drugs on the respiratory and cardiovascular systems.

Respiratory:

At hypnotic doses in healthy patients, the effects on respiration are comparable to changes during the natural sleep pattern. Although, in patients with pulmonary disease, even at therapeutic doses, sedative-hypnotics can cause significant respiratory depression. Effects on respiration are dose related and depression of the medullary respiratory centre is the usual cause of death due overdose of sedative-hypnotics.

Cardiovascular:

In healthy patients, there are no significant effects observed on the cardiovascular system at doses up to those causing hypnosis. 

However, in hypovolemic states, heat failure and other diseases that impair cardiovascular function, normal doses of sedatives may cause cardiovascular depression, probably as a result of actions on the medullary vasomotor centres. 

At toxic doses, myocardial contractility and vascular tone may both be depressed by central and peripheral effects, possibly via facilitation of the cations of adenosine, leading to circulatory collapse. 

Respiratory and cardiovascular effects are more marked when sedative-hypnotics are given intravenously.