PHARMACOLOGICAL CONTROL OF CNS

Question 1

Where can drugs act to influence respiratory function? [2]

Answer 1

• The lungs
• The CNS

Question 2

There are both beneficial and adverse effects of using drugs to control respiratory function, what is something that can vary how they effect a person?

Answer 2

If the person has a respiratory condition, the drugs will affect them differently compared to someone who has normal lungs

Question 3

Name the 3 places in the brainstem that are potential targets for drug action [3]

Answer 3

• Peripheral chemoreceptors
• Central chemoreceptors
• Networks where synaptic neurotransmission

Question 4

What is another name for respiratory stimulants?

Answer 4

Analeptics

Question 5

Give an example of an analeptic

Answer 5

Doxapram

Question 6

Explain the pharmacokinetics of doxapram? [2]

Answer 6

Metabolism: Take less than 1 minute to come into effect because they are metabolised very quickly

Short half life: Can’t be used for the long term maintenance of a long term chronic condition because they have a short half life

Question 7

Explain the mechanism of doxapram? [3]

Answer 7

• Stimulates the chemoreceptors for CO2 and O2
• Non - specifically enhances electrical activity - acts on receptors everywhere
• Has adverse effects because it can act on receptors anywhere e.g cardiac arrhythmias, convulsions

Question 8

What are the clinical uses of Doxapram? [2]

Answer 8

Used in emergencies such as:

• Acute ventilatory failure with hypercapnia (COPD)
• Post -operative respiratory depression

Question 9

What is preferred over the use of Doxapram? [1]

Answer 9

Mechanically assisted respiration

Question 10

Give the definition of a respiratory depressant

Answer 10

Any agent which has a generalised CNS depressant effect and has the potential to depress respiration via action at the respiratory nuclei in the brain stem (medulla)

Question 11

What are 3 implications for the use of respiratory depressant drugs? [2]

Answer 11

• Can be used for legal/ therapeutic purposes
• Can be used illegally

Question 12

What are two things about patients that need to be taken into account when using respiratory depressants?

Answer 12

• Need to take into account how much of a reserve a patient has in their system
• Need to take into account their age - very young and very old patients are more sensitive to respiratory depression

Question 13

Give two examples of respiratory depressants [2]

Answer 13

• General anaesthetics
• Volatile anaesthetics - Isoflurane

Question 14

What is the physiological action of respiratory depressant general anaesthetic?

Answer 14

They decrease the response of CO2 chemoreceptors which would normally allow for the increase or normalisation of PaCO2. With general anaesthetics this is blocked

Question 15

What is the mechanism of action of respiratory depressant general anaesthetic?

Answer 15

• Bind to GABA receptors
• They are non specific and bind to GABA anywhere this is not avoidable and so oxygen needs to also be given alongside the depressant

Question 16

Name 5 types of respiratory depressants

Answer 16

• General anaesthetics
• Benzodiazepines
• Barbiturates
• Alcohol
• Opioids

Question 17

Name 2 benzodiazepines [2]

Answer 17

• Diazepam
• Temazepam