Drugs and the Nervous System Flashcards by Gen Parkinson

The nerve endings send impulses to the brain along what??

Axons

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What three areas do drugs target that constitute the nervous system?

Brain
Spinal Cord
Nerves

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Name 5 excitatory neurotransmitters (SANDG)

Noradrenaline
Dopamine
Serotonin (5-HT)
Acetylcholine
Glutamate

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Name 2 inhibitory neurotransmitters (beginning with G)

GABA

glycine

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Once the impulse/calcium enters the neuron in the brain, what does it release to the synapse?

Neurotransmitter

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Once the neurotransmitter has been released into the synapse, what are the two processes that can happen?

It is picked up by the postsynaptic receptor to go to the postsynaptic cell
It is picked up by enzymes in the postsynaptic cleft, where it goes to the reuptake receptor (to be recycled for the next impulse)

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What are the main drugs that act on the nervous system?

5 begin with A, 1 begins with N

Anaesthetics
Anxiolytic/hypnotic
Antidepressant
Antiparkinsonian
Anticonvulsants
Neuromuscular blocking

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General anaesthetics work mainly in the central nervous system (on parts of the brain). What are the 2 ways they can be administered?

Inhalation

Intravenously

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Is general anaesthetic lipid soluble?

Yes

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What 4 things does general anaesthetic promote/do?

Analgesia
Unconsciousness
Amnesia
Loss of reflexes

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General anaesthetic is lipid soluble so that it can cross the blood/brain barrier. Once it has done this, what are the 2 ways we think it may work?

Acting on membrane receptors to reduce excitability of neurones
Affecting ion channels (opening/closing)

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What are 6 typical side effects of general anaesthetic?

one is specific to pregnant women

Nausea/vomiting
Shallow/rapid breathing
Decreased cardiac output
Decreased kidney perfusion
Loss of temperature control
Crossing the placenta

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If a person is taking anticoagulant drugs and is due to undergo surgery using a general anaesthetic, what should they do?

Stop taking the drugs as it may interact with the anaesthetic

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There are two phases of anaesthesia, induction and maintenance.
How are these administered and what are the strengths and weaknesses of each?

Induction: intravenous - rapid unconsciousness, hard to reverse, needles

Maintenance: inhaled - no needles, easier to control, mask over face is claustrophobic

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There are 4 stages of anaesthesia. Stage 3 is surgical anaesthesia where skeletal muscle is relaxed and there is a loss of reflexes. We want the person to be in this stage for as long as possible.
What are the other 3 stages?

Stage 1: analgesia
Stage 2: excitement - adrenaline release
Stage 3: surgical relaxation
Stage 4: medullary paralysis - loss of respiratory/vasomotor control

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What are the 4 types of general anaesthetic?

Barbiturates
Non-barbiturates
Gases
Volatile liquids (administered through vaporiser)

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What is the name of the anaesthetic used to maintain anaesthesia (along with oxygen)?
This is a potent analgesic and must be used in combination with other drugs.

Nitrous Oxide

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What anaesthetic can damage a foetus if the mother has low level long-term exposure to it?

Nitrous Oxide

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Name 3 general anaesthetics that are inhaled and controlled by concentration of vapour:
(they all end in flurane)

Isoflurane
Desflurane
Sevoflurane

INHALED = FLURANE

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What are the side effects of inhaled anaesthetics?

CV depression
Hypotension
Arrhythmias
Decreased CSF pressure

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Is hypoxia a potential issue with inhaled anaesthetics?

Yes

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Name a non-barbiturate general anaesthetic:

INTRAVENOUS

Propofol

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Propofol can be used as a general anaesthesia for day procedures.
Why?

It has a rapid action and a rapid recovery, without ‘hangover’

Propofol can however cause convulsions/anaphylaxis

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Name a barbiturate general anaesthetic (one which has a very quick mechanism of action but only lasts 5-10 minutes)
INTRAVENOUS

Thiopental

Very useful for brief procedures as rapid awakening - issues with long lasting sedation however

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Etomidate is sometimes used in surgery as it has no hangover effect and causes less hypotension. What are the drawbacks of this?

Potential muscle movements in surgery and suppression of adrenocortical function

Ketamine is rarely used as a general anaesthetic, but what patient groups do we tend to use it on?

Shocked patients and children. We do this as it helps increase blood pressure Scared of horse stampeed

What are the side effects of using ketamine as a general anaesthetic?

Raised heart rate and blood pressure | Bad dreams/hallucinations in recovery

What are anxiolytics and hypnotics called? | When are they used?

Benzodiazepines - calm the patient before surgery

In surgery, what do neuroleptics and anti-emetics do?

Counteract side-effects of anaesthetic such as nausea

In surgery, why do we use antihistamines?

To prevent bronchi from constricting

In surgery, what is the purpose of analgesics (usually opioid)?

To sedate the patient

What do atropine and hyoscine do in surgery? | These are called anticholinergics

They block the effect of the Peripheral Nervous System to prevent the patient from choking

The first effect of a benzodiazepine is anxiety. As the dosage increases, what are the other two effects? SH

Sedation then Hypnosis

Which routes can benzodiazepines be administered?

Oral, intravenously, intramuscularly and rectal

What are midazolam, temazepam and diazepam (valium) examples of?

Benzodiazepines Benzos = PAM

Benzodiazepines have no analgesic effect and can result in hypotension/constipation. Why are they used in surgery or unpleasant procedures?

Benzos, or PAM causes amnesia and does not cause excessive sedation in a low dose

Describe the mechanism of action of benzodiazepines: | it involves GABA

BENZO - PAM - GABA Benzos increase GABA in the brain. GABA is a inhibitory neurotransmitter. The impulse sends out its own NTs from the synapse of cells, but at the same time, GABA is released from the synapse of other cells. GABA binds to the postsynaptic cell first to stop the response occurring from the other NT.

Benzodiazepines are hypnotics and can also be used to treat anxiety. It should only be used for acute anxiety due to 4 drawbacks. What are these?

May lead to dependence Can cause respiratory depression Interact with alcohol Can cross the placenta

What type of nerve do neuromuscular blocking drugs block? | And what are they also known as?

They block transmission of the MOTOR nerve. | Also known as MUSCLE RELAXANTS

Why are neuromuscular blocking drugs useful in surgery?

Reduce the need for really deep anaesthesia | Relax vocal chords allowing insertion of the tracheal tube

Do neuromuscular blocking drugs necessitate the need for assisted respiration during surgery?

Yes

What are two drawbacks of muscle relaxants?

Prolonged muscle paralysis/pain | Histamine release = bronchospasm

What neurotransmitter do muscle relaxant depolarising and non-depolarising blockers work with/against?

ACETYLCHOLINE (ACh) Polar = artic = a = Acetylcholine

What does ACh stand for?

Acetylcholine

How do ACh antagonists work?

They compete with ACh for the nicotinic receptors at the neuromuscular junction. They prevent the ACh binding to the receptor so that it cannot stimulate the muscle

Name two ACh antagonists: | cur

Atracurium (short acting) Pancuronium (longer acting) cur = cures the muscle moving

How is the action of ACh non-depolarising blockers reversed?

We increase the ACh concentration, by inhibiting acetylcholinesterase. Lots of ACh will over come the non-depolarising blocker. We can do this by giving a drug like neostigmine, which also breaks down the antagonist

What does neostigmine do?

Breaks down ACh antagonist and increases ACh concentration

What does acetylcholine do?

It is a neurotransmitter that stimulates muscle

How do depolarising blockers (ACh AGONISTS) work? | Remember these are also muscle relaxants.

They mimic ACh, but rather than stimulating the muscle, they produce sustained depolarisation of the muscle = paralysis. Sodium moves into the cell meaning it is permanently depolarised so it cannot respond to further action potentials from the ACh. PERMANENT contraction.

How can we administer an ACh agonist to prevent it being short acting?

Via a drip

What is suxamethonium? | What enzyme is it metabolised by?

Suxamethonium is a depolarising blocker (ACh agonist). | It is metabolised by pseudocholinesterase - so it can be naturally broken down by most people (not everyone has it)

What do narcotic analgesics do?

They act on the CNS opioid receptors to relive pain. Also euphoric - allow the patient to escape from reality.

Name some examples of narcotic (opioid) analgesics

Fentanyl, alfentanil, remifentanil, morphine FENTANIL and morphine for narcotics = Nil/Narcotic?

One side effect of a narcotic analgesic is reduced breathing rate. Name two more:

Risk of addiction | May cause nausea/vomiting

What two things are local anaesthetics used for?

Analgesia | Paralysis

Local anaesthetics are short acting and work on a specific nerve pathway. What is their mechanism of action?

They block the transmission of nerve impulses carrying pain signals from the nociceptors to the brain. Never gets to the spinal cord.

When are local anaesthetics usually used?

Minor surgical procedures

What is the proper name for pain receptors?

Nociceptors

What type of anaesthetic inhibits sodium entry through sensitive sodium channels, to block transmission of nerve impulses?

Local anaesthetic It stops the action potential forming at the site of pain - it the nerve cells cannot depolarise

What type of anaesthetic is administered into the epidural space (at the nerve roots), intradermally and topically (for minor pain)?

Local

What is a good way to remember names of local anaesthetics?

CAINE Lidocaine, prilocaine etc...

In what situation can local anaesthetic lead to the following: abnormal heartbeat, convulsions, restlessness, cardiorespiratory arrest

If the anaesthetic reaches the brain and heart (or hypersensitivity)

What types of drug: enhance potency and prolong the duration of action of other drugs, increase safety margin (toxicity), reduce local blood flow (lessening blood loss during surgery)

Vasoconstrictors

Are adrenaline and felypressin vasoconstrictors?

Yes

What kind of drug increases levels of excitatory neurotransmitters in the brain?

Antidepressants

What kind of drugs increase levels of the neurotransmitter dopamine?

Antiparkinsonian drugs

What types of drugs treat epilepsy by reducing the conduction of excitatory nerve impulses and/or increasing GABA activity?

Anticonvulsants

What are the 3 main types of antidepressant? TCA SSRI MAOI

tricyclic antidepressants selective serotonin re-uptake inhibitors monoamine oxide inhibitors

What is the mechanism of action for a TCA or SSRI antidepressant?

They bind to the reuptake receptor, so when neurotransmitters are released, they keep acting as they cannot be taken up again.

What is the mechanism of action for MAOI antidepressants?

They bind to a chemical that breaks down excitatory NTs so that more of them can go to the postsynaptic cell

What are imipramine, nortriptyline and doxepin examples of?

Tricyclic antidepressants NorTRI

What are fluoxetine, citalopram, sertraline and paroxetine examples of? (antidepressant you know best)

SSRIs

What are phenelzine and tranylcypromine examples of?

MAOI - monoamine oxidase inhibitors

What type of anti-depressant may cause dry mouth, blurred vision, constipation, urinary retention, arrhythmia, mental confusion and sedation?

Tricyclic antidepressants | This stops the uptake of three NTs

What type of anti-depressant can cause headaches, nausea, dizziness, diarrhoea and convulsions? (this is not the worst one)

Selective Serotonin Re-Uptake Inhibitors

What type of drug can cause nausea, dizziness and insomnia, and also interact with tyramine-containing foods such as red wine, cheese and marmite? (this can cause a hypertensive crisis)

Monoamine oxide inhibitors - an anti-depressant that binds to MO enzyme Marmite Monoamine

General anaesthetics and anti-depressants act centrally. What type of drug have you studied that acts peripherally?

Local anaesthetic

What do anti-depressants cause in brain activity?

Excitation

What does general anaesthetic cause in brain activity?

Depression

What can nervous system drugs do to ion channels?

Open or close them

What do muscle blockers do in surgery?

Relax muscles