Analgesics and Anti-emetics Flashcards
What is acute/ nociceptive pain ?
- short term pain
- easily identifiable cause
- warning of present damage to tissue or disease which responds well to medication
What is chronic or neuropathic pain?
- pain which persists
- constant or intermittent
- outlived its purpose since it no longer helps the body to prevent further injury
what is allodynia in reference to pain?
pain from a stimulus that does not normally cause pain
What is parasthesis?
painful feelings (eg pins and needles) with no apparent stimulus
Where do anti-inflammatorys normally act?
upon the relay station of the afferent pain impulse,
up the CNS.
- this intensifies the signalling process
opioids, serotonin (5HT) and norepinephrine/ noradrenaline act naturally to …
suppress inhibitory pathways
- drugs can enhance this pathway
What two ways can we reduce pain?
- prevent transmission of information upwards towards CNS (opioids)
- enhance inhibitory pathway
- anti - inflammatory’s too
There are three broad types of pain relief (not including anti-inflammatory) they include:
- opioids
- anti-depressants & antiepileptic’s
- local anaesthetics
What are the key things of each of these?
OPIOIDS
- modify the transmission of pain signals and the subjective perception of pain
ANTIDEPRESSANTS & ANTI-EPILEPTICS
- trigeminal neuralgia (pain with nerve in shoulder and jaw)
- neuropathic pain which is resistant to opioids
LOCAL ANAESTHETICS
- particularly effect for severe intractable or crescendo neuropathic pain
- associated with trauma
What is the mechanism of action for opioids?
- block pain pathway
- within CNS, with spinal cord
- decrease the transmitters that mediate pain pathway
- activate inhibitory pathways / MIMIC OUR ENDOGENOUS LIGANDS (ENKEPHALINS)
What are the unwanted side effects of opioids?
- will interact with medications and alcohol
- nausea and vomiting
- constipation
- drowsiness
- respiratory depression
- hypotension
- sedation
- dependency
What are the targets for anti-emetics and where do they act?
Dopamine
Substance P/ neurokinin NK
Serotonin/ 5HT receptors
ALL ACT ON THE CHEMORECEPTOR TRIGGER ZONE
serotonin/ 5HT
ACT ON VAGAL PATHWAY
histamine
muscarinic
ACT ON VESTIBULAR PATHWAY
muscarinic histamine antagonist 5HT3 substance P ACT ON VOMITING CENTRE
What are histamine antagonist used for?
motion sickness
vestibular diseases (affects the body balance)
GI irritants
What are examples of histamine antagonist used to treat motion sickness, vestibular disease and GI disturbance ?
CYCLIZINE - for motion sickness
CINNARIZINE - motion sickness, vestibular disease (vertigo and menieres disease)
PROMETHAZINE - severe morning sickness
Histamine antagonist are of limited use against substances that act directly on chemotherapy triggering zone. What are there other side effects?
drowsiness
sedation
What do muscarinic receptor antagonist treat in sickness? examples of this drug is hyoscine or scopolaimine
general use in sickness
motion sickness
What are the side effects of acetylcholine/ muscarinic receptor such as hyoscine or scopolaimine used to treat sickness?
dry mouth
blurred vision
less sedative than antihistamines
Dopamine receptor have strong representation in the chemoreceptor triggering zone and will also act on muscarinic and histamine and so has a more powerful anti-emetic response. what are they used to treat?
- uraemia
- Opioid induced emesis
- CINV
- GI disorders
- viral gastroenteritis
What are examples of dopamine receptors?
- phenothiazines
- perphenazine
- prochloropromazine
- metoclopramide
- domperidone
What are the side effects of dopamine receptor antagonist such as
- phenothiazines
- perphenazine
- prochloropromazine
- metoclopramide
- domperidone
sedative
hypotension
dystonia (muscle spasm and abnormal posture)
dyskinesia (abnormal or impairment of voluntary movement)
What dopamine mechanism of action?
receptors on chemoreceptor triggering zone
5HT/ serotonin antagonist are the choice of CINV (chemo sickness) and PONV (aesthetic sickness). What are the side effects?
GI disturbances
headaches
What are 5HT / serotonin antagonist used for?
chemotherapy sickness
aesthetic sickness
radiation induced vomiting
What is an example of 5HT/ serotonin antagonist?
ondansetron
Aprepitant is a neurokinin antagonist/ substance P. What are its side effects?
fatigue constipation/ diarrhoea loss of appetite hiccups dizziness ringing in ears anorexia headache
Aprepitant is a neurokinin antagonist/ substance P. What is it used to treat?
chemo sickness
aesthetic sickness
Neurokinin antagonist / substance P active in the late stage emesis with what drug?
cytotoxic
Cannabinoids are valuable in the treatment of CINV and thought to act via which receptors?
via opioid receptors in chemoreceptor triggering zone
agonist of the cannabinoid receptors
- also used for chronic pain management
Corticosteroids such as dexamethasone can act as anti-emetics. what is it effective against?
- vomiting caused by cytotoxins
Corticosteroids such as dexamethasone can act as anti-emetics. What are they used in combination with ?
dopamine receptors
5HT/ serotonin
as this improves actions
What drug would you give for morning sickness?
Promethazine (histamine receptor antagonist)
phenothiazine (dopamine receptor antagonist)
What drug would you give for motion sickness?
hyoscine (muscarinic antagonist)
promethazine (histamine antagonist )
cyclizine (histamine antagonist)
What drugs would you used to treat PONV?
phenothiazine (dopamine receptor antagonist)
metoclopramide (dopamine receptor antagonist)
What drugs would you used to treat CINV?
ondansetron (serotonin receptor antagonist )
phenothiazines (dopamine receptors antagonist)
What drugs would you use to treat sickness related to opioids?
haloperidol metoclopramide (dopamine receptor antagonist )
What drugs would you used to treat sickness related to gastroenteritis?
metoclopramide (dopamine receptor antagonist)
What drugs would you for anticipatory emesis?
benzodiazepines
Most opioids are U-receptor agonist. what do these act on?
- CNS
- spinal cord
- GI tract
- peripheral sensory neurones
How do antidepressants work in stopping pain?
Serotonin and noradrenaline mediate descending inhibition of ascending pain pathways in the brain and spinal cord
What types of pain are antidepressants that act on serotonin and noradrenalin are they effective against?
- neuropathic pain
- appear to work well in the disease environment such as diabetes or HIV related neuropathy
What are examples of antidepressants that work on inhibition of serotonin and noradrenalin ?
- citalopram
- paroxetine
^^^ serotonin - venlafaxine
- duloxetine
^^noradrenalin
how do SNRI/ SSRI work?
prevent the recycling of neurotransmitters & enhance the signal
What are the side effects of the SNRI such as venlafaxine and duloxetine?
venlafaxine
- prescribed for diabetic neuropathy
- nausea, sedation, headache and dizziness
duloxetine
- prescribed for peripheral neuropathy particularly in diabetic neuropathy
- nausea, somnolence, insomnia, dizziness
*they both interact with a lot of drugs
how do anti-epileptic drugs work in preventing pain?
- inhibit of voltage gated sodium and calcium
- inhibit glutamate and GABA
- inhibit action potential firing
- prevent impulse transmission
- limit neuronal excitation
- enhance neuronal inhibition
What are examples of anti-epileptic drugs and what kind of pain do they help with?
CARBAMAZEPINE
- glossopharyngeal neuralgia
- post herpetic neuralgia
- trigeminal neuralgia
- diabetic neuropathy
GABAPENTIN
- various neuropathy states
What are the side effects of carbamazepine?
- dizziness
- diplopia
- drowsiness
- fatigue
- nausea
- hepatotoxicity
- renal impairment
- tremor
skin reaction
caution with hepatic/renal impairment and cardiac disease
What are the side effects of gabapentin?
*current drug of choice due to limited side effects
- anorexia
-dyspepsia
- tremor
caution with :
- elderly
- renal impairments
- diabetes
- pregnancy
How do local anaesthetics work?
- inhibit of voltage gated sodium
- prevent nerve to nerve cell communication
- inhibit firing
- prevent impulse transmission
What are examples of local anaesthetics and their specific actions?
Lidocaine (xylocaine)
- blocks sodium channels
- effective in non cancer patients
Ketamine (ketalar)
- blocker of glutamate receptors (NMSA subtype)
How are lidocaine and ketamine administered ?
- lidocaine = IV
- Ketamine - is injectable but not favoured due to side effects
What are the side effects of lidocaine ?
- CNS effects (confusion)
- respiratory depression
- convulsions
- hypotension
- bradycardia
caution with:epilepsy, hepatic and respiratory impairments, AF, heart failure
What are the side effects of ketamine ?
- hypertension
- tachycardia
- tremor
- diplopia (double vision)
- myocardial depression
Caution with : hypertension, angina, heart failure, aneurysms, cerebral trauma and psychotic disorders
