Analgesic agents Flashcards

1
Q

what is the WHO ladder for analgesia?

A

3 step ladder to guide pain management
step 1 - paracetamol, ibuprofen
step 2 - weak opioids, codeine, tramadol
step 3 - strong opioids, morphine, fentanyl

adjuncts can be used along the way - steroids

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2
Q

what are the limitations of the WHO pain ladder?

A

doesnt account for type of injury e.g. chronic pain problem works for but if someone comes in with broken leg likely to need to start at step 3

doesnt account for neuropathic pain, ketamine or magnesium

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3
Q

Give a hollistic approach to how pain can be managed…

A

pain is complex can be managed via non pharm and pharmacological approaches.

non pharm - CBT, accupunture
pharm - either direct analgesics or other e.g. PPI or antidepressants
surgical - steroid injections, coeliac plexus block

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4
Q

how does management of visceral pain compare to neuropathic..

A

visceral - poorly localised, dull pain, potentially referred.
Opiates work well here. Or can consider the cause e.g. buscopan.

neuropathic - opioids dont work so well here.
gabapentin, pregabalin and amitryptilline are used.
capsascin cream - down reg VR1 receptors (substance P). baclofen for muscle spasms

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5
Q

what is the importance of perioperative analgesia?

A

Better patient experience

Prevention of other issues - early mobilisations, deeper breathing, reduced risk of pneumonias, less N&V, better nutrition and wound healing.

less stress response - risk of MI

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6
Q

what is meant by multimodel analgesia?

A

targetting pain from different receptors / modes of action
e.g. opioids, regional anaesthesia, paracetamol, ketamine.

means less of one drug has to be used so better side effect profile. opiate sparring

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7
Q

why might pre-emptive analgesia be useful?

A

better patient experience
less likely to develop chronic pain
easier to stop pain before it develops

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8
Q

which analgesic agents can work topically?

A

ibuprofen gel
fentanyl and buprenorphine patches - lipid soluble
local anaesthetic creams - EMLA or Ametop
capsaicin cream - initially burning sensation then down reg of VR1 receptors

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9
Q

which neurotransmitters affect descending pain pathways?

A

opioids - u receptor on SG
ketamine - NMDA receptor at SG
NA/5HT3 e.g. SSRIs and SNRIs , tramadol
reduces noradreanaline - clonidine

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10
Q

what atypical NSAIDs do you know?

A

paracetamol, aspirin

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11
Q

Tell me about the pathogenesis of paracetamol overdose

A

paracetamol can be metabolised by phase 1 and phase 2 metabolism within the liver.
In phase 1 - NAPQI is produced which is a toxic metabolite which is quickly conjugated with glutathione.
In phase 2 - paracetamol is glucuronidated - under normal conditions most is metabolised this way.

In OD - phase 2 becomes saturated and phase 1 metabolism increases, meaning more NAPQI produced. Glutathione stores also deplete and hence NAPQI can have toxic effects…

it causes centrolobular necrosis and can lead to fulminant hepatitis.

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12
Q

what factors contribute to depletion of glutathione and put patients at risk of paracetamol toxicity?

A

malnutrition - low BMI, starvation, malabsorption
genetic polymorphism
extremes of ages

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13
Q

At what level does paracetamol start to cause hepatic injury?

A

more than 150mg/kg

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14
Q

how does paracetamol OD present

A

N&V
RUQ pain
dearranged LFTs
after 72 hours - fulminant hepatitis and multiorgan failure

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15
Q

how is paracetamol overdose managed?

A

A to E, blood inc toxicology
accurate history
within 1 hour - activated charcoal

after than give N - acetylcysteine if - >150mg/kg, staggered overdose, acute liver injury, RUQ and jaundice with signs of liver failure.

otherwise take paracetamol level and use nonagram to decide to give NAC.

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16
Q

what is the dose for N-acetylcysteine?

A

150mg/kg in 1st hour
50mg /kg over 4 hours
100mg/kg over 16 hours

however now SNAP regime is used - 2 bags
100mg/kg in first 2 hours
200mg/kg in next 10 hours

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17
Q

what is the paracetamol nonagram?

A

guides need for NAC given levels of paracetamol post insult

not accurate under 4 hours or after 24hrs
no accurate if there is a staggeted overdose

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18
Q

how does N acetylcysteine work?

A

stimulates glutathione production
binds NAPQI and promotes its conjugation to non toxic products
reduces NAPQI back to paracetamol

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19
Q

any alternatives to NAC?

A

methionine

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20
Q

what are the ADRs of NAC?

A

rash, angioedema, flushing , N&V
can result in bronchospasm and low BP
SNAP regime has less incidence of this than classic 3 bag regime

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21
Q

how can the NSAIDs be classified?

A

Typical and atypical
Selective and non selective COX inhibitors

Typical:
* selective COX2 inhibitors = celecoxib and parecoxib
* non-selective = ibuprofen, ketorolac

atyptical
* aspirin - irreversible COX2 inhibitor
* paracetamol - Cox3 inhibitor

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22
Q

outline the pathway for prostaglandin production and how NSAIDs work..

A
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23
Q

tell me about COX enzymes

A

Cycloxygenase enzymes are a group of enzymes responsible for production of prostaglandins

different isoforms exist
COX 1 - found in most cells - particularly GIT, kidneys and platelets. responsible for GI protection, renal blood flow regulation and thromboxane synthesis in platelets

COX 2 - found in immune cells - responsible for prostaglandin production involved in pain and inflammation.

COX 3 - only in CNS - varient of COX 1, pyrexia and interpretation of pain in the brain.

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24
Q

why do NSAIDs exacerbate asthma?

A

block COX enzymes, build up of arachidonic acid which promotes leukotriene production via lipooxygenase

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25
what role do prostaglandins have in the body
gastric protection - increase blood flow and mucus production to protect epithelium from acid vasodilation - regulation of blood flow e.g. in kidneys platelet aggregation - thromboxone and hence homeostasis uterine contraction in maternity
26
what is reyes syndrome?
a rare life threatening condition associated with NSAIDs in children. particularly aspirin therefore aspirin contraindicated in under 16yrs unless kawasaki disease or juvenile arthritis results in encephalopathy, cerebral oedema, mitochondrial failure, hepatic failure.
27
describe the metabolic derrangements seen in aspirin overdose..
mixed respiratory alkalosis + metabolic acidosis aspirin stimulates resp centre - hyperventilation - resp alkalosis - drives HCO3 excretion which can worsen the acidosis... also causes uncoupling of oxidative phosphorylation - metabolic acidosis the acidosis results in increase in unionised form which means more can cross BBB. therefore better to be alkalotic as less toxic. hence sodium bicarb often given in overdose
28
what is role of sodium bicarb in aspirin OD?
alkalinsation of urine and blood urine - ion trapping, more aspirin excreted plasma - ionised form cant cross BBB and have toxic effects. can also achieve this through hyperventilation if mechanically ventialtion
29
what are the contraindications to NSAIDs use?
allergy - anaphylaxis or other GI ulceration / bleed renal impairment bleeding risk - caution if on warfarin under 16yrs caution in critically ill - AKI and stress ulcers. Asthma - relative - 10% of asthmatics have an issue pregnancy - aspirin can be used but mostly avoided due to premature duct closure. avoid in CKD, HF
30
what are the indications for NSAIDs use?
pain and inflammation pyrexia indomethicin in neonates to help close PDA
31
what are the pharmacodynamics of NSAIDs..
respiratory - bronchospasm - hyperventilation cardiovascular * risk of MI - esp COX2 specific GI: * ulceration and bleeding renal * AKI risk / reduced blood flow haem * bleeding risk neuro * reyes
32
how are the NSAIDs classified by their relative effect on GI bleeding risk?
high risk - ketorolac medium - naproxen, diclofenac low risk - ibuprofen COX 2 selective - even lower
33
what is the benefit of parecoxib / celexocib and risks?
selective for COX2 so target inflammatory effects of prostaglandins more hence less GI ulceration risk however found to be associated with thrombosis and MI
34
do you know any DDIs of NSAIDs...
highly protein bound and therefore displacement of others e.g. warfarin and phenytoin - bleeding risk SSRIs - risk of bleeding increased, ACEi - risk of AKI increased.
35
describe in general the pharmacokinetics of NSAIDs..
A: Oral, IV, gel, PR. weak organic acids - at stomach pH unionised so can be absorbed, but mostly duodenem due to high S.A mostly high BO. some 1st pass metabolism D: highly PB - albumin, low Vd M + E : hepatic and renal
36
are NSAIDS contraindicated in neuroaxial blocks?
no
37
what is the difference between an opiate and opiod?
opiate is naturally ocurring opioid e.g. morphine, codeine opioids are any molecule that can bind and act on opioid receptors - diamorphine, fentanyl, remifentanil, oxycodone etc - these include synthetic opiouds too.
38
what are endogenous opioids?
peptides produced in the body and act as neurotransmitters / neuromodulators at the opioid receptors. mostly found in PAG, hypothalamus, substantia gelatinosa classed into 3 groups endorphins - analgesia and euphoria - u and d receptors enkephalins - analgesia - d and u dynorphins - kappa receptor - analgesia, appeptite and circadian rhythms
39
describe the mechanism of an opioid receptor..
GPCR Gi found pre synaptically results in less cAMP, PKA hyperpolarisation via K+ efflux reduced Ca via VG Ca Channels. overall reduced transmission of pain signals
40
what opioid receptors do you know
4 classes mu, delta, kappa and nociceptin opioid receptor. also known as MOP, DOP, KOP and NOP. various subtypes of each found in PAG, NTS, thalamus, cortex, spinal cord, peripheral nerve terminals and some internal organs, MOP, DOP And KOP are classical receptors and anatagonised by naloxone NOP is non classical and not affected by naloxone
41
what are the specific roles of MOP, KOP, DOP and NOP.
MOP - found in brain, spinal cord and GI plexus - analgesia, euphoria, resp dep, constipation, spasm of spinchter of oddi, N&V , bradycardia. KOP - brain and spinal cord- analgesia and euphoria, increases ADH. also resp dep DOP - brain only - analgesia NOP - brain and spinal - anxiolysis, learning
42
endogenous opioids receptor ligands...
MOP - B endorphin KOP - Dynorphin A DOP - enkephalins NOP - nociceptin
43
what are the indications for opioid use?
pain - particularly visceral pain EoL - breathlessness, anxiety and pain antitussive antidiarrhoea remi - TIVA adjunct to propofol
44
which opioid is better in somoen with PONV?
alfentanil - wears off quickly so less likely to have post op effects oxycodone more favourable side effect profile than morphine.
45
how do PCAs work?
patient controlled analgesia button to press by patient that delivers a bolus 1-2mg of morphine, 5min lock out time. may also have background infusion running helps to match analgesia delviery with need and reduce delays for better outcomes. needs close observation - obs, pain score, record of total dose and needs to be seen by pain team once a day
46
what is tolerance and dependance?
tolerance - repeated exposure to a drug results in reduced response compared to previously. could be due to downregulation of receptors or uncoupling of intracellular pathways. larger dose needed for same effect dependance - physical symptoms of withdrawal in absence of drug. person has become dependant on the drug - may be psychological or physiological
47
what are the effects of opioid withdrawal?
pain anxiety feeling cold sweating discomfort - abdo cramps
48
how is an opioid dependant person managed perioperatively?
awareness of need for extra opioids can use adjuncts e.g. ketamine, paracetamol, regional techniques to reduce the need. continue methadone programme
49
what is methadone?
synthetic opiod used for addiction of opioids full agonist at u receptor and also NMDA antagonist longer half life than morphine and less sedating helps relieve withdrawal but has fewer euphoric symptoms so less addictive.
50
10mg of oral morphine is equivalent to how much oral codeine, dihydrocodeine, tramadol and oxycodone ?
oral codeine / tramadol/ dihydrocodeine = 100mg oxycodone = 6.6mg
51
how much morphine equivalnet is a fentanyl 25mcg/hr patch and buprenorphine 5mcg/hr patch?
fent 25mcg/hr = 60mg oral morphine in 24 hours buprenorphine 5mcg/hr = 12 mg morphine in 24 hours
52
what is 10mg of morphine equivalent to for IV diamorphine and morphine
IV/SC morphine = 5mg IV/SC diamorphine = 3.3mg
53
why does alfentanil have a faster action than a fentanyl
all opioids are weak bases they ionise below their PKA values. fentanyl pKA = 8.4 alfentanil PKA = 6.5 at physiological pH therefore using henderson hasselbach equation... fentanyl is 9:1 ionised / unionised alfentanil is 1:9 ionised / unionised therefore much more of alfentanil can cross BBB and exert effects. - much steeper gradient PLUS alfentanil is less potent so more of the drug can be used to create a steeper conc gradient. PLUS alfentanil is less lipid soluble than fentanyl so has a smaller Vd and therefore doesnt spread into lipid compartments
54
tell me about dihydrocodeine..
synthetic derivative of codeine more potent and not as dependant on CYP2D6 so less genetic variability
55
what is pethidine?
also known as meperidine synthetic phenyl piperidine U receptor agonisms but also NA/5HT3 reuptake inhibitor + anticholinergic effects + LA effects often used in obstetrics pharmacodynamics - analgesia - but also anti-cholinergic effects - dry mouth, urine retention, tachycardia - risk of serotonin syndrome - hypertension - risk of hypertensive crisis with MAOi cautions - readily crosses the placenta - more lipid sol than morphine - active metabolite - norpethdine - can cause convulsions (may accumulate in fetus)
56
tell me about naloxone?
u receptor competitive antagonist (aldo kappa and delta) used for reversin opioid intoxication comes in clear colourless solution for IV use given as 0.1mg - 2mg (titrated to effect) caution - shorter half life than morphine so may need infusion/ repeat dose
57
what are the side effects of naloxone?
pulmonary oedema flushing, headaches HTN and arrhythmias pain - withdrawal symptoms
58
do you know any partial opioid antagonists? what are the benefits of these?
buprenorphine, nalorphine can help with opioid dependance
59
compare the elimination of remifentanil and fentanyl?
both very lipid soluble however differ in metabolism - fentanyl hepatic, remi is unique in that it is metabolised by tissue and plasma esterases so remi is rapidly hydrolysed and thus effective Vd appears small very quick offset and context insensitive half life after 10mins fentanyl can accumulate in tissues due to its large Vd and hence although its clearance is 13 ml/kg/ hr, its half life is 2 hours. It has a context insensitive half time which increases rapidly with length of infusion
60
how do opioids affect the pain pathway?
peripherally - block peripheral receptors for nerve transmission ascending pathways - presynaptic - prevent transmission at substantia gelatinosa descending - in PAG - inhibit release of GABA which results in descending inhibtion
61
tell me about oxycodone
synthetic opioid full MOP agonist like morphine but better side effect profile food in elderly and better in renal disease
62
other than naloxone, do you know any other opioid antagonists?
naltrexone
63
what other receptors can opioids affect?
mast cells - histamine release tramadol and pethidine - NA/5HT3 receptor antagonist pethidine - anticholinergic effects
64
how is opoid withdrawal managed?
methadone benzos supportive care
65
how does acute opioid intoxication present?
opioids can cause respiratory depression and miosis often present with low GCS, low RR, pin point pupils other complication - hypothermia, long lie and rhabdo, risk of I.E, difficult access, malnourished
66
compare the clearance of opoiods medications and offset of action..
this depends on both their clearance and Vd clearance of * morphine = 16ml/kg/hr * fentanyl =13ml/kg/hr * alfentanil = 6 ml/kg/hr so would appear that morphine has quickest offset however half lifes... morphine = 170mins fentanyl = 190mins alfentanil = 100min this is because fentanyl is very lipid soluble so althrough clearance is more than double alfentanil, its half life is double. Vd morphine 3.5, fentanyl 4.0, alfentanil only 0.6 L/kg t1/2 = (Vd x 0.693) / Clearance
67
can remifentanil be used in labour?
PCA remi could be used in labour as pain releif - as short term and because rapidly metabolised, doesnt effect fetus some safety concerns because potent so could cause resp depression - would need monitoring
68
what other receptors does paracetamol act on ?
COX 3 inhibiton 5HT3 action
69
what is wooden chest syndrome?
complication of potent opioids, may be seen at induction... difficult to ventilate cant be reversed by naloxone but can be by NMBA
70
tell me about gabapentin..
GABA analgoue but doesnt act on GABA receptors.. works via VG Ca channels blockade in CNS - releasing NT also increases GABA via GAD can be used in epilepsy but now more commonly used in pain. side effects - weight gain, nausea , headaches
71
tell me about the role of pregabalin in pain?
agent for neuropathic pain belongs to pro-convulsant drugs blocks VG Ca channels in CNS reducing transmission of pain. (glutamate and substance P release) also increases GABA via GAD
72
what is the role of clonidine in pain?
this acts centrally at pre-synaptic a2 receptor s blocks release of NA involved in descending inhibition of pain pathways can be given IV or neuraxially other effects include sedation and hypotension. dexametetomidine - similar but more selective for a2 and more potent.
73
what analgesic agents do you know..
classed by MoA NSAIDS - COX inhibition , mostly peripheral Paracetamol - COX 3 , 5HT3 opioids - U receptor , central and peripheral neuropathic agents - VG Ca Channels and pain transmission tramadol and pethidine - mixed actions - opioid, NA/5HT3 KEtamine - NMDA antagonist N20 - NMDA + opioid Mg - NMDA + ca antaogonism clonidine - NA, central local anaesthetic - peripheral actions. cannabinoids - cannabinoid receptors
74
tell me about morphine
naturally occuring opiate phenathrene derivative used commonly as analgesic and in palliative care comes in oral liquid and clear colourless solution for injection. dose 0.1mg/kg IV. oral 5-20mg 2 hourly. can also be given intrathecally and epiduraly modified release also availble. pharmacodynamics.. full agonist at MOP and KOP therefore analgesia, euphoria, anxiolysis other effects considered by system Resp - depression - low RR, reduces chemoreceptor sensitivity to CO2, chest wall rigidity, supresses laryngeal reflexes, reduces cough. Can result in bronchospasm with histamine release CVS - bradycardia, hypotension (histamine) CNS - analgesia, sedation, euphoria, anxiolysis, misosi (via stimulation of edinger westphal nucleus) GI - N&V , reduces peristalisis - constipation, contraction of spinchter of oddi endo - reduces ACTH, LH, FSH, increases ADH Pharmacokinetics... A: weak base, pKa 8.2. oral absorption from small intestine. BO - 30% . D: Vd 3.5L/kg, , 30% PB M: hepatic = morphine 3 glucuronide and M6G. M6G is more active and can accumulate in renal disease E: renal excretion.
75
how long does it take for morphine to act?
10mins after IV 30mins after oral
76
tell me about diamorphine..
diacetylated morphine - synthetic opiate used for pain, palliative care, breathlessness in pulmonary oedema, and also recreationally. comes as oral 10mg tablets and also as a powder for IV injection. given at 10mg IV more commonly seen intrathecally - 0.1-0.4mg epidural 3mg Prodrug which is metabolised to morphine by esterases in plasma and tissues. first to monoacetylmorphine which is a full u agonist and then to morphine. then acts in same way as morphine but more potent pharmacokinetics - A: oral BO 30%, IV. very lipid soluble and pKA 7.6 so more unionised at physiological pH - can rapidly cross BBB. - D: PB 40% - M - ester hydrolysis and then hepatic like morphine - E - renal
77
why is diamorphine given intrathecally over morphine
more lipid soluble that morphine so acts at target site quicker and shorter lasting. morphine can linger around - risk of resp depression
78
tell me about codeine..
naturally occuring opioid , phenathrene derivative acts as a prodrug which is metabolised into morphine. used as analgesic agent and antitussive efects and antidiarrhoreal comes as tablets, oral suspension and can be mixed with paracetamol/ ibuprofen. Not given IV usually dose of 30-60mg QDS mechanism + dynamics 1/10th metabolised by liver CYP2D6 to morphine which then acts at u receptors therefore similar pharmacodynamics but less potent IV injection causes a lot of histamine release and hypotension so avoided. also has stronger anti-tussive effects pharmacokinetics A: well absorbed BO 50% D; v low PB, large Vd M: 10% to morphine via demethylation , 90% glucuronidation to norcodeine. subject to genetic polymorphism E: renal
79
what genetic polymorphisms is codeine subject to?
variation in CYP2D6 some will metabolise codeine very quickly - very sensitive to effects - hypotension, euphoria etc some will be slower metabolisers or not at all - no analgesic effects
80
Tell me about fentanyl..
phenylpiperdine derivative synthetic opioid used commonly for analgesia in hospitals, as induction agent and sometimes as infusion in ITU. also for chronic pain as transdermal patch comes as solution for IV injection - 50ug/ml in 2ml ampuoles. also comes as transdermal patch and as lozengers. At induction normally given 1-2ug/kg e.g. 100ug acts as a full u agonist pharmacodynamics - rapid onset within 2 mins, more potent than morphine and shorter duration - similar pharmacodynamics - less histamine release - because of potency more risk of bradycardia, apnoea and chest wall rigidity pharmacokinetics A- small intestine due to pKA 8.4 so ionised in stomach. extensive 1st pass metabolism. very lipid soluble to can cross BBB and can be absorbed across skin (lipid sol and small MW) D: Vd 4L/kg M: hepatic - inactive E: renal hence safe in renal failure.
81
tell me about alfentanil..
phenylpiperidine derivative, synthetic opioid used as fast acting analgesics and induction agent found in 2ml glass ampuloles as 500ug/ml. Usually 1mg given at induction. full u agonist structurally related to fentanyl however lower pKA - 6.5 making it much more unionised at physiological pH so much quicker onset of action (1-2mins) . not as lipid soluble as fentanyl so quicker offset. A: IV D: 0.6L/Kg - smaller vd than others , 90% PB M: liver - inactive metabolites E: renal, safe in renal failure
82
tell me about remifentanil..
synthetic opioid phenylpiperidine derivative main use in TIVA anaesthesia and for thyroid surgery where no NMBA can be used as it is a strong cough / resp depressant. OR in fibreoptic awake intubation. sedation in ITU for its very short CSHT. can also be used as bolus's in labour found as white powder for reconsituting with saline - 50ug/ml solution made. given as infusion 0.05ug-2ug /kg/min pure u full agonist pharmacodynamics - ultra fast onset and ultra fast acting. - very potent - similar to morphine - profound bradycardia -very good airway depressant - risk of hyperalgesia pharmacokinetics A: IV , pKA 7.1 - crosses BBB quick because more unionised. D: very lipid soluble but small Vd due to rapid metabolism M: ester hydrolsysi - non specific esterases in tissue and plasma - inactive metabolites t1/2 -5 mins short CSHT - after 6 mins - no change E - urinary - carboxylic acids
83
tell me about tramadol
synthetic opioid weak mu agonist + 5HT3/NA reuptake inhibitor effects * similar to morphine but less resp depression * less potent * others * risk of serotonin syndrome, hypertensive crisis (with SSRIs, MAOI) * lowers seizure threshold
84
tell me about buprenorphine...
partial agonist at MOP antagonist at KOP and DOP high affinity but low efficacy therefore in presence of morphine acts as an antagonsit as it competes with morphine for u receptors reducing effects of morphine however in absence of morphine gives some opioid effects to help with withdrawal can be given IV, oal , transdermal
85
what is nalbuphine?
agonist at KOP antagonist at MOP
86
tell me about paracetamol..
commonly used analgesic and antipyretic agent. classed as an atypical NSAIDs comes as oral or IV most commonly but also suppository. can be mixed with codeine and other meds e..g caffeine dose of 1g QDS in adults of normal BMI in children 15mg/kg it works via inhibition of COX3 reducing prostaglandin production in brain - hence analgesic and antipyretic effects. also activates descending serotonin pathways which helps with analgesic effects pharmacodynamics mostly seen when given IV e.g. hypotension, bradycardia can cause hepatotoxicity esp in OD Pharmacokinetics - A oral / IV - good absorption, BO 80% - D - small Vd, Pb 10% - M - hepatic - phase 1 (NAPQI) and phase 2 (glucuronisation and sulphation). under nromal circumstances 90% phase 2 - renal excretion.
87
tell me about aspirin..
salicylic acid, classed as atypical NSAID, for irreversible COX inhibition. used for pain, pyrexia, inflammation, antiplatelet effects (primary and secondary prevent of cardiovascular disease) oral tablet - 75mg, 300mg. also as a suppository works via non-selective irreversible cox inhibition resulting in reduced prostaglandins and thromboxane. hence reduced pain , inflammation and platelet aggregation. pharmacodynamics antiplatelet effects last 7 days due to needing to produce new platelets - resp - hyperventilation (CNS effect) - resp alkalosis , bronchospasm - GI - ulceration and bleeding - renal - risk of AKI - metabolic - uncouples oxidative phos - metabolic acidosis - haem - bleeding risk - CVS - fluid retention - not good for HF pharmacokinetics - A: prodrug , good oral absorption from stomach and small intestine. weak acid pKA 3.5, BO 80% - D: 85% PB, small Vd - M: hepatic and intestinal esterases metabolism to active form. then liver metabolism. shows 0 order kinetics quickly as liver pathways become saturated - E: renal excretion
88
what are the features of aspirin toxicity?
usually mixed resp alk and met acidosis pic with high anion gap CNS - tinnitus, blurred vision , may lead to seizures CVS - increased HR, low BP GI - N&V resp - hyperventilation, resp alk glucose derrangements
89
how is aspirin toxicity managed?
A to E good HX if within 1 hr - activated charcoal avoid intubation unless hypoventilation - as hyperventilation can help create alkalosis to reduce toxic effects correct electrolyte issues and glucose sodium bicarb can help to alkalinise blood and urine. haemodialysis
90
tell me about ibuprofen..
propionic acid derivative non selective NSAID commonly used for pain, inflammation and pyrexia oral tablets 200mg or oral suspension and as a topical gel 400mg QDS adults, 10mg/kg children reversible COX inhibitor - reduces prostaglandins dor pain and antipyrexia and anti-inflam. more favourable side effect profile to other NSAID
91
do you know any selective COX2 inhibtors , tell me about these...
celecoxib, parecoxib fewer side effects- GI and renal and bleeding however MI and thrombotic events contraindicated in IHD and stroke
92
tell me about diclofenac..
phenylacetic acid derivative non -selective reversible COX inhibitor used as analgesic agent, particularly good PR for renal stones. 50mg/100mg supossitory oral, suppository, injection and topical gel more potent but more side effects than ibuprofen
93
tell me about ketorolac
acetic acid derivative tablet or IV 30mg IV as slow bolus more potent and worse bleeding side effects