Muscle Pain Pharm Flashcards
What are the most common analgesics for muscle pain?
NSAIDs & Paracetamol
What are 5 contraindications of NSAIDs?
1) Kidney impairment
2) Heart failure
3) GI ulcer/bleeding
4) Bleeding disorders
5) Systemic corticosteroids/ antiplatelet/ anticoagulations
6) 3rd trimester
How should NSAID choice be altered for a px at risk of renal toxicity?
AVOID all NSAIDs
- just maintain hydration and avoid hypovolemia
How should NSAID choice be altered for a px at risk of CVS toxicity?
Only celecoxib or ibuprofen
- limited to <6days
- if cannot NSAID → paracetamol alone
How should NSAID choice be altered for a px at risk of GI toxicity?
Avoid non-selective NSAIDs
- use COX2 selective w caution (eg. celecoxib)
- co-pharmacy with GI protectant (eg. PPI)
How should NSAID choice be altered for a px at risk of NSAID-related bronchospasm/pseudoallergic rxn?
Avoid non-selective NSAIDs
- use COX2 selective w caution (eg. celecoxib)
What is the triple whammy in NSAID pharmacology?
NSAID + Diuretics + ACEi → ↑↑↑AKI
NSAID inhibit COX → ↓prostaglandins → Afferent arteriole constriction → ↓renal blood flow
Diuretics → ↓blood volume
ACEi → prevent efferent arteriole contriction → cannot maintain glomerular BP
When should paracetamol be used in caution?
1) Hepatic dysfunction/alcohol abuse
2) Underweight/cachectic/frail
What is the main risk in paracetamol overdose?
Hepatotoxicity
Alternating paracetamol and ibuprofen improves _________ while combining them improves _____________.
Alternating → prolong antipyretic
Combined → ↑analgesia
True or false:
Paracetamol is commonly used to relief muscle pain via its anti-inflammatory effects.
False.
For anti-pyretic and analgesic
- NOT anti-inflammatory at clinical doses
What is the moa of tramadol?
1) Weak opioid
2) Serotonin-norepinephrine reuptake inhibitor (SNRI)
When is tramadol prescribed for muscle pain?
Moderate to severe pain in combination w NSAID or paracetamol
What are 2 AEs of tramadol?
1) Constipation, nausea, vomiting
2) Respiratory depression
3) Dependence
What is the most important principle when prescribing opioid analgesics to prevent dependency?
Use lowest effective dose of weakest effective opioid for shortest duration
- ensure px is well-educated on use, storage and risk of AEs
True or false:
Opioid combinations are often more effective than NSAIDs for pain associated with acute inflammation?
False.
NSAIDs are often more effective than Opioid combinations for pain associated with acute inflammation?
What are 4 AEs of opioid analgesics?
1) GI effects
2) Hormonal effects
3) Depression
4) Respiratory effects
5) OD and death
6) Falls and fractures
7) Sedation/drowsiness → accidents
8) Tolerance/dependency
9) Hyperalgesia
What are 4 risk factors for opioid analgesics?
1) CNS depressants (eg. alcohol, benzodiazepines, anti-depressants)
2) Comorbidities (eg. mental health conditions)
3) Renal insufficiency
4) Hepatic insufficiency
5) >65 y/o
6) Prenancy
7) FHx of substance use disorder
8) Other opioids
Of the muscle relaxants,
__________ is used for acute muscle pain while ______________ are reserved for subacute/chronic/refractory muscle and neuropathic pain.
Acute muscle pain → Orphenadrine
Subacute/chronic/refractory muscle and neuropathic pain → Benzodiazepines/GABA analogues
What is the moa of orphenadrine?
Central muscle relaxant:
1) Muscarinic receptor antagonist
- tertiary amine → crosses BBB well → muscarinic receptors in basal ganglia
2) H1 antihistamine
3) NMDA receptor antagonism
4) NE and Dopamine reuptake inhibitor
5) Na-channel blocker
What are 4 AEs of orphenadrine?
Common:
1) Nausea and vomiting
2) Flushing
3) Dilated pupils
4) Xerostomia
Higher doses:
5) Tachycardia
6) Ataxia
7) Nystagmus
8) Drowsiness
9) Delirium
10) Agitations
11) Visual hallucinations
When should orphenadrine be used with caution?
1) Other CNS sedatives
2) 1st gen antihistamines
3) Anticholinergics
4) Antiparkinsonian drugs
What is the moa of benzodiazepines (eg. diazepam)?
1) Allosteric modulators or GABAA receptors→ ↑freq. of Cl channel opening ↑potency of GABAnergic neurotransmission
2) Suppress brain reticular activating system
3) ↑inhibitory neurotransmission
What are 3 indications for benzodiazepines?
1) Muscle relaxant
2) Sedative/hypnotic
3) Anxiolytic
4) Anti-epileptic for status epilepticus
5) Induction of anaesthesia
What are 2 AEs of benzodiazepines?
1) Drowsiness/impaired judgement/↓motor skills
2) Tolerance and high potential for dependance
3) PD DDI with other CNS depressants
What is the moa of Baclofen?
CNS GABAB receptor specific GABA analogue → ↓tonic neural stimulation to muscles
What are 2 indications of baclofen?
1) Skeletal muscle spasms and/or pain
- usually in combination with NSAID or paracetamol
- should be used temporarily
2) Spasmolytic in px with MS or spinal cord lesions
What are 2 AEs of Baclofen?
1) Sedation, weakness, CNS effects
2) Withdrawal syndrome (with abrupt cessation)
- hyperthermia, pruritus, ↑spasticity
What is the moa of Gabapentinoids (eg. Gabapentin, pregabalin)?
GABA analogues but act at voltage-gated Ca channels → ↓tonic neural stimulation to muscles
What are 3 indication for Gabapentinoids (eg. Gabapentin, pregabalin)?
1) Neuropathic pain
2) Chronic pain refractory to other treatments
3) Anti-epileptic for partial seizures
What are 2 AEs of Gabapentinoids (eg. Gabapentin, pregabalin)?
1) Somnolence, dizziness, ataxia
2) Renal elimination w/o metabolites → heavily dependent on renal f(x)
What is the main indication for adjucts for muscle pain?
In combination with analgesic for subacute/chronic/refractory muscle and neuropathic pain
What is the moa of topiramate?
Reduces tonic neural stimulation to muscles by:
1) Inhibits excitatory neurotransmission
- block AMPA subtype glutamate receptors
- block voltage-sensitive Na channels
2) potentiate inhibitory GABAnergic neurotransmissioon
What are 2 indications for Topiramate?
1) Chronic neuropathic pain
2) Anti-epileptic for partial seizures and adjuvant for generalised tonic-clonic seizures
What are 2 AEs of Topiramate?
1) Dizziness, fatigue
2) Ataxia
3) Confusion
What is the moa of Duloxetine?
5-HT and NE reuptake inhibitor (SNRI) antidepressant
What are 2 indications of Duloxetine?
1) Chronic/neuropathic pain
- low back/non-radicular neck pain
2) Clinical depression
What are 3 AEs of Duloxetine?
Common:
1) Xerostomia
2) Abdo pain
3) Drowsiness
4) Fatigue
5) Headache
6) Weight loss
Severe:
7) Mania
8) Hypomania
9) Bleeding risk
10) Fragility fractures
11) Hepatoxicity
12) Hyponatremia
13) Ocular effects
14) Serotonin syndrome
15) Sexual dysfunction
16) Suicidal ideation
What is the moa of amitriptyline?
TCA antidepressant inhibits reuptake of NE and serotonin (5-HT)
What are 2 indications of amitriptyline?
1) Chronic/neuropathic pain
2) Clinical depression
What are 3 AEs of amitriptyline?
Antihistamine:
1) Sedation
2) Weight gain
Anticholinergic:
3) Blurred vision
4) Xerostomia
5) Urinary retention
6) Constipation
7) Agitation
8) Tachycardia
9) Sweating
α1 blockade:
10) postural hypotension
11) tachycardia
What are 3 analgesics used for myalgia?
1) Opioids (eg. tramadol)
2) Paracetamol
3) NSAIDs (eg. celecoxib)
What are 3 muscle relaxants used for myalgia?
1) Orphenadrine
2) Benzodiazepines (eg. diazepam)
3) GABA derivatives (eg. baclofen, gabapentin)
What are 3 adjuvants used for myalgia?
1) Anticonvulsants (eg. gabapentin, topiramate)
2) Antidepressants (eg. Duloxetine, amytriptiline)
