Acute Pain & OFA pt2 Flashcards
Codeine metabolism is variable due to more than ____ polymorphisms resulting in analgesic variability.
50
What is the adult dose and max of codeine?
15 - 60 mg q4
360mg max per day
What is the pediatric dose and max of codeine?
0.5 - 1 mg/kg/dose
60mg max per day
should be avoided in children?
60mg of codeine (maximal dose) is equivalent to how much aspirin?
650mg
What drugs does codeine have interactions with? (3)
Opioids, EtOH, and Anticholinergics
What drug is described by the following?
Tramadol
Where does the + enantiomer of tramadol have affinity and what does it do? (3)
Centrally acting opioid agonist:
- μ → moderate affinity
- K & δ → weak affinity
- Opposes serotonin reuptake
What does the - entantiomer of tramadol do? (2)
- Inhibits NE reuptake
- Stimulates α2 receptors
What is tramadol metabolized into and what is the relevance of its metabolite?
Tramadol → CYP3A4 & 2D6 → O-desmethyltramadol (2-4 times more potent)
What is tramadol’s potency compared to morphine?
1/5 to 1/10
What is the oral onset for tramadol?
1-2 hours
What is the half life of tramadol?
6.3 hours
When is tramadol contraindicated? (2)
- Seizure Disorders
- PONV
What are the benefits of tramadol vs other opioids? (3)
- Minimal respiratory depression
- Minimal-none addiction
- Minimal constipation
Oral morphine dose is ____ times the IM or IV route.
3
What receptors are primary affected by morphine?
μ-1 and μ-2
What are the two principle active metabolites of morphine? (also list effects)
- Morphine-6-glucuronide → analgesia
- Morphine-3-glucuronide → neurotoxicity & hyperalgesia
How is morphine metabolized?
- Hepatic: conjugation w/ glucuronic acid
- Kidneys
What factors contribute to morphine’s minimal CNS absorption?
- ↓ lipid solubility
- ↑ protein binding
- ↑ Ionization at normal bodily pH
What is the IV/IM onset and peak of action for morphine?
Onset: 15-30 min
Peak: 45-90 min
What differences does morphine exhibit in women vs men?
In women:
↑ analgesic potency
↓ speed of offset
What is the protein binding of morphine?
What about the half-time?
35% protein binding
1.7 - 3.3 hours
What is released from morphine administration?
What is the result?
Histamine → vasodilation and hypotension
Morphine should be avoided in patients with ____ impairment as the metabolite morphine–6-glucuronide can accumulate and lead to _________ ________.
Renal impairment : respiratory depression
What drug is a semisynthetic derivative of thebaine and is the most used opioid worldwide?
Oxycodone
What are the metabolites of oxycodone?
Oxymorphone (active)
Noroxycodone (inactive)
Oxycodone is primarily a prodrug.
What is the site of action of oxycodone?
μ and κ receptors of the CNS
What are the two types of PO oxycodone?
IR = Immediate release
CR = Controlled release
What is the dose of oxycodone?
10 - 15mg (equivalence with 10 mg morphine)
What is the onset of action of oxycodone?
< 1 hour
Opioids (in general) exhibit an ____ effect with other drugs that are CNS depressants
additive
Why is methadone used for opioid addiction maintenance? (3)
- 60-95% oral bioavailability
- High potency
- Long duration of action
What should be known about methadone’s half life?
Very long and unpredictable (up to 36 hours)
Can accumulate w/ repeated doses
What various receptors affinities does methadone have? (4)
- Weak noncompetitive NMDA antagonist
- Serotonin reuptake inhibitor
- Monoamine reuptake inhibitor
- High μ receptor affinity
What would occur with concurrent methadone and carbamazepine use?
Carbamazepine is a CYP450 inducer thus methadone will be metabolized faster.
What agents can inhibit the metabolism of methadone?
CYP450 Inhibitors:
- Antiretrovirals
- Grapefruit juice
How much is methadone clearance affected by hepatic and renal impairment?
Not much
What is the dose of methadone?
2.5 - 10 mg PO/IM/SC q4-12 hours
Why are standardized simple dosing guidelines unachievable for methadone?
High variable half life (8-80 hours)
What is the worst med interaction associated with methadone?
MAOI’s
What drugs are known to increase the concentration/effects of methadone? (3)
- Cipro
- Diazepam
- Acute EtOH
What drugs are known to decrease concentration/effects of methadone? (5)
- Anti-retrovirals
- Phenobarbital
- Phenytoin
- Rifampin
- MAOI’s
What cardiac complication can occur in rare cases with methadone usage?
Pause dependent dysrhythmia
What is the half life of codeine?
3-3.5 hours