Heme/Onc Flashcards
Purine Degradation
-Purine -> Xanthine or hypoxanthine –> uric acid (xanthine oxidase)
Urate in the Kidney
- Urate is filter, secreted, and reabsorbed
- reabsorption predominates
- URAT-1 (OAT)
Causes of Hyperuricemia
- Under excretion due to renal impairment, HTN, low dose aspirin
- Urate overproduction from purine rich diet, tumor lysis syndrome
TX of asymptomatic Hyperuricemia
-Diet modification and weight loss
TX of symptomatic Hyperuricemia
- Diet modification
- Drug therapy to lower risks of recurrent attack, relieve symptoms of acute attack, and reduce serum urate levels
Drug Classes
- Uricostatic agents: reduce formation of uric acid
- Enzymes: metabolize uric acid
- Uricosuric Agents: Increase excretion of uric acid by the kidney
- Anti-inflammatory agents: relieve acute attacks of gout
Allopurinol
- Analog of hypoxanthine acts as competitive inhibitor of xanthine oxidase
- XO turns allopurinol into oxypurinol which is a non competitive XO inhibitor (longer half life)
- Dissolution of tophi by lowering serum levels of urate
- Decreases risk of nephropathy
- Increase risk of acute attacks due to tissue mobilization of urate (Colchicine given before therapy is started)
- Probenecid increases clearance of oxypurinol which requires incr. dose, but allopurinol increases the half life of probenecid requires lower dose
- Mercaptopurine and azathioprine require dose reduction due to inhibition of XO
- Hypersensitivity RXN (rash fever malaise and myalgias)
Feboxostat
- Non-purine, non-competitive inhibitor of oxidized and reduced form of XO
- Used as an alternative to allopurinol approved for hyperuricemia with gout attacks
- Abnormal liver functions, nausea, joint pain and rash
Pegloticase
- Urate oxidase that converts rate to inactive and soluble allantoin
- Peds tumor lysis syndrome in cases of leukemia, NOT CHRONIC GOUT
- pegylation increases half life and reduces antigenicity
- Blood samples for urate levels must be chilled to prevent enzymatic degradation
- Hemolytic anemia in G6P, anaphylaxis, metheglobinemia
Probenecid
- Decreases reabsorption of urate by inhibiting URAT-1
- Liberal H20 intake to prevent stones and keep urine pH above 6
- DONT USE: nephrolithiasis, over production of urate and patients with renal insufficiency
- Combine with Colchicine to prevent acute attacks
- GI irritation use caution with patients who have ulcers
- Salicylates reduce efficacy:
- Low dose blocks proximal tubule secretion of urate -> hyperuricemia
- High doses: block secretion and reabsorption w/ increase risk of stones
Losartan
-moderate uricosuric option for patients w/ HTN who are intolerant to probenecid
Anti-inflammatory Drugs
- NSAIDS: within 24 hrs of onset for 3-4 days and then taper for 7-10 (aspirin contraindicated)
- Glucocorticoids: Use if NSAIDs don’t work, intra articular administration effective if 1-2 joints affected
Colchicine
- Anti-inflammatory
- prevents activation, degranulation, and migration of neutrophils that mediate gout symptoms
- Enterohepatic recirc, dose reduction in liver and renal insufficiency
- Uses acute gout, and fixed dose combo with probenecid
- GI effects are frequent
- myelosuppression, leucopenia, granulocytopenia, thrombopenia, aplastic anemia
- Don’t use with 3A4 and P-glycoprotein inhibitors
- minimum of 3 days between treatments
Indomethacin
- nonselective COX-inhibitor
- 30-50% experience adverse effects
- GI effects can be fatal
- severe frontal headaches
- Seizures, depression, psychosis, hallucinations, and suicide
Amino Esters
Benzocaine cocaine Tetracain Procaine
Ester linkage between lipophilic and hydrophilic ends
Amino Amide
Lidocaine, Prilocaine, Meprivacine, Bupivacaine
-Amide linkage between lipophilic and hydrophilic ends
Mechanisms of action for local anesthetics
- Block Na channels along Axons when the channel is open in a voltage and time dependent manner.
- No loss of consciousness
- Reversible
- Ionized form has a higher affinity for the receptor
Local anesthetics crossing the membrane and blocking the receptor
-Non-ionized form diffuses across the nerve membranes while the ionized form (with H+ ion) blocks the receptor
Effects of Na+ blockage on nerve conduction
- Threshold for excitation increases
- Impulse conduction slows
- Action potential amplitude decreases
- Eventually ability to generate action potential is completely abolished
Fibers affected by Local anesthetics
- Local anesthetics are more efficacious on nerves that are rapidly firing or chronically depolarized
- C and B (pain)fibers are blocked first followed by A fibers
- A-alpha are blocked last (motor and proprioception)
- Recovery occurs in the reverse order
Potency and Duration of Local anesthetics
-Increases in lipophilicity –> increases in duration and potency.
Vasoconstrictors with Local Anesthetics
-Used to reduce rate of systemic absorption and prolong duration of action
Most potent and longest lasting amino ester
-Tetracaine (procaine shortest and weakest)
Most potent and longest lasting amino amide
-Bupivacaine (mepivacaine the worst)
Metabolism of Esters and amides
- Esters: Metabolized in plasma by plasma cholinesterases
- Amides: Metabolized in the liver by cytochrome P450 enzymes
Toxicity of local anesthetics
- Degradation: Hypersensitivity due to formation of benzoic acids and derivatives -> allergic rxns
- CNS: sedation, visual and auditory disturbances, tongue numbness and metallic taste, Nystagmus and muscular twitching –> tonic-clonic convulsions (depression of inhibitory pathways)
- Cardio: cardiac conduction and function effects (Bupivacaine)
Transient Nuerological Symptoms
-Syndrome of transient pain or dysethesia from spinal or epidural administration
General anesthesia
-Reversible CNS state loss of response to and perception of stimuli
Dissociative Sedation
-Trance like cataleptic state in which the patient experiences analgesia and amnesia but retains reflexes and CV stability
Inhalation
-Continuous inhalation of gas or volatile liquid which rate depth and duration of anesthesia are under control. Recovery occurs when gas is turned off and anesthetic is eliminated by exhalation
Intravenous
-Lipophilic and injected, rapid onset, but depth and duration are not well controlled, duration depends on rate of metabolism.
Stages of Anesthesia
- Conscious but drowsy with variable degrees of analgesia
- Excitement and delirum –> unconscious reflex response to pain (during recovery)
- Surgical anesthesia regular respiration
- medullary depression with loss of respiration and vasomotor control -> death
-Now defined as induction, maintenance and emergence
CV effects of general anesthesia
-Decrease mean arterial blood pressure by
vasodil, myo suppression, blunted baroreceptor reflex and decreased sympathetic tone
Respir effects of General anesthesia
- Reduced or eliminated vent. drive
- Lose gag and cough reflex
- reduced LES tone
Emergence
- Naseau and vomiting due to tim of CTZ (treat with 5HT3 agonist)
- Return of sympathetic tone –> Tachy and HTN
- Shivering treated with meperidine
Mechanism of Action
-Reversibly interact with hydrophobic sites of specific membrane receptors (enhance inhibit GABA)
Pharmacokinetics of Inhaled Anesthetics
-Achieve equilibrium between alveolar gas and brain tissue: exhaled gas = inhaled gas
which is affected by blood solubility, alveolar blood pressure and partial pressure
-Concentration is expressed as partial pressure (more H2O soluble = lower partial pressure)
-Blood solubility: Lower solubility = higher partial pressure = faster rate of induction
Nitrous Oxide
- Use in dental procedures or in combo to reduce dose of other inhalation agents
- Advantages: good analgesia and amnesia, minimal CV effects, Reduced side effects of other inhalation agents
- Disadvantages: Not complete anesthetic, rigidty, Diffusion hypoxia, Pneumothorax, inhibits b12 dependent enzymes so don’t use chronically
Halothane
- Induction/maintenance of anesthesia, still used in US for induction of peds (side effects less pungent)
- advantages: rapid induction and recovery, muscle relaxant/bronchodilator
- Disadvantages: Poor analgesic (hangover), significant cardiac depression (decrease MAP and sensitizes heart to epi tachy), Increase ICP, hepatitis
Isoflurane
- Use for maintenance at 1-2%
- Advanatages: good CV profile
- Disadvantages: pungent
Desflurane
Widely used for maintenance during outpatient due to fast onset and recovery
- Advantages: very rapid induction and emgerence, similar CV effects to isoflurane
- Disadvantages: Pungent -> bronchial irritation cough and salivation
Sevoflurane
- Wide use for induction and maintenance in kids
- Advantages: low pungency and good CV profile
Malignant hypothermia
- Genetically susceptible patients exposed to halogenated inhalation anesthetics and/or succinylcholine
- Post-op Hypercatabolic state: (hypercapnia, muscle rigidity, tachycardia, hyperthermia, hyperkalemia, Frequently fatal)
- Mutation in skeletal muscle dihydropyridine or ryanodine receptors -> excessive intracellular Ca accumulation (severe contractions)
- Tx: stop trigger, pure O2, skeletal muscle relaxant, and treat hyperkalemia and it’s related effects
IV anesthetics
- Used for induction
- Benzodiazepines used prior to sedation anxiolysis
- Given IV bolus or by constant infusion
- Barbituates: Methohexital, thiopental
- Non-Barbiturates: Propofol, Ketamine, etomidate
Methohexital:
- Short acting barbiturates
- Activates barbiturate binding site on GABA-A receptors
- Duration 10 min
- Induction of anesthesia and procedural sedation
Propofol
- Most commonly used IV agent in the US
- GABA-A agonist: sedative and amnestic, non analgesic
- Duration 6 min
- General anesthesia induction and maintenance
- procedural sedation
- Pst-Op anti emetic
- Hypotension, respiratory depression, pain at induction site, potential for hypertriglyceridemia (fosopropofol no side effects)
Ketamine
- NMDA receptro antagonist (blocks glutamate) -> dissociative sedation, significant analgesia and bronchodilation and minimal CV side effects
- Unpleasant emergence phenomenon, less prevalent in kids
- Can be used for procedural analgesia/sedation for brief painful procedures
- CNS pyschotomimetic: Vivid dreams, hallucinations, distorted visual and auditory sensitivity during emergence associated with fear and confusion, but may also produce euphoria can be counteracted with benzos
Causes of muscle spams
- Over stretching of muscle
- Repetitive strain of Muscle
- Wrenching of a joint
- Tearing of tendon or ligament
Spasm pain spasm
- Muscle overuse activates nociceptors in muscle which have synaptic connections with alpha and gamma motor neurons
- increased activity of neurons and increased muscle contraction
- Force of muscle contractions may compress blood vessels leading to ischemic contraction which excite nociceptors
Spasmolytics
- Chlorzoxazone, cyclobenzaprine, methocarbamol, orphenadrine
- All spasmolytic drugs alleviate the Sx of localized muscle spasms and no one is better than the other while all are equally effective as NSAIDS
- The difference amongst pain meds is onset and duration of action
Onset and duration of Spasmolytics
-Carisoprodol and methocarbamol are the quickest while cyclobenzaprine is the longest acting.
Mechanism of actions of the spasmolytics
- Depresses polysynaptic reflexes in the spinal cord (over monosynaptic)
- Cyclobenzaprine reduces tonic somatic motor activity influencing both alpha and gamma motor neurons
- Orphenadrine is an anticholinergic used to treat spasms of various etiologies ( i.e. lumbargo and sciatica
Cyclobenzaprine
- Related to tricyclics
- Serotonergic and noradrenergic
- Used for short term treatment of spasticity, not effective for treatment of spasticity
- Drowsiness, loss of coordination, anticholinergic, dizziness, physical dependence,
- At high doses: areflexia, flaccid paralysis, respiratory depression, tachycardia, hypotension
Methocarbamol
- Related to tricyclics
- Short term treatment of skeletal muscle spasms, but not effective for treatment of spasticity
- Drowsiness, loss of physical coordination, light headedness, dizziness, discoloration of urine
- After parenteral administration: syncope, hypotension, bradycardia, ataxia and vertigo, seizures, hemolysis
- Addicition and physical dependence
- CNS and respiratory depressions
Spasticity
- Increase in tonic stretch reflexes and flexor muscle spasms with muscle weakness
- Usually associated with brain or spinal cord injuries (loss of supra spinal inhibitory influence on alpha motor neurons
- Contractions are velocity dependent, greater resistance with faster stretches
Treatment of spasticity
- Reduce pain, frequency of spasms or irritating stimuli
- Improve gait, hygiene, and ADLs
- Multi-disciplinary approach
Baclofen
- Oral: Decrease spasticity due to multiple sclerosis and SC injury, can also be used for trigeminal neuralgia
- Intrathecal: Takes a lower dose and has fewer side effects. Used for Cerebral palsy, anoxic brain injury, MS, stroke, SC injury, AV malformation
- MOA: Binds presynaptic GABA B receptors which decreases Ca influx in presynaptic terminals which depresses the release of glutamate, aspartate, and reduces substance P release from nociceptive afferent nerve terminal
Depolarizing NMBD agents
- Agonists at nACh Receptors
- Depolarize end plates
- Produce fasciculations
Non-Depolarizing NMBD agents
- Competitive antagonists for nACh receptors, can also block pore of channel
- induce flaccid paralysis
- Do not depolarize end plate
- No fasciculation
NMDB structure
related to acetylcholine
Sensitivity to block by NMBDs
-Rapidly moving muscles > limbs > trunk> diaphragm
Succinylcholine
- Only brief relaxation required
- Rapid short action hydrolyzed by cholinesterase
- No crossing BBB
- Phase 1 Succinyl binds to nAChR and causes depolarization, not metabolized by ACh esterases leads to membrane remaining depolarized –> flaccid paralysis
- Phase II: Membrane may become repolarized but can’t be depolarized again (desensitized)
- BLOCKAGE CANT BE REVERSED BY ACh ESTERASE INHIBITORS
Succinylcholine metabolism
- Plasma cholinesterases hydrolyze in liver
- Only small fraction of drug reaches NMJ
- Block terminated by diffusion
- Side effects: Malignant hyperthermia, stimulate autonomic ganglia, hyperkalemia (release of K+) , myoglobinuria,
Blockage due to non-depolarizing blocker
-Can be reversed by ACh esterase inhibitor (edrophonium and neostigmine) allow ACh to build up and compete with NMDB
ND NMDB PK
- Dont cross BBB
- Rapid distribution followed by slower elimination
- Eliminated by plasma cholinesterases, excreted by kidney, metabolized by liver, spontaneous breakdown
Atracurium
- Slower onset of action with intermediate duration
- Organ-independent metabolism
- Laudanosine is a non-active metabolite (convulsions)
- Dose dependent histamine release
- Hemodynamic instability and bronchospasms
Cisatracurium
- Slow onset with intermediate duration
- Organ-independent metabolism
- Less laudanosine is produced (appropriate for infusion)
- Much less histamine is released compared to atracurium
Methotrexate: USES, Structure, and PK
- Used in early RA, RA w/ poor prognosis, generally first choice
- Orally or subq (bioavailability and fewer side effects) once/week (hepatoxicity) may take 4-6 weeks for effects
- Folic acid analog used for chemo, enter cells via folate transporter and is polyglutamated (traps and increases half-life)
Methotrexate: MOA
- Mech 1: inhibit purine synthesis by inhibiting dihydrofolate reductase and tetrahydrofolate formation (anti-cancer)
- Mech 2: Inhibits AICAR –> increase in adenosine –> resolution of inflammation (maybe major benefit in RA)
- Mech 3: Inhibits thymidylate synthetase –> reduction in thymidine levels –> inhibition of inflamm cell proliferation
Methotrexate: Side effects
- Rare hepatotoxicity with high doses, reason for once/week dosing, NO ETOH, Elevation of liver enzymes, Don’t use with liver failure
- NO RENAL INSUFFICIENCY
- NO PREGNANCY
- PULMONARY TOXICITY
- INCREASE INFX
- GIVE FOLATE 24 hrs. after administration to counteract side effects
Hydroxychloroquine
- Antimalaria drug thought to act by altering intracellular pH
- Orally effective with slow onset and LONG half-life
- Frequently used with MTX and/or sulfasalazine
- RETINAL DAMAGE (eye exams) more common with renal insufficiency
- hypoglycemia in diabetics (possible reduction in incidence of T2DM)
- Safe in pregnancy
- DONT USE WITH PSORIASIS OR PORPHYRIA
- Caution with neurological, hepatic, or hematologic disorders and alcoholism
Sulfasalazine
- Immune suppressive drug frequently used with hydroxycholorquine and MTX
- Orally effective –> salicylate and sulfapyridine (both poorly absorbed by affect GI immune system
- Skin reactions (urticaria, rash, and pruritus)
- Blood dycrasias in first 3-6 months
- Reduction in folate absorption so supplement
- DONT USE W/ SULFA or CELEBREX allergies
Triple Drug therapy
- Methotrexate weekly
- Try Hydroxychloroquine plus sulfasalazine daily
- try all three in combo
- Can add prednisone or NSAID
- Multiple drugs with synergist actions –> less side effects than any one drug by itself
- Goal: markedly slow or stop disease progression, ideally disease remission not just to relieve symptoms
Leflunomide
- Immunosuppressive agent which inhibits dihydro orotate (pyrimidine synth) and tyrosine kinase at higher doses.
- Inhibits T-Cell proliferation and reduces auto-antibody formation
- Orally daily –> teriflunomide (active agent)
- Extremely long half-life due to enterohepatic recirc.
- Cholestyramine to clear drug from body
- Inhibits CYP P450s
- Teratogenic and carcinogenic
- ABSOLUTELY CONTRAINDICATED DURING PREGNANCY need 2 negative tests two weeks apart
MInocycline
- Tetracycline antibiotic which inhibits metalloproteinases and collagenases
- Inhibits collagen degradation component of RA
- Effective one or twice daily in seropositive RA
- No real side effects
Biological response modifiers
- Peptides or proteins
- advances in making and suing peptides as drugs
- Target individual specific mediators early in inflame signaling cascade
- Start when tDMARDS fail as add on agent. More effective in combo with MTX
- Increased risk of info (TB, URI, herpes zoster, fungal)
- Blood dyscrasias
- Increased cancer incidence
ANTI-TNF
- Etanercept, Infliximab, Adalimumab
- Cytokine central to immune and inflammation, upstream regulator of many other immune/inflammatory cytokines
- Promotes inflammation and Joint destruction
Etanercept
- 2 Soluble p75 subunit of TNF receptor linked the the Fc domain of IgG1
- Binds TNF and prevents binding to cellular receptors inhibiting all steps down stream
- Protein, SC weekly, shortest duration
- Possible PML (rare viral infection of CNS
- Cancer risks similar to methotrexate
Infliximab
- Monoclonal antibody against TNF, not part of TNF receptor (mouse-human chimera)
- Administered IV 4-8 weeks always combined with MTX and other DMARDs
- Hypotension
Adalimumab
- Anti-TNF antibodies like infliximab (not part of TNF receptor just antibody against
- Fully humanized
- Injected SC every 2 weeks
- Approved for juvenile idiopathic arthritis
- Causes demyelination so contraindicated in patients with demyelinating disease like MS
CTLA-4, CD-80, and CD-28
CD-28 = T-Cell surface protein that recognizes activated APCS
CD-80 = on APCs is the CD-28 receptor
CD-80 and CD-28 binding activates the T-Cell
CTLA-4 is an antagonist for CD-80 that keeps CD-28 from binding there
Abatacept
- CTLA-4 Analog
- CD 28 receptor antagonist (binds CD-80)
- T-Cell activation inhibitor
- IgG1 and CTLA-4 binding domain fusion protein
- Injected SC weekly or IV monthly
- Severe RA not responsive to other DMARDS
- Serious INFX
- Infusion reactions (bronchospasm, angioedema, hypotension
- NOT COMBINED WITH TNF INHIBITORS (increased risk of INFX)
- NOT WITH PEOPLE WHO HAVE COPD
Rituximab
- Anti-CD20 monoclonal antibody and therefore and B cell inhibitor
- IV two injections two weeks apart
- Used w/ MTX
- Dont Use with anti-TNF
Concentration gradient and second gas effect
-Bulk uptake of one gas increases apparent concentration of second gas causing increase absorption of 2nd gas.
Elimination of Anesthetic
- Reverse process -> exhalation
- More blood soluble agent -> hangover
- Diffusion back in to the lungs can result in hypoxia b/c partial pressure increases -> decreased partial pressure of O2
- Currently used agents are only minimally metabolized b/c metabolites are toxic
Potency of inhalation anesthetics
- Minimum concentration of agent required to induce anesthesia
- MAC = minimum partial pressure that prevents movement in 50% of adult patients
- MAC ISN’T related to induction time.
Calcineurin Inhibitors (Cyclosporine): MOA
- Interferes with T-Cells by binding to cyclophilin to for a calcineurin inhibitory complex
- Calcineurin activates NFAT which leads to IL-2 transcription
- IL-2 activates T-Cells
Calcineurin Inhibitors (Cyclosporine): PK, and Therapeutic uses
-PK: Poor oral, CYP 3A4 (grapefruit juice), individual dosing and blood level monitoring
Uses: Prevent rejection of allogenic kidney, liver, lung, and heart, usually given with glucocorticoids
-DOESNT REVERSE ACUTE EPISODES OF ESTABLISHED REJECTION
-Psoriasis, and rheumatoid arthritis
-Dry eyes
Calcineurin Inhibitors (Cyclosporine): adverse effects
- CsA ISNT MYELOTOXIC!
- Nephrotoxicity: does dependent and reversible, reduction in RBF due to fibrosis
- HTN: renal vasoconstriction and Na retention
- Tremor, hirsutism, gingival hyperplasia
Calcineurin Inhibitors (Tacrolimus): MOA and Uses
-Similar to CsA (not in structure)
-Binds to FKBP-12 and forms a complex that inhibits calcineurin
-More potent and better efficacy than CsA
USES:
-Prevent rejection of kidney, liver, lung and heart with glucocorticoids
-Psoriasis and rheumatoid arth
-Topical for atopic dermatitis, and oral for ulcerative colitis
Calcineurin Inhibitors (Tacrolimus): PK and Adverse effects
- CYP3A4
- nephrotoxicity
- Neuro: seizures and tremors
- Hyperglycemia and diabetes
- HTN
mTOR Inhibitors (Sirolimus): MOA and Uses
MOA:
-Binds and complexes with FKBP-12 that then binds to and inhibits the MTOR complex 1
-MTOR complex 1 is a serine threonine kinase and inhibition arrests T-Cell division in G1 phase
USES:
-Kidney transplant rejection in combo with CsA B/C lower risk of kidney toxicity
-Steroid refractory acute and chronic GVHD
-CAD
mTOR Inhibitors (Sirolimus): PK and Adverse effects
PK: -60 hr T1/2 -CYP3A4 and P-glycoprotein elimination Adverse: -Profound myelosuppression -Poor wound healing -Incr. serum cholesterol and triglycerides (STATIN) -NOT FOR LIVER OR LUNG TRANSPLANT
Cytotoxic (Antiproliferative) Agents (Azathioprine): MOA, Uses, and Adverse effects
MOA: -Prodrug of 6-Mercaptopurine -Direct antiproliferative (s-phase) effects on activated T-cells and reduces B-Cell activation but less effects on antibody production USES: -Adjunct with other agents to prevent rejection -RA in NON-PREGNANT PATIENTS AE: -Myelosuppression -Mutagenic and teratogenic -Dose reduction w/ pts on Allopurinol
Cytotoxic (Antiproliferative) Agents (Mycophenolate Mofetil): MOA, Uses, AE, and PK
MOA:
-Prodrug of mycophenolate
-Highly specific for T and B lymphocytes due to heavy reliance on de novo pathway for purine synthesis
-Reversible non-comp inhibit of lymphocyte inosine monophosphate dehydrogenase
Uses:
-Heart, liver, kidney transplants,
Adverse effects:
-GI effects, myelosuppression, infections
PK:
-converted by plasma esterases to MPA
