Pharmacology (not done) Flashcards
What is the MOA of lidocaine/pramoxine?
Sodium channel antagonist –> interferes with impulse production and action potential in nerves
What is the MOA of capsaicin?
TRPV1 agonist on C nerve fibers –> depolarization and neural desensitization
What is the MOA of topical menthol?
TRPM8 antagonist –> cooling sensation (no major benefits in dogs to date)
What is the MOA of antihistamines?
H1 receptor antagonists –> competitively block formation of histamine-receptor complex
What is the MOA of maropitant for itch?
Neurokinin-1 receptor inhibitor
What is the MOA of lokivetmab?
Anti-canine IL-31 mAB –> binds to circulating IL-31 and prevents it binding to its receptor
What is the MOA of ranevetmab?
Anti-canine nerve growth factor mAB (fails to prevent atopic itch)
What is the MOA of gabapentin and pregabalin?
GABA analog (inhibitory neurotransmitter) –> inhibits voltage-gated Ca channels in spinal cord –> reduces central neural hypersensitization
What is the MOA of topiramate?
NMDA receptor antagonist –> increases GABA activity and inhibits glutamate activity –> less neuronal excitability
What is the antipruritic MOA of butorphanol?
Mixed kappa-opioid agonist and mu-opioid antagonist
Would naloxone be potentially antipruritic?
Yes because it is a mu-opioid antagonist
What is the antipruritic MOA of amantadine?
NMDA receptor antagonist –> less neuronal excitability
What is the MOA of amitriptyline?
Tricyclic SSRI –> inhibits reuptake of serotonin –> increased neural impulses
What is the MOA of clomipramine?
Tricyclic SSRI –> inhibits reuptake of serotonin
(potent SSRI but not very specific)
What is the MOA of fluoxetine?
Bicyclic SSRI–> inhibits reuptake of serotonin
(very selective)
What is the MOA of doxepin?
SNRI –> inhibits reuptake of serotonin and norepi –> increased neurotransmission
Also has potent anti-H1 receptor properties
What is the MOA of mirtazapine?
SNRI –> antagonizes serotonergic and noradrenergic receptors
(useful for nocturnal pruritus)
How does vitamin E help in treatment of SNP?
Reduces damage from lipid peroxidation
What drug has been associated with a drug-induced panniculitis?
KBr
What is the MOA of itraconazole?
inhibits 14alpha demethylase –> prevents conversion of lanosterol to ergosterol
At which pH is oral itraconazole best absorbed?
Acidic (so giving with food helps)
What cutaneous adverse effect has been associated with itraconazole in dogs?
Vasculitis/ulcers (>10 mg/kg dose)
What is the MOA of ketoconazole?
Inhibits lanosterol 14alpha demethylase –> ergosterol depletion, accumulation of toxic sterols in the cell membrane
Which antifungal interferes with endogenous steroid synthesis?
Ketoconazole
What azole does not require food for optimal absorption?
Fluconazole
Which oral antifungal medication has the highest MIC (and thus the least efficacy) against dermatophytes?
Fluconazole
What is the MOA of terbinafine?
reversibly inhibits squalene epoxidase –> prevents conversion of lanosterol to cholesterol/ergosterol
Does terbinafine affect cytochrome P450?
No
What oral antifungal has the lowest MIC against Microsporum sp. and Trichophyton spp?
Terbinafine
What is the MOA of griseofulvin?
Arrests metaphase –> inhibition of nucleic acid synthesis and cell mitosis
Interferes with spindle microtubules
What is a potential side effect of griseofulvin in cats?
Bone marrow suppression (idiosyncratic)
What is the MOA of lufenuron for dermatophytosis?
disrupts chitin synthesis (this drug is NOT recommended for tx)
What are the primary side effects of meglumine antimoniate?
Cellulitis/abscesses at injection site
Nephrotoxicity
What is the MOA of allopurinol for tx of Leishmania?
Hypothanine compound –> metabolized by Leishmania and produces an inosine analogue –> analogue incorporated into Leishmania RNA –> faulty protein translation and inhibition of multiplication
How should allopurinol be administered?
Orally with a low purine diet
How does marbofloxacin help with treatment of Leishmania?
Increases production of NO by macs –> increased kill
Stimulates TNF-a production
When should TT4 be assessed for a patient on once-daily dosing of thyroid supplement?
Pre-pill/at time med is due (>1.5 mcg/dL is adequate)
What medication is FDA-approved for treatment of Cushing’s disease?
Trilostane
You have a dog on unequal doses of trilostane BID. After which dose should an ACTH stim be done for dose monitoring?
3-5 hr after the higher dose is given
How long should glucocorticoids be withdrawn prior to an ACTH stim or LDDST?
Oral/otic/opthalmic short-acting: 2 weeks
long acting: 4 weeks
At what time of day should a blood sample be collected when monitoring a hyperthyroid cat on methimazole?
Any time of day (does not matter when the med was given)
What is the effect of food on absorption of levothyroxine?
Reduces absorption (best given on empty stomach)
What is the MOA of methimazole?
Inhibits thyroid peroxidase
What are the main SE of lomustine?
Myelotoxicity
What is the MOA of doxorubicin?
Antitumor antibiotic that inhibits topoisomerase II
What is the MOA of imiquimod?
Activation of TLR7 –> secretion of IFN-a, TNF-a, IL-6
Activation of Langerhans cells
Activation of macs, NK cells, B-cells
What type of cells are targeted by palmitoylethanolamide (PEA)?
Mast cells
What is the MOA of PEA?
Mast cell stabilizer
What causes PEA to be released by the body?
Stress and tissue damage
True or false: skin levels of PEA are higher in healthy dogs compared to atopic dogs
False - they are 30-fold higher in atopic dogs
What is the active ingredient in Redonyl Ultra?
Ultra-micronized palmitoylethanolamide (PEA)
Are glucocorticoids lipophilic or non-lipophilic?
Lipophilic
Where are glucocorticoid receptors located?
In the cell cytoplasm
What occurs after a glucocorticoid binds to its receptor in the cytoplasm?
It translocates into the nucleus via importins
What does a ligand-bound glucocorticoid receptor bind to within the cell nucleus to reduce inflammation?
Glucocorticoid response elements (+GREs)
What genes are produced once a +GRE is bound by a ligand-bound glucocorticoid receptor?
Annexin-A1 (ANAX1)/lipocortin 1
GC-induced leucine zipper (GLIZ)
Mitogen-activated protein kinase phosphatase 1 (MPK1)
Besides directly interacting with DNA, how else can glucocorticoid receptors affect gene transcription?
Tethering: interaction with transcription factors themselves
What family of proteins is synthesized when a ligand-bound glucocorticoid receptor binds to DNA?
IkBs
How to IkBs affect inflammation?
They inhibit NF-kB, a major transcription activator for inflammation
How do glucocorticoids affect NF-kB?
They increase the amount of IkBs, which inhibit NF-kB activity
What 2 DNA sequences can ligand-bound glucocorticoid receptors bind to?
+GREs
nGREs
How do glucocorticoids affect leukotriene synthesis?
They enhance lipocortin production –> inhibits PLA2 –> interrupts arachidonic acid metabolism –> less leukotriene synthesis
What type of T-cells are primarily inhibited by glucocorticoids?
Th1
What cytokines are reduced by glucocorticoids?
IL-1
IL-6
IL-8
IL-12
TNF-a
IFN-gamma
(Th1 cytokines)
What cytokines are upregulated by glucocorticoids?
IL-4
IL-10
IL-13
What transcription factor is upregulated by glucocorticoids and what cell type is subsequently upregulated?
FoxP3
Treg cells
In which species do glucocorticoids not have any effect on neutrophil phagocytosis?
Horses
Goats
How do glucocorticoids reduce acute inflammation?
Prevent vasodilation and prevent increased vascular permeability
Which glucocorticoids have less sodium retention activity?
Prednisone/prednisolone
methylprednisolone
Which glucocorticoid has a high degree of sodium retention activity?
Hydrocortisone
What enzyme converts prednisone to prednisolone and where does this occur?
11-beta-hydroxysteroid dehydrogenase type 1
Liver
A dog with hepatic disease requires glucocorticoids. You have a choice between prednisone and prednisolone - which should be chosen?
Prednisolone (liver is responsible for conversion of prednisone to prednisolone)
Why are cats less responsive to typical steroid doses?
They have fewer glucocorticoid receptors in the liver and skin and receptors have lower affinity
What medication is derived from the fungus Beauveria nivea/Tolypocladium inflatum?
Cyclosporine
What class of drugs is cyclosporine?
Calcineurin inhibitor
What transcription factor is dephosphorylated by calcineurin?
Nuclear factor of activated T-cells (NFAT)
What is the MOA of cyclosporine?
Binds to cyclophilin intracellularly (within T-cells) –> this complex binds to calcineurin and inhibits its dephosphorylating activity –> prevents translocation of NFAT into the cell nucleus –> suppressed cytokine production and impaired T-cell activation
What cytokines are upregulated by NFAT activity in the nucleus?
IL-2
IL-4
TNF-a
TNF-gamma
True or false: It is acceptable to use compounded cyclosporine formulations in dogs.
False
What enzyme metabolizes cyclosporine and where does this occur?
CYP3A family (CYP3A4, CYB3B5)
occurs in liver
What mutation in dogs would warrant you to be cautious of CsA dosing as typical dosing could cause excessive immunosuppression?
MDR1
Why is cyclosporine a potential concern in patients with an MDR1 mutation?
It is a substrate of the p-glycoprotein efflux pump–> can accumulate if pump is defective due to MDR1 mutation (reduced biliary excretion)
What would the expected response to typical CsA doses be in a dog with diabetes?
Less response to typical dose due to increased clearance/reduced half-life
How long is it “safe” to store Atopica capsules in the freezer at -20 degC?
1 month
What type of drug is azathioprine?
pro-drug of 6-mercaptopurine (6-MP)
Which metabolites of azathioprine have no immunosuppressive effect?
6-thiouric acid
6-merthymecaptopurine (6-MMP)
What metabolite of azathioprine has cytotoxic/immunosuppressive effects?
6-thioguanine nucleotide (6-TGN)
What are the 3 metabolites of azathioprine?
6-thioguanine nucleotide (immunosuppressant)
6-thiouric acid (not immunosuppressant)
6-merthymecaptopurine (not immunosuppressive)
In what parts of the body does azathioprine conversion to 6-mercaptopurine occur?
RBCs
Intestinal wall
Liver
Which enzymes result in conversion of 6-MP to inactive metabolites?
Xanthine oxidase
Thiopurine-S-methyltransferase (TMPT)
Which enzyme results in the conversion of 6-MP into a cytotoxic metabolite?
Hypoxanthine-guanine phosphoribosyl-transferase (HPRT)
Which enzyme converts 6-mercaptopurine into 6-merthymecaptopurine?
Thiopurine-S-methyltransferase (TPMT)
Which enzyme converts 6-mercaptopurine into 6-thiouric acid?
xanthine oxidase
What enzyme converts 6-mercaptopurine into 6-thioguanine nucleotide?
hypoxanthine-guanine phosphoribosyl-transferase (HPRT)
How does azathioprine affect DNA synthesis?
It’s active metabolite (6-TGN) acts as a false purine –> incorporated into DNA –> mutated DNA, cell cycle stops
What cells are most affected by azathioprine?
Actively dividing cells (T-cells, B-cells, thrombocytes)
How does azathioprine affect leukocyte adhesion to endothelium?
6-MP inhibits RAC1 which is important for formation of ICAM-1 and VCAM-1
How does azathioprine affect T-cell migration, adhesion, and proliferation?
Inhibits RAC1 and BCL-XL
Responses from which T-cell subset are primarily blocked by CsA?
CD4+ (T-helper)
How long after dosing does oral CsA reach peak blood levels?
2 hours
Why should allopurinol be avoided when using azathioprine?
It inhibits xanthine oxidase –> causes more production of the cytotoxic metabolite of AZA (6-TGN)
What drugs should be avoided when using allopurinol for treatment of Leishmaniasis?
Anticoagulants
Azathioprine
Cyclophosphamide
Diuretics
TMS
Urinary acidifiers
Why should azathioprine be avoided in cats?
They are deficient in thiopurine-S-methyltransferase and therefore make less of the inactive metabolite and more of the cytotoxic metabolite –> increased risk of myelosuppression
What breed of dog is more susceptible to azathioprine toxicity and why?
Giant Schnauzers
They have less active thiopurine-S-methyltransferase activity, leading to more production of cytotoxic metabolites
What breed of dog may require higher doses of azathioprine and why?
Alaskan Malamutes
They have higher thiopurine-S-methyltransferase activity and therefore make more inactive metabolites
Combining azathioprine with which other immunosuppressant can cause an increased risk of pancreatitis?
Glucocorticoids