Block 8 Flashcards
Which anti-TB agent is able to inhibit membrane-bound ATP synthase and block ATP production in mycobacteria?
Bedaquiline
Define the MOA of thiazide diuretics.
They affect the distal renal tubular mechanism of electrolyte absorption –> they reduce the amount of salt and wter in the body by reducing tubular reabsorption
How do polyene antifungal agents work?
They are membrane disruptors
- they are the broadest spectrum antifungals
- MOA: bind to ergosterol and form pores (making the membrane leaky); affinity for ergosterol > cholesterols
** the number of double bonds directly correlates with fungal toxicity and selectivity
Which NA inhibitor is a prodrug that is orally active? How is it activated to its active form and what is that active form?
Which one is given via inhalation?
Which one is given by IV?
Oseltamivir - orally active prodrug; cleaved by esterase to active drug (oseltamivir carboxylate)
Zanamivir - inhalation
Peramivir - IV
What are the primary and secondary insults associated with NSAIDs and gastric damage?
Primary - direct acid damage, an indirect contact effect, and a back diffusion of hydrogen ions
Secondary - inhibition of PG biosynthesis in the GIT, where PGs exert a cytoprotective effect (COX1 inhibition)
What is the purpose of the drug Kionex (polystyrene sulfonate)?
Identify its MOA.
Controls potassium levels
MOA - as the resin passes along the intestine or is retained in the colon after administration by an enema, the sodium ions on the molecule are partially released and replaced by potassium ions
What is a noticeable structural different between imidazoles and triazoles?
Triazoles have 3 nitrogens in a 5 member ring.
Imidazoles only have 2.
What is unique about triazole function when compared to imidazoles?
they exhibit more selective toxicity and are associated with fewer side effects
What is typically given alongside isoniazid? Why?
Vitamin B6 because INH is an antagonist of it; adding more vitamin B6 to the patient’s diet prevents the side effects associated with the antagonistic activity
identify the MOA of epinephrine.
adrenergic receptor agonist
acts on both alpha and beta receptors
- alpha activation causes vasoconstriction and decreases vascular permeability that occurs during anaphylaxis
Which two steps (enzymes) in ergosterol biosynthesis can be targeted?
1 - squalene epoxidase (it’s the last non-cyclic molecule in the synthesis pathway, so by inhibiting this enzyme with allylamine antifungals we can inhibit the first step in producing ergosterol)
2 - P450 14-alpha demethylase (CYP51) (lanosterol is eventually converted to ergosterol by this enzyme, so azole antifungals will prevent synthesis in the final stages)
What are the two drugs that belong to the “aryl and heteroarylacetic acids” category of NSAIDs?
How do they differ?
Diclofenac - most widely used NSAID; is more potent than aspirin in anti-inflammatory and antipyretic properties; MOA is COX inhibition and reduced production of PGs along with inhibition of the lipoxygenase pathway and arachidonic acid release
Nabumetone - prodrug of 6MNA, which is an effective inhibitor of COX in joints; more active than aspirin at inflammation reduction bu 1/2 as potent in analgesic properties; pro - less gastric irritancy
Identify the drug and its MOA.
Montelukast (Singulair)
MOA - high affinity CysLT1 receptor binder, so it inhibits the activity of LTD4 at the receptor
What are important mechanisms to resistance to antifungal agents?
- target alterations
- reduced access to targets
Drugs for herpes are broken down into what 3 categories?
1 - Nucleoside Analogs
2 - Nucleotide Analogs
3 - Pyrophosphate Analogs
Describe the ideal qualities of an antifungal agent.
- broad spectrum activity against a variety of yeast and mold
- fungicidal rather than fungistatic (we want to kill it, not just stop it from dividing because immunocompromised people still won’t be able to kill it off themselves)
- selectivity for fungal vs. human cells
- multiple delivery methods (particularly oral availability) to enable prolonged out-patient care
- minimal side effects/toxicities
- essential to identify biological targets that are unique to fungi!
Core structures of nucleoside-guanosine analogs contain _____________ instead of ____________.
What is required for activity of this drug class? Why is this important?
Acyclic side chain instead of a ribose sugar
They have to undergo phosphorylation by a viral kinase for activity –> meaning this class is relatively nontoxic because they cannot be activated in uninfected host cells
The four types of asthma therapeutic agents are:
Adrenergic Agonists (alpha and beta)
Antimuscarinics
Adrenocorticoids
Leukotriene Modifiers
Match each drug with the appropriate description:
acyclovir, ganciclovir, foscarnet, cidofovir, oseltamivir, zanamivir
1 - this drug is administered by intravitreal injection to treat CMV retinitis
2 - a pyrophosphate analog which does not require activation by viral kinase
3 - an obligate DNA chain terminator
4 - is a nucleotide analog
5 - drugs of choice in ganciclovir resistant CMV as well as acyclovir resistant HSV
6 - orally effective prodrug used against flu virus
1 - Ganciclovir
2 - Foscarnet
3 - Acyclovir
4 - Cidofovir
5 - Foscarnet and Cidofovir
6 - Oseltamivir
How do corticosteroids reduce mucus secretion?
They inhibit the release of secretagogue from macrophages. They also inhibit the late phase reaction by inhibiting the inflammatory response and interfering with chemotaxis
How do PDE inhibitors help with COPD?
They increase cAMP and cGMP levels in cell types associated with release of inflammatory chemicals (such as T cells, B cells, monocytes, neutrophils, and eosinophils)
(COPD is associated with neutrophils)
What characteristics are needed for a good topical antihistamine?
- slow rate of receptor dissociation (long duration of action)
- logD ~1.0 +/- 0.5 at pH 7.4 (drugs with logD in this range are most efficacious and their water-soluble salts also show a low incidence of causing ocular irritation)
Give an example of a non-selective NSAID and its therapeutic benefits.
Salicylic Acid
Benefits: antipyretic, analgesic, and anti-inflammatory properties, promotes the excretion of uric acid (gouty arthritis); inhibits COX in platelet membranes, so irreversibly blocks formation of TXA2
Why can COX inhibitors be useful against fungi?
mPGES = microsomal PGE2 synthase (only in fungi)
COX inhibitors prevent the formation of PGE2, so COX inhibitors may reduce the activity that produces biofilms
Identify the drug. What are its proprietary names? Describe the MOA.
Hydroxyzine
Vistaril and Atarax
1st gen antihistamine
H1 receptor antagonist. (histamine allows fluid to escape from the capillaries into the tissues and this fluid is what is found with runny noses and water eyes during allergic reactions; histamine also induces swelling and the production of wheels in rashes)
What types of mutations are already being seen in response to antifungal agents?
Polyenes - resistance is rare and includes decreased ergosterol content in membranes
Azoles - low affinity to target enzyme (modified binding site, overexpression of enzyme, reduced accumulation of drug (efflux))
Allylamines - none detected, expected soon
Echinocandins - target mutation
5FC - inhibition of the transformation of 5-fluorocytosine to 5-florouracil
How can fungi become resistant to 5-FU?
they can block the reaction that cleaves 5-FU from its prodrug form to its active drug form.
What are the uses of foscarnet?
What is its MOA?
It is active against all types of herpes and HIV
- clinically used in ganciclovir resistant CMV and acyclovir resistant HSV
MOA: selective inhibitor of DNA polymerase (blocks pyrophosphate binding site)
__________ drugs prevent increases in cGMP levels, which are caused by interaction of ______ with the _______ receptors on bronchial smooth muscle.
Antimuscarinics
Acetylcholine
Muscarinic
__________ is a pyrofosphate analog
FOScarnet
The first NSAID to be marketed as a selective COX-2 inhibitor was ______. What other property needs to be taken into account when using this drug?
Celecoxib
It also inhibits CYP2D6, so it can affect the PK of other drugs (drug-drug interaction)
Identify the drugs.
Top - prednisolone
Middle - also prednisolone (putnam put it on this slide twice)
Bottom - fluticasone
Hydrocortisone looks like prednisolone, but the bottom left ring structure with the ketone does not possess two double bonds in hydrocortisone, it only has one.
Identify the drug. Which isomer is more active?
Naproxen
What is erythropoietin (EPO)?
- hormone produced by healthy kidneys that stimulates the bone marrow to make RBCs
(if your kidneys aren’t working properly, you won’t make enough EPO and you become anemic)
Which drugs are triazoles?
Fluconazole
Voriconazole
Itraconazole
Identify the drug and its MOA.
Benadryl (Diphenhydramine HCl)
1st gen antihistamine
H1 receptor antagonist; has anticholinergic (drying) and sedative effects (competes with histamine for H1 sites on effector cells)
Echinocandins are used to target _____________.
What limitations do they face?
Describe their MOA.
They target the cell wall and are used to treat resistant Candida and azole-resistant Aspergillus
limitations - need for daily IV administration because they have limited bioavailability and they are destroyed quickly
MOA: inhibition of the catalytic subunit of 1,3-beta-D-glucan synthase
Which drugs are members of the allylamine antifungal class?
Naftifine, Terbinifine, Butenafine, Tolnaftate thiocarbamate
Which drugs are classified as potassium-sparing diuretics?
Amiloride
Eplerenone (Inspra)
Spironolactone (Aldactone)
Triamterene (Dyrenium)
Identify the drug. Which isomer is more active?
Ibuprofen
S isomer
what’s the purpose of using antimuscarinics for asthma treatment?
Drugs that block the muscarinic fibers will cause cardiovascular, mydriatic, antispasmodic, antisecretory, and bronchodilatory effects
Describe the antibacterial activity of rifamycin antibiotics.
- broad spectrum (G+ and G- activity)
- bactericidal against intracellular and extracellular bacteria
- active aginst semi-dormant bacteria (sterilizing effect)
- resistance develops when used alone so is always used in combination with other agents
What is SRS-A?
SRS-A is slow-reacting substance of anaphylaxis.
- it’s a mixture of triene-containing lipids (LTC4, LTD4, and LTE4; all of which are cysteine-leukotrienes)
Which drugs are selective COX 2 inhibitors?
Celecoxib, Valdecoxib, and Meloxicam
Meloxicam was moved to the class for COX2 inhibitors
What properties do most 2nd gen antihistamines possess that prevent them from crossing the BBB?
- most are zwitterionic at physiological pH
and/or
- substrates for efflux (p-glycoprotein)
Ethanolamine Ethers belong to which generation of antihistamines?
1st generation
Describe the MOA and SAR of bedaquiline.
MOA: inhibits membrane-bound ATP synthase and blocks ATP production in mycobacteria
SAR: the tertiary amine, tertiary alcohol, ether oxygen, and bromine exert antibacterial activity by binding with amino acids of ATP synthase
In a culture positive for herpes simplex virus infection, parenteral therapy with acyclovir was started. The patient was at increased risk of develping what adverse side effect as a result?
Crystalluria
Identify the drug.
Nabumetone
Define the MOA of loop diuretics.
They inhibit sodium reabsprtion in the ascending loop of Henle. Reabsorption of chloride is also blcoked.
This causes the kidneys to get rid of more urine, lowering the amount of water in the body.
Describe the cell wall of Mycobacteria.
Thick, waxy cell wall that contains long chains of fatty acids called mycolic acid.
The mycolic acid is attached to the next cell wall component, a type of oligosaccharide called arabinogalactan
Identify the drug.
Amphotericin B
Why aren’t chitin and chitosan inhibitors used?
A common response to cell wall damage is strengthening of the cell wall by the production of excess chitin.
This mechanism is triggered when fungi are treated with echinocandin drugs.
Thus, enhanced chitin levels will then reduce susceptibility to echinocandin drugs
Because there are several ways to produce chitin, blocking one way will just result in excess production through the other way
What are the key points to remember about pyrazinamide?
- it’s a prodrug of nicotinamide
- it’s pH dependent and exhibits optimal activity under pH ~5
- is bactericidal against semi-dormant intracellular tubercle bacilli (sterilizing effect)
- decreases the pH and inhibits pH sensitive enzymes inside the cell
- prevents energy production
The most common Aspergillus mold species are…
A. fumigatus
A. niger
A. flavus
Allergy therapeutic agents are typically _________, which include…
H1 receptor antagonists
Ex. Diphenhydramine
Hydroxyzine
Cetirizine
Levocetirizine
Loratadine
Fexofenadine
What modification made the lead compound (in the development of zanamivir) selective for viral NA?
4-amino substitution
the 4-OH was replaced with a basic amine substitute.
It was then replaced with a guanidinium group (forms more H bonds and ionic bonds)
What may result from acute kidney failure? How can this be treated?
Acute kidney failure may result in too much fluid in the body, leading to swelling in the arms and legs. In these cases, medications (diuretics) may be used to expel extra fluids.
What are the two types of azoles? Why is there a risk of toxicity associated with these drugs?
Imidazoles and Triazoles
Azoles target CYP450, so many can also inhibit human CYP450 and cause toxicity
(Triazoles are more selective than Imidazoles)
Once isoniazid is activated, what is its specific MOA?
It forms an adduct with NAD, which then inhibits enoyl ACP reductase (InhA), a component of fatty acid synthase complex (FAS2) that helps make mycolic acid
Xyzal (generic name _______) is the active enantiomer of ________. Its principle effects are mediated via selective inhibition of ____________.
Levocetirizine
Cetirizine
H1 receptors
________ inhibits dCTP incorporation into viral DNA. Similar to guanosine analogs, it causes…
Why is the active form the diphosphate form?
Cidofovir
causes a slowing and subsequent cessation of viral DNA chain elongation
the active form is the diphosphate form because the phosphonate is not considered a phosphate (just a phosphate equivalent)
Compare acyclovir and ganciclovir in terms of spectrum coverage and clinical uses.
Acyclovir: HSVI > HSV2
*Note - HSV strains that are resistant to acyclovir are resistant to otehr guanosine analogs (cross resistance)
Ganciclovir: active againts CMV and most widely used in CMV infection (this is because phosphotransferase enzyme is the enzyme that works to activate ganciclovir, and it’s only found in CMV)
Identify the drug. What is it a metabolite of?
Cetirizine HCl (zyrtec)
It’s a metabolite of hydroxyzine