Pharmacology Flashcards
Describe the physiology of the RAAS?
- short and long term blood pressure regulation
- regulation of plasma volume
- modulation of sympathetic NS
- stimulates thirst
What is renin?
- proteolytic enzyme produced from the JG cells
- regulates the formation of Angiotensin II
What endogenous chemicals cause increases in angiotensinogen synthesis?
- insulin
- estrogens
- glucocorticoids
What is the relationship of renin and sodium intake?
- increases in sodium will cause decreases in renin release
How is renin secretion controlled?
- Intrarenal baroreceptor pathway - measures blood vol.
- Macula densa pathway - increase NaCl flux across MD decreases renin release
- Beta adrenergic receptor pathway - increases release
What are the feedback inhibition pathways?
- Ang II stimulates AT1 receptors on JG cells to decrease renin release
- Ang II increases BP which decreases renin release
What are the effects of Ang II?
- increases total peripheral resistance - direct vasoconstriction, sympathetic activation
- alters renal funciton - aldosterone release, constriction of renal arterioles, contraction of mesangial cells
- ## alters cardiovascular structure (via AT1 receptor activation)
What is the mechanism of action of ACE inhibitors?
- inhibits conversion of Ang I to Ang II
- inhibits degradation of bradykinin
What are the pharmacological effects of ACE inhibitors?
- increases release of renin (without effect)
- increases circulating Ang I
- decreases aldosterone release
- prevents/reverses remodeling of cardiovasculature
What are the pharmacokinetics of ACE inhibitors?
- cleared renally
What are the therapeutic uses of ACE inhibitors?
- hypertension
- congestive heart failure
- acute myocardial infaction
- high risk cardiovascular events
- diabetic nephropathy - reduces glomerular capillary pressure, delays disease progression
What are some adverse effects associated with ACE inhibitors?
- hypotension at first does
- cough
- angioedema
- hyperkalemia
- acute renal failure (w/ pre-existing bilateral renal arterial stenosis)
- never use in pregnant patients
- antacids reduce the bioavailability
- NSAIDS reduce efficacy
- NSAIDS, potassium sparing diuretics and potassium supplements can lead to hyperkalemia
What is the mechanism of action of ARBs?
- competitive antagonist of the AT1 receptor
- high affinity for the AT1 over the AT2
- inhibits aldosterone secretion
How are ARBs differing from ACE inhibitors?
- ARBs reduce AT1 receptor activation more effectively
- ARBs maintain the AT2 receptor beneficial effects from Ang II binding
- ARBs should have no effect on bradykinin
What are the therapeutic uses for ARBs?
- hypertension
- Reno-protective in type 2 DM
- congestive heart failure
What are the adverse effects associated with ARBs?
- slight cough and rare angioedema
- don’t give to pregnant patients
- hypotension and renal failure in pts w/ RAS-dependent BP (renal artery stenosis)
- hyperkalemia
What is the mechanism of action of direct renin inhibitors?
- block conversion of angiotensinogen to Ang I
- increase in renin in plasma due to no Ang II feedback
- no effect on bradykinin
What are the therapeutic uses of direct renin inhibitors?
- hypertension (alone or in combo)
What some adverse effects associated with direct renin inhibitors?
- slight cough and rare angioedema
- don’t give to pregnant patients
- hypotension and renal failure in pts w/ RAS-dependent BP (renal artery stenosis)
- hyperkalemia
What are the different drugs used to inhibit RAS function?
- Angiotensin Converting Enzyme Inhibitors (cptopril, enalapril and enalaprilat)
- Angiotensin Receptor Blockers (losartan)
- Direct Renin Inhibitors (aliskiren)
What are the different classes of diuretic drugs?
- Carbonic anhydrase inhibitors (acetazolamide)
- Na-K-2Cl symport inhibitors (furosemide)
- Na-Cl symport inhibitors (hydrochlorothiazide, chlorothiazide)
- K-sparing diuretics - ENaC inhibitors (amiloride, triamterene), Aldosterone antagonists (spironolactone, eplerenone)
- Osmotic diuretics (mannitol)
- Vasopressin receptor antagonists (demeclocycline, tolvaptan)
What are the functions of the kidneys?
- filter large quantities of plasma
- maintain blood volume
- maintain acid-base balance
What are the three components of the filter in the glomerular capillaries?
- fenestrated capillary
- basement membrane beneath the endothelial cells
- filtration slit diaphragms
What is solvent drag?
- solutes are flowing with filtered water
What are the characteristics of the proximal tubule?
- 65% reabsorption of filtered Na
- highly permeable to water
What are the characteristics of the Loop of Henle?
- Descending thin limb - highly permeable to water, low permeability to Na and urea
- Ascending thin limb - permeability to NaCl and urea but not water
- Ascending thick limb - actively reabsorbs NaCl and impermeable to water and urea
- 25% of filtered Na is reabsorbed
- Macula densa senses NaCl leaving the Loop
What is the significance of the Macula Densa?
- senses NaCl leaving the Loop of Henle
- when NaCl is high, constriction of the afferent arteriole of the nephron will occur
- constriction of the afferent arteriole will protect from salt and volume wasting
What are the characteristics of the distal convoluted tubule?
- actively transports NaCl
- impermeable to water
- “diluting segment of the nephron”
What are the characteristics of the collecting duct?
- fine adjustments in electrolyte composition are made
- modulation done by aldosterone and ADH (modulating water permeability)
What are the seven mechanisms by which Na may cross the renal epithelium?
- sovent drag
- simple diffusion
- channel-mediated diffusion
- carrier-mediated diffusion
- ATP mediated transport
- symporters
- antiporters
Describe renal handling of Cl?
- reabsorption follows reabsorption of Na
- occurs paracellularly in the proximal tubule and thick ascending limb of the Loop
- occurs transcellularly in the proximal tubule, thick ascending limb, DCT and collecting duct
- symport, antiport and Cl channels
Describe renal handling of K?
- 80-90% reabsorbed in proximal tubule by diffusion and solvent drag
- secreted in DCT and collecting duct (channel mediated)
Describe renal handling of Ca?
- 70% is reabsorbed by proximal tubule by passive diffusion
- 25% is reabsorbed by the thick ascending limb
- 5% is reabsorbed in DCT
Describe renal handling of phosphate?
- 80% reabsorbed by proximal tubule
Describe renal handling of Magnesium?
- mainly reabsorbed in the thick ascending limb by a paracellular pathway due to a potential difference
Describe renal role in acid-base balance?
- reabsorb HCO3 and secrete protons
- substances not bound to protein are filtered
- substances bound to proteins are actively transported into nephron
Why is it important to know medications effects on ion transporters in the nephron?
- drug-drug interactions can occur because multiple drugs use same transporter (either for clearance or to get to activation site)
- will decrease efficacy of drugs that must cross these transporters to get to site of activation (furosemide)
What are the main concepts of diuretic action?
- disruption of sodium conservation (increase water excretion)
- sodium transporters and channels are targets
- will modify renal handling of other ions as well
- the nephron will try and compensate by reabsorbing Na downstream (leads to loss of potassium)
What is the mechanism of action of the carbonic anhydrase inhibitors (CAIs)?
- competitive inhibitor of carbonic anhydrase both within the cells and on the apical membrane
- blocks formation of protons to be exchanged for the reabsorption of Na
What are the effects on the urinary electrolytes that are excreted?
- increase in Na excretion
- increase in K excretion due to compensation for the early loss of Na in the tubule
- increase in HCO3 = decrease in urinary pH
What is the effect of CAIs on the macula densa?
- increases NaCl passing the macula densa
- reducing GFR
What are the therapeutic effects of CAIs?
- open angle glaucoma
- altitude sickness
- Epilepsy
How does acetazolamide treat altitude sickness?
- makes the plasma more acidic which increases the breathing rate to try and bring back to homeostasis which will increase the amount of oxygen to the brain
What are the adverse effects of CAIs?
- hypokalemia - due to renal compensation
- urinary alkalization leading to renal stones, potassium wasting and worsen hepatic encephalopathy by diverting ammonia into systemic circulation
What is the mechanism of action of the Loop diuretics?
- inhibit the Na-K-Cl symporter
- removes the potential across the epithelial cell stopping Ca++ and Mg++ reabsorption
What are the effects of Loop diuretics on the urinary electrolytes being excreted?
- major increase in Na
- increase in K
- increase in Cl
- no change in HCO3 excretion
- increase in Ca++ and Mg++
How does a Loop diuretic effect renal blood flow?
- stimulation of renin release leads to increase of RBF (GFR)
How is a Loop diuretic delivered to its site of action?
- bound to proteins so it is not filtered
- passes through anionic transporters
What are the therapeutic uses for Loop diuretics?
- Acute pulmonary edema (increasing venous capacitance)
- Congestive heart failure (depleting volume)
- Hypercalcemia (removing gradient)
What are some adverse effects of Loop diuretics?
- hyponatremia and hypokalemia
- hypocalcemia
- ototoxicity - alteration in inner ear electrolytes
- hyperuricemia
- hyperglycemia
- NSAIDs will reduce efficacy
What is the mechanism of thiazides and thiazide-like diuretics?
- inhibition of the Na-Cl symporter
- weakly inhibits the carbonic anhydrase
What effect does thiazides have on urinary excretion of electrolytes?
- increase Na
- increase K - due to renal compensation
- increase Cl
- small increase in HCO3 - due to weak CAI
- decreases excretion of Ca++
How is a thiazide drug brought to its site of action?
- delivered via an anion transporter
What are the therapeutic uses of thiazides?
- Hypertension
- mild edema
- Nephrogenic diabetes insipidus
- Calcium nephrolithiasis and osteoporosis
What are some adverse effects of thiazides?
- hypokalemia, hyponatremia
- hyperuricemia
- hyperglycemia and hyperlipidemia
- erectile dysfunciton
- NSAIDs will reduce efficacy
What are two types of Potassium sparing diuretics?
- ENaC inhibitors (triamterene and amiloride)
- Aldosterone antagonists (spironolactone and eplerenone)
What are the mechanisms of action of ENaC inhibitors?
- block Na reabsorption by blocking the Na channels on the apical side of the cell
What are the mechanisms of action of Aldosterone antagonists?
- block cytosiolic mineralocorticoid receptors and reduces expression of the ENaC transporters
What are the therapeutic uses for potassium sparing diuretics?
- prevent hypokalemia
- Liddle syndrome and cystic fibrosis
- primary hyperaldosteronism, hepatic cirrhosis, CHF
What are some adverse effects associated with potassium sparing diuretics?
- hyperkalemia
- gynecomastia, impotence, hirsutism, dicreased libido
- metabolic acidosis
What is an example of an osmotic diuretic and where does it effect the nephron?
- mannitol
- entire nephron length
What is the mechanism of action of osmotic diuretics?
- increases the osmolality of tubular fluid
- reducing passive reabsorption of NaCl in ascending lip of the Loop
- inhibits the release of renin
How does mannitol effect urinary excretion and renal hemodynamics?
- increases all electrolytes being excreted
- increases RBF and maintains GFR
How is mannitol used therapeutically?
- minimize acute tubular necrosis
- reduces pre/post op CSF and intraocular pressure
What are some adverse effects associated with osmotic diuretics?
- contraindicated in heart failure and active cranial bleeding
- flash pulmonary edema
What are the effects of vasopressin (ADH)?
- vasoconstriciton with V1a stimulation
- increase Na and urea reabsorption transporters as well as the movement of aquaporins in the collecting duct (with V2)
- net result is increased water retention and concentration urine
What are some vasopressin receptor antagonists?
- demeclocycline
- tolvaptan
What is the mechanism of aciton of vasopressin receptor antagonists?
- competitive antagonists of the V2 receptors
- increase water excretion without change in electrolyte excretion
How is a vasopressin receptor antagonist used therapeutically?
- hyponatremia associated with SIADH
What adverse effects are associated with demeclocycline and tolvaptan?
- demeclocycline - all tetracycline side effects and diabetes insipidus
- tolvaptan - hyperglycemia
Losartan
- ARB
Aliskiren
- direct renin inhibitor
Captopril, Enalipril, Enaliprilat
- ACE inhibitor
Acetozolamide and Methazolamide
- Carbonic Anhydrase Inhibitors
Demeclocycline and Tolvaptan
- Vasopressin receptro antagonists
Furosemide
- Loop diuretic
Chlorothiazid and Chlorothiadone
- Na-Cl inhibitor
Triamterene and amiloride
- ENaC inhibitor
Spironolactone and eplerenone
- aldosterone antagonist
Mannitol
- osmotic diuretic
What are some drugs that are used as anti-influenza medications?
- amantadine
- oseltamivir
- zanamivir
What are some drugs that are used as anti-herpes medications?
- acyclovir
- valacyclovir
- ganciclovir
- valganciclovir
- cidofovir (with probenecid)
- foscarnet
What are some drugs that are used as anti-viral hepatitis medications?
- interferon alpha
- ribavirin
- simeprevir
- sofosbuvir
- entecavir
What are three general properties of antiviral drugs?
- often have higher host toxicity than antibiotics
- most are nucleosides, used to prevent replication of viral nucleic acids
- they are predominantly virustatic and host immune system clears the infection
What is the most effective approach to prevent influenza infection?
- vaccination
What is the mechanism of action of amantadine?
- blocks influenza A M2 ion channel
- interferes with viral uncoating
What are the pharmacokinetics of amantadine?
- orally available and well absorbed in GI
- eliminated renally
WHat are the therapeutic uses of amantadine?
- not currently recommended because of resistance
What are the adverse effects associated with amantadine?
- lowers the seizure threshold
- no use in pregnancy
- interacts with anticholinergics
What is the mechanism of action of oseltamivir?
- competitive inhibitor of neuraminidase
- interferes with spread by preventing release
What are the pharmacokinetics of oseltamivir?
- orally available
- metabolized in the liver
- excreted by the kidneys
What are the therapeutic effects of oseltamivir?
- prevention/treatment of influenza A and B
- must be given with 48 hours of symptom onset
What are the adverse reactions and degree of resistance for oseltamivir?
- slight nausea and bomiting
- variable resistance in seasonal flu
What are some characteristics of zanamivir?
- neuraminidase inhibitor
- low or bioavailability
- inhalation administration - can cause bronchospasms
What are the characteristics of HSV infection?
- genital warts
- infection in mouth
- miningitis
- encephalitis
What are the characteristics of VZV infection?
- chickenpox
- shingles
What are the characteristics of CMV?
- infects immunocompromised
- retinitis, lung and GI infection
What is the drug type of acyclovir?
- nucleoside analog for HSV and VZV
What is the mechanism of action of acyclovir?
- conversion by viral kinase into acyclo-GMP
- conversion of acyclo-GMP by host kinase into acyclo-GTP
- acyclo-GTP will cause chain termination by inhibiting viral DNA polymerase
How does resistance develop for acyclovir?
- viral kinase deficiency or mutation
What are the pharmacokinetics of acyclovir?
- orally effective with low bioavailability
- widely distributed and eliminated unchanged by kidneys
What are the characteristics of valacyclovir?
- it is a prodrug that increases the bioavailability
What are the therapeutic uses of acyclovir?
- HSV all infections
- VZV can lessen the infection time
- used for more severe cases
What are the adverse effects associated with acyclovir?
- neurotoxicity
- reversible renal dysfunction
What type of medication is ganciclovir?
- nucleoside analog for CMV
What is the mechanism of action of ganciclovir?
- converted by the viral kinase and then by host kinase and then inhibits viral DNA polymerase
What are the pharmacokinetics of ganciclovir?
- orally effective with low bioavailability
- eliminated unchanged in the kidneys
What are the characteristics of valganciclovir?
- increased oral bioavailability
What are the therapeutic uses of ganciclovir?
- restricted due to toxicity
- treats CMV retinitis
- prevention of CMV in transplant pts
What are the adverse effects associated with ganciclovir?
- myelosuppression (neutropenia, thrombocytopenia)
- CNS (fever, convulsions)
What type of drug is cidofovir?
- nucleotide analog for CMV
What is the mechanism of action of cidofovir?
- converted only by host kinase
- inhibits viral DNA polymerase
What are the pharmacokinetics of cidofovir?
- poor oral bioavailbility
- used with probenecid to increase efficacy
What is the therapeutic use of cidofovir?
- CMV retinitis in AIDS pts
What are the adverse effects associated with cidofovir?
- nephrotoxicity because of probenecid use
- neutropenia
- possible carcinogen
What type of drug is forcarnet?
- non-nucleoside analog for HSV and CMV
What is the mechanism of action of forcarnet?
- effective on all herpesviruses and HIV
- inhibits herpes DNA polymerase
- inhibits HIV reverse transcriptase
What are the pharmacokinetics of forcarnet?
- poor oral bioavailability
- most eliminated unchanged by the kidney
What is the therapeutic effect of forcarnet?
- only for drug resistant herpes viruses
What are the adverse effects associated with forcarnet?
- nephrotoxicity
- electrolyte disturbances (hypocalcemia)
What are some characteristics associated with HCV?
- considered curable because no genomic integration
- no vaccine
- major risk for hepatocellular carcinoma
What is the standard treatment for HCV?
- 24-48 week treatment with combination of interferon alpha and ribavirin
What is the mechanism of action of Ribavirin?
- broad spectrum against DNA and RNA viruses
- converted by host kinases
- depletes GTP pools within cells
- unknown causing lethal mutations in RNA viruses
What are the pharmacokinetics of Ribavirin?
- given orally or inhalation
- high Vd and long half life
- eleminated by hepatic metabolism and renal excretion
What are the therapeutic uses of Ribavirin?
- in fixed dose with INF alpha for HCV
- pediatric RSV brochiolitis and pneumonia
What are the adverse effects associated with Ribavirin?
- hemolytic anemia
- contraindicated during pregnancy
What is the mechanism of action of INF-alpha2a?
- not directly acting on viral proteins
- activates Jak-STAT signalling to increase immune response to stop viral replication
- stimulates MHC class I and II
What are the characteristics of pegylated INF-alpha2a?
- interferon attached to large polyethylene glycol
- increases the half life
What are the pharmacokinetics of INF-alpha2a?
- well absorbed in SC or IM injection
- pegylation increases serum concentration and prolongs duration
What are the therapeutic uses for INF-alpha2a?
- chronic HCV and HBV in combo with other drugs
- genital warts associated with HPV
- cancers - Kaposi’s, lymphomas, melanoma
What are some adverse effects associated with INF-alpha 2a?
- Flu-like syndrome
- Neuropsychiatric - depression
- Myelosuppression
What type of drug is simeprevir?
- direct acting antiviral for HCV
What is the mechanism of action of simeprevir?
- inhibits viral protease
- analogous to HIV protease inhibitors
What are the pharmacokinetics of simeprevir?
- given in combo with ribavirin/INF
- metabolized by CYP3A4
What are the adverse effects associated with simeprevir?
- photosensitivity and rash
- contraindicated in pregnancy
What type of drug is sofosbuvir?
- direct acting antiviral for HCV
What is the mechanism of action for sofosbuvir?
- nucleotide prodrug metabolized to inhibit viral RNA polymerase
What are the pharmacokinetics of sofosbuvir?
- in combo with ribavirin and INF
- efficacy across all HCV genotypes and low resistance
What are some characteristics of HBV?
- DNA virus that integrates into host genome
- vaccination available and effective
- therapy used for persistant elevated serum ALT and HBV DNA
What are the treatment options for HBV?
- Pegylated INF
- entecavir
- Tenofovir
- Lamivudine
What is the mechanism of action of Entecavir?
- converted by host cell kinase
- inhibits HBV DNA polymerase
What are the pharmacokinetics of entecavir?
- orally available
- excreted unchanged in urine
What are the therapeutic uses of entecavir?
- first line treatment for chronic HBV (administered for 1 year)
- not active against HIV
What are the adverse effects associated with entecavir?
- risk of lactic acidosis and hepatomegaly when fatty liver
What drugs are classified as nucleoside revers transcriptase inhibitors?
- zidovudine
- lamivudine
- emtricitabine
- tenofovir
What drugs are classified as non-nucleotide revers transcriptase inhibitors?
- efavirenz
- nevirapine
What drugs are classified as protease inhibitors?
- lopinavir/ritonavir
- atazanavir
What drugs are classified as integrase inhibitors?
- raltegravir
What drugs are classified as fusion inhibitors?
- enfuvirtide
- maraviroc
What are the goals for antiretroviral treatment?
- maximal suppression of plasma HIV RNA
- restoration and/or preservation of immune function
- limitation of drug adverse effects
- reduction in HIV-associated morbidity and mortality
What are the antiretroviral treatment guidlines?
- treatment recommended for all symptomatic and asymptomatic HIV infected patients
- a 3 drug regimine is the minimum standard of care
- therapeutic failure is an increase in viral load
- treatment failure requires initiation of a completely new regimen
What are some consequences of antiretroviral therapy?
- lifelong therapy
- HIV lipodystrophy syndrome
- complex pharmacokinetics with drug associations
- immune reconstitution inflammatory syndrome
What is IRIS?
- reversal of immunodeficiency in pts with low CD4 counts
- usually occurs in initial treatment phase
- usually due to opportunistic infection with an accelerated inflammatory reaction