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GI final - drugs drugs drugs
n/a
152
Accounting
Pre-School
12/18/2009

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Term
virus specific drug tx is available for which acute hepatitis infections?
Definition
just HCV! A B D and E mostly centered around PREVENTION.
Term
HAV vaccine - how long is it effective and how many doses (when)?
Definition
lasts 20 years, give one shot (abs develop within 2-3 weeks) then booster 6-12 months later
Term
HAV vaccine made from what?
Definition
inactivated virus
Term
HBV vaccine made from what?
Definition
recombinantly engineered
Term
what is the dosing for the HBV vaccine?
Definition
3 IM injections - 0, 1, 6 months. (10-20mg for adults, double that for immunosuppressed, 5-10 for children less than 10)
Term
when are boosters recommended for HBV?
Definition
not recommended (invoke secondary IR). give to immunosuppressed pts and previously-vaccinated people who are exposed and who have circulating serum anti-HBs less than 10 mIU/mL
Term
why isn't a HCV vaccine available?
Definition
diversity of genotype makes it hard to make one
Term
what is the tx for acute HCV?
Definition
interferon alfa-2b. if not resolved in 3 mos give interferon alfa-2b + ribavirin (98% clearance)
Term
what is considered a "cure" in HCV?
Definition
viral RNA load suppression > 24 weeks
Term
what are the 5 drugs used to tx chronic HBV?
Definition
lamivudine, adefovir, entecavir, telbivudine, interferon alfa-2b
Term
what are the 5 drugs used to tx chronic HCV?
Definition
interferon alfa-2a, interferon alfa-2b, interferon alfacon-1, pegylated interferon alfa 2a, pegylated interferon alfa 2b
Term
lamivudine mode of action
Definition
(for chronic HBV) nucleoside analog (nucleoside reverse transcriptase inhibitor) --> phosphorylated by cellular kinases to active triphosphate form. competitively inhibits HBV reverse transcriptase and HBV DNA polymerase by competing with deoxycytidine triphosphate for incorporation into the viral DNA. chain termination after incorporation into viral DNA
Term
which 2 drugs for hepatitis are also used to tx HIV
Definition
lamivudine (originally for HIV, but longer half-life in HBV --> lower doses, fewer AE and increased safety); adefovir (aka tenovir) less toxic (lower) dose needed for HBV
Term
side effects/downside to lamivudine?
Definition
after rx, hbv returns and also drug resistance d/t mutations. after 1 year, 20% resistant. after 3 years, 50% resistant. few physical side effects: HA, insomnia, fatigue, gi discomfort
Term
how does adefovir work?
Definition
nucleotide analog to adenosine monophosphate --> phosphorylated by cellular kinases to active diphosphate form. used against lamivudine resistant viruses. competitively inhibits HBV DNA polymerase -> chain termination after incorporation into viral DNA
Term
side effects of adefovir
Definition
no significant drug resistance after 1 year (~4% after 3 yrs), hbv can reappear if tx stopped. physical side effects ~2% of patients, mild HA diarrhea GI discomfort
Term
how does entecavir work?
Definition
nucleoside analog to guanosine, more effective than lamivudine or adefovir (greater viral suppression, normalization of lfts, histo improvement). competitively inhibits hbv dna pol (blocks all 3 functions - base priming, reverse transcription and synthesis of positive strand)
Term
side effects of entecavir
Definition
no significant resistance; has not been proven safe for preg women; few adverse effects, HA fatigue GI discomfort
Term
how does telbivudine work?
Definition
nucleoside analog, phosphorylated by cellular kinases to active triphosphate form, may lead to greater hbv viral load reduction than lamivudine. competitively inhibits hbv dna pol and causes chain term when incorporated into viral dna
Term
side effects of telbivudine
Definition
lower incidence of resistance than lamivudine. few, mild sx: HA, insomnia, fatigue, GI discomfort. POTENTIAL ASSOC WITH peripheral neuropathy, myopathies, myalgias
Term
how do interferon alfas work?
Definition
they are cytokines that exert antiviral immunomodulatory and antiproliferative effects. syntheiszed by host cells and cause biochemical changes leading to an antiviral state in cells. bind to specific membrane receptors on the cell surface and initiate a series of intracellular events including enzyme induction, suppression of cell proliferation, immunomodulatory events, and inhibition of viral replication
Term
what factors make a person more responsive to interferon alfa tx for chronic HCV?
Definition
HCV genotype 2 or 3; absence of cirrhosis on liver bx; low pre-tx HCV RNA levels
Term
interferon alfacon 1 used for tx of?
Definition
chronic hcv
Term
interferon alfa 2a used for
Definition
chronic hcv
Term
interferon alfa 2b used for
Definition
acute hcv, chronic hcv, chronic hbv
Term
what does pegylating the interferons do?
Definition
(polyethylene glycol covalently bonded) extends half-life and slows clearance of the agents --> less frequent dosing
Term
what is the dosing for lamivudine, adefovir, entecavir, telbivudine?
Definition
oral, once daily
Term
how are interferons adminstered?
Definition
2a and 2b subcutaneous or IM; alfacon-1 and peg 2a peg2b --> subcutaneous (injections once a week)
Term
side effects of interferon alfas?
Definition
flu like sx within 6 hrs of dosing (>30% pts) usually resolves with continued administration; nausea, fatigue, HA, arthralgia, rash, alopecia, anorexia, hypotension, edema. thrombocytopenia, granulocytopenia, elevated LFTs, NEUROPSYCH effects (severe), ABORTIFACIENT
Term
what are the contraindications for use of interferon alfas?
Definition
psychosis, severe depression, neutropenia, thrombocytopenia, symptomatic heart disease, decompensated cirrhosis, uncontrolled seizures, hx of organ transplant (other than liver), pregnancy
Term
how does ribavirin work?
Definition
guanosine analog phosphorylated intracellularly by host enzymes. not fully clear, appears to interfere with synthesis of GTP to inhibit capping of viral mRNA and inhibit RNA-dependent RNA pol of certain viruses. inhibits replication of a wide range of DNA and RNA viruses
Term
side effects of ribavirin
Definition
hemolytic anemia (10-20%); depression, fatigue, irritability, rash, cough, insomnia, nausea, pruritis.
Term
contraindications in ribavirin use
Definition
anemia, end-stage renal failure, severe heart disease, pregnancy
Term
what do 5-aminosalicylates treat and how do they work?
Definition
mild to moderate IBD. 5-ASA modulates inflammatory mediators derived from both cyclooxygenase and lipoxygenase pathways, may also interfere with production of inflammatory cytokines since 5-ASA inhibits nf-kB (transcription factor for pro-inflam cytokines). all work topically, no systemic inhibition of cyclooxygenase pathways, which would exacerbate sx)
Term
azo compounds include which 3 specific drugs
Definition
sulfasalazine, balsalazide, osalazine
Term
how do azo compounds work?
Definition
5-ASA bound by an azo molecule (N=N) to an inert molecule or to another 5-ASA molecule. azo structure markedly reduces absorption of the parent drug from the small intestine. azo bond is cleaved by intestinal bacteria in the terminal ileum and colon releasing the active 5-ASA --> therefore high concentrations 5-ASA delivered to terminal ileum and colon
Term
what 2 specific drugs are mesalamine compounds?
Definition
pantasa, asacol
Term
how does pentasa work?
Definition
contains time release microgranules that release 5-ASA throughout the small intestine
Term
how does asacol work?
Definition
5-ASA packaged with pH-sensitive coating that dissolves at pH7 (pH of distal ileum and proximal colon)
Term
what are the side effects of 5-ASA drugs?
Definition
mostly well tolerated. any AE mostly due to sulfasalazine (not bc of the 5-ASA part, but bc of the sulfapyridine molecule). nausea, gi upset, arthralgia, myalgia, bone marrow suppression, malaise, hypersensitivity to sulfa --> fever, exfoliating dermatitis, pancreatitis, hepatitis, pericarditis, pneumonitis, hemolytic anemia; sulfasalazine also impairs folate absorption (give dietary supp of folate). up to 40% patients cannot tolerate AE of sulfasalazine
Term
what do we use glucocorticoids for in GI?
Definition
tx of moderate to severe IBD. not useful for disease remission (d/t side effects of long term use) use to kick patient into remission but cannot be used to maintain it so taper dosage
Term
what are how are prednisone/prednisolone administered and whats the dosage?
Definition
most commonly used oral glucocorticoid, can be given via iV in severely ill pts. immediate duration of biological activity allows for once-daily dosing. tx with initial oral dose of 40-60 mg/d --> pt responds in 1-2 weeks --> dose tapered to limit side effects
Term
what do we use hydrocortisone for? and how is it administered
Definition
for tx of IBD involving RECTUM or SIGMOID colon. administered as enemas, foam, or suppositories to maximize colonic tissue effects and minimize absorption with topical tx (15-20% still absorbed)
Term
what do we use budesonide for? and how is it administered?
Definition
synthetic analog of prednisolone, used for tx of mild to moderate crohn's involving ileum and proximal colon. given orally (subject of first-pass metabolism, low oral bioavailability) slightly less effective than prednisolone but with significantly less adverse systemic effects
Term
what do we use to achieve remission in IBD?
Definition
purine analogs - azathioprine and 6-mercaptopurine
Term
what are purine analogs (azathioprine and 6-mercaptopurine) used for?
Definition
remission of IBD; reduce/eliminate steroids in patients who depend on long-term glucocoritcoid rx to control active disease
Term
how do purine analogs work?
Definition
unknown.6-thioguanine causes inhibition of purine nucleotide metabolism and DNA synthesis and repair --> inhibition of cell proliferation
Term
what is the halflife of purine analogs?
Definition
less than 2 hrs but active metabolites (6 thioguanine nucleotides) are concentrated in cells --> prolonged half-life of days.
Term
side effects of purine analogs?
Definition
dose related. nausea, vomiting, bone marrow depression (immunosuppressive), hepatic toxicity (reversible with dose reduction). routine lab monitoring of blood count and LFTs required. hypersensitivity in 5% (rash, fever, diarrhea, pancreatitis, hep)
Term
what are the drug interactions of purine analogs?
Definition
allopurinol reduces metabolism of purine analogs; dose of purine analogs should be halved in pts takng allopurinol
Term
what is methotrexate used for and how is it administered?
Definition
antimetabolite used to achieve remission of crohn's disease. administered orally, subcutaneously, IM
Term
how does methotrexate work?
Definition
inhibition of dihydrofolate reductase. shares structural homology with interleukin-1, may interfere with its inflammatory actions and may stimulate release of adenosine, an endogenous anti-inflammatory autacoid. may stimulate apoptosis and death of activated t-lys
Term
side effects of methotrexate
Definition
only with high doses (not usually seen at the doses used for IBD) bone marrow depression, megaloblastic anemia, alopecia mucositis. folate supplementation to reduce occurance of side effects
Term
how does anti-tnf therapy help in IBD patients?
Definition
dysregulation of the TH1 T cell response is present in IBD (esp crohns) and tnf-alpha is one of the key pro-inflammatory cytokines. so regulating tnf-alpha wil help decrease the inflammatory response
Term
what is infliximab? how is it administered and what is it used for?
Definition
chimeric human-mouse monoclonal antibody to TNF-alpha. administered IV (half life 8-10 days, 2 weeks for clinical response). used in moderately severe and fistulating crohns disease (symptomatic improvement in 66% of patients and disease remission in 33%)
Term
how does infliximab work
Definition
binds soluble TNF-alpha --> prevents cytokine from binding to its receptors. also binds to membrane-bound TNF-alpha and neutralizes its activity. promotes complement activation and antibody-mediated cellular cytotoxicity of inflammatory cells
Term
side effects of infliximab?
Definition
infection d/t suppression of TH1 inflammatory response (pneumonia, sepsis); reactivation of latent tuberculosis (all pts must undergo purified protein derivative testing prior to tx. those with + test results must receive prophylactic therapy for tuberculosis)
Term
what is adalimumab and how is it administered?
Definition
fully human monoclonal antibody to human TNF-alpha (100% human); administered subcutaneously, halflife 2 weeks
Term
what is certolizumab and how is it administered
Definition
chimeric mouse-human monoclonal ab to human TNF-alpha (75% human). given subcutaneously halflife 2 weeks. antibody contains an FAB frag that is conjugated to PEG but lacks an Fc portion
Term
what are the 3 common antibiotics used in IBD therapy?
Definition
metronidazole, ciproflaxin, clarithromycin
Term
what type of drug is used to treat abdominal pain in IBS?
Definition
tricyclic antidepressants, no effect on mood at low doses, but appear to alter the processing of visceral pain information
Term
how do anti-spasmodics (anti-cholinergics) work?
Definition
inhibit muscarinic cholinergic receptors in the enteric plexus and on smooth muscle.
Term
what anti-spasmodics (anticholinergics) are used? what are the side effects?
Definition
dicyclomine (bentyl), hyosycamine (levsin); dry nose/mouth; visual disturbances; urinary retention (used only infrequently du/t AE)
Term
what are seratonin 5-HT3 receptor antagonists used for? (give specific one)
Definition
alosetron (lotronex); tx of severe diarrhea-predominant IBS in WOMEN. (50-60% report relief from pain, also reduces diarrhea)
Term
how do seratonin 5HT3 receptor antagonists work?
Definition
block 5HT3 receptors on enteric neurons to inhibit distension-induced sensory and motor reflex activation. also blocks central 5HT3 receptors to reduce responses to visceral stimulation. may also inhibit colonic motility.
Term
side effects of seratonin 5HT3 receptor antagonists
Definition
GI disturbances some of which are rare but serious. constipation (30%) and causes discontinuation in 10%. eschemic colitis in 0.3% --> fatal
Term
what are seratonin 5HT4 receptor agonists used for and how are they administered? (give specific name)
Definition
tegaserod (zelnorm) tx of constipation-prominent IBS. reduces abdominal pain, increases # of bowel movemnets per week, reduces hardness of stool. given orally, low bioavailability (10%) should be taken before meals since food reduces bioavailability.
Term
how do seratonin 5HT4 agonists work?
Definition
activation of 5HT4 receptors in mucosa stimulate peristalsis and gastric emptying. 5HT4 receptor activation also stimulates cAMP-dependent chloride secretion from colon --> increases stool liquidity
Term
side effects of seratonin 5HT4 receptor agonists
Definition
well tolerated. diarrhea (9%) resolves within first few days of tx. headaches (some)
Term
what is the drug used to tx gallstones and how does it work?
Definition
ursodial (actigall) = ursodeoxycholic acid, naturally occuring bile acid. decreases cholesterol content of bile by reducing hepatic cholesterol secretion. stabilizes hepatocite canalicular membranes
Term
who should take ursodial?
Definition
patients who are not candidates for gallstone surgery or who refuse cholecystectomy
Term
what are the luminal amebicides commonly used? what do they treat?
Definition
diloxanide furoate, iodoquinol, paromomycin; treat intestinal forms (only in lumen of bowel)
Term
what are the tissue (mixed) amebicides used? what do they treat?
Definition
metronidazole, tinidazole; intestinal and systemic (extraintestinal, bowel wall) forms treated, however less effective against amoeba in bowel lumen.
Term
what are the systemic amebicides used? what do they treat?
Definition
dehydroemetine, chloroquine; effective only against invasive forms, severe amebic dysentery or hepatic abscesses
Term
what is the tx for asymptomatic intestinal infection (amebiasis)?
Definition
luminal agent (80-90% effective); 10 day course 3x a day; check for no cysts in stool to prove cure
Term
what is the tx regimen for mild to moderate intestinal infection (amebiasis)
Definition
tissue agent + luminal agent; 90% effective (tx lumen, bowel wall and liver inf) check stool to make sure no cysts being passed
Term
what is the tx regimen for severe intestinal infection (amebiasis) with dysentery?
Definition
tissue agent + luminal agent; management of fluids and electrolytes necessary; opioids given to control bowel motility; give antidiarrheal to tx symptoms wil we wait for anti-protozoal to kick in
Term
what is the tx regimen for hepatic abscess in amebiasis?
Definition
tissue agent + luminal agent + chloroquine (recommended); metronidazole effective against anaerobes in abscess; must give luminal agent even if organism not detected in stool bc 10% relapse rate if luminal agent not given d/t latent infection
Term
what is the tx regimen for extraintestinal infection, ameboma?
Definition
tissue agent + luminal agent
Term
describe the use and administration of iodoquinol
Definition
oral; effective against trophozoites and CYSTS; used as monotherapy to treat asymptomatic intestinal infections or in combination with metronidazole for moderate to severe intestinal infection and extraintestinal infection. not well absorbed in the intestine (90% remains in bowel lumen --> reaches good therapeutic levels in lumen)
Term
what are the side effects of iodoquinol?
Definition
diarrhea (limited duration); nausea, vomiting, anorexia, abd pain, HA, rash, pruritis. may increase protein-bound serum iodine concentration leading to decreased iodine uptake and potential iodine deficiency. contraindicated in patients with intolerance to iodine; potential for NEUROtoxicity at higher than recommended dose.
Term
describe the use and administration of paromomycin
Definition
oral; aminoglycoside antibiotic; used as monotherapy for asymptomatic intestinal infections or in combination with metronidazole for more severe intestinal infections. not absorbed from GI tract (except with ulcerative intestinal lesions, impaired motility or intestinal obstruction)
Term
how does iodoquinol work?
Definition
unknown
Term
how does paromomycin work?
Definition
inhibition of protein synthesis
Term
side effects of paromomycin
Definition
safe if not absorbed. absorption occurs if bowel is perforated --> nephrotoxicity, ototoxicity, abdominal distress, diarrhea. drug should be avoided in patients with renal disease and used with caution in patients with GI ulcers
Term
describe diloxanide furoate use and administration
Definition
(only available thru CDC) oral; drug of choice for monotherapy for asymptomatic intestinal infections d/t low incidence of AE but no longer commercially available. used in combo with metronidazole for moderate to severe intestinal infections as well as extraintestinal inf.
Term
how does diloxanide furoate work?
Definition
unknown
Term
side effects of diloxanide furoate?
Definition
well tolerated (mild). flatulance (most common), nausea, vomiting, diarrhea, cramps, pruritis, urticaria
Term
describe the use and administration of metronidazole in protozoal infections
Definition
oral (90% bioavailability), IV, intravaginal, topical; potent antibac activity against anaerobes, drug of choice for trichomoniasis and giardia lamblia; used in combo with luminal agents to treat mild to seere intestinal ambeiasis and extraintestinal amebiasis; alternative to tetracyclin in tx of balantidium coli
Term
how does metronidazole work against protozoa?
Definition
prodrug --> hydroxymethyl metronidazole (reduced to active form in protozoa and anaerobes) --> reacts with DNA. only active against trophozoites
Term
side effects of metronidazole
Definition
nausea, vomiting, dry mouth, metallic taste, anorexia, abd pain; CNS probs with prolonged therapy (seizures, peripheral neuropathy, avoid in patients with CNS disease esp seizure disorders); metabolites potentially mutagenic (contraindicated in first trimester of preg, enters fetal circ rapidly, breast feeding not rec); disulfram like side effects (inhibits alcohol dehydrogenase, ethanol avoided); candida overgrowth; pancreatitis (serious, rare); leukopenia (rare, use with caution in patients with previous or active bone marrow suppression)
Term
when can tinidazole substitute for metronidazole?
Definition
amebiasis, giardia, trichomoniasis
Term
describe the use and administration of dehydroemetine
Definition
subcutaneous, IM (NEVER IV); alternative component of combination therapy (with luminal agent) in patients who dont respond to or are contraindicated for metronidazole use. used to treat severe intestinal amebiasis or extraintestinal amebiasis; works in ALL tissues
Term
how does dehydroemetine work?
Definition
inhibition of protein synthesis
Term
side effects of dehydroemetine?
Definition
cardiotoxicity (arrhythmias, conduction defects); prolongs QT, PR, QRS, ST) hypotension 25%. not a front line drug d/t these AE, metronidazole is preferred
Term
describe use and administration of chloroquine
Definition
oral, parenteral; used in combination therapy to treat amebic LIVER abscesses. much less effective against intestinal amebiasis bc only attains low concentrations in the intestinal wall.
Term
mechanism of chloroquine action
Definition
unknown
Term
side effects of chloroquine
Definition
well tolerated. pruritis (most common, esp africans), nausea, vomiting, abd pain, HA, anorexia, malaiase, blurring vision, urticaria. dosing after meals to reduce AE
Term
how/why is tetracycline used against protozoa?
Definition
used as an alternative to metro in multi-drug regimens in mild to severe intestinal amebiasis. (only for infections of the bowel wall). has only weak amebicidal actions, alters GI flora needed for amebic proliferation.
Term
what do we use to treat balantidium coli?
Definition
tetracycline (alternatives: metro, iodoquinol)
Term
what do we use to treat cryptosporidium parvum?
Definition
paromomycin or nitazoxinade (alternative: azithro)
Term
what do we use to treat cyclospora cayentanensis?
Definition
TMP-SMX
Term
what do we use to treat giardia lamblia?
Definition
metronidazole or nitazoxinade (alternative: tinidazole, furazolidone, albendazole)
Term
what do we use to treat isospora belli?
Definition
TMP-SMX
Term
what do we use to treat microsporidia?
Definition
albendazole
Term
what do we use to treat trichamona vaginalis?
Definition
metro or tinidazole
Term
what do we use furazolidone for and how does it work?
Definition
alternative to metro in tx of giardia lamblia. damages worm DNA; given orally with good bioavailability
Term
side effects of furazolidone?
Definition
nausea, vomiting, diarrhea, fever; disulfram-like activity (no etoh); acts as monoamine oxidase inhibitor (hypertensive crisis can be induced by increased norepinephrine availability following tx with sympathomimetics)
Term
describe the use and administration of nitazoxanide
Definition
oral (prodrug --> tizoxanide); tx giardia and cryptosporidium, effective against metronidazole resistant protozoal strains
Term
nitazoxanide mechanism of action?
Definition
its active metabolite (tizoxanide) inhibits the pyruvate:ferredoxin oxidoreductase pathway
Term
side effects of nitazoxanide?
Definition
well tolerated. metabolites free of mutagenic effects (lower risk for preg or breast feeding women than metro)
Term
describe the use and administration of TMP-SMX in protozoal tx
Definition
used to treat cyclospora cayentanensis and isospora belli
Term
how does TMP-SMX work?
Definition
disrupts folic acid synthetic pathway
Term
what do we use to treat ascaris lumbricoides?
Definition
mebendazole or albendazole or pyrantel pamoate (alternatives: ivermectin, piperazine)
Term
what do we use to treat enterobius vermicularus?
Definition
mebendazole or albendazole or pyrantel pamoate
Term
what do we use to treat hookworms?
Definition
mebendazole or albendazole or pyrantel pamoate
Term
what do we use to treat strongyloides?
Definition
ivermectin (alternatives: albendazole or thiabendazole)
Term
what do we use to treat trichuris trichura)?
Definition
mebendazole or albendazole (alternative: ivermectin)
Term
what do we use to treat trichinella spiralis?
Definition
mebendazole or albendazole (add corticosteroids for severe inf to reduce the stimulation of the immune response by antigens released by dying worms)
Term
what do we use to treat schistosoma?
Definition
praziquantal
Term
what do we use to treat clonorchis sinensi?
Definition
praziquantal (alternatives: mebendazole or albendazole)
Term
what do we use to treat diphyllobothrium latum?
Definition
praziquantal or niclosamide (not available in US)
Term
what do we use to treat taenia saginata?
Definition
praziquantal or niclosamide (not avail in US) alt: mebendazole
Term
what do we use to treat taenia solium?
Definition
praziquantal or niclosamide (not avail in US)
Term
what do we use to treat cysticercosis?
Definition
albendazole (alt: praziquantal) - albendazole is effective >80% for cystericosis secondary to T solium. it is the ONLY agent used for tx of ocular neurocystericosis
Term
how does mebendazole work?
Definition
irreversibly and selectively damages helminth microtubules --> accumulation of catabolic enzymes --> cell autolysis --> worm death. loss of microtubules also decreases glucose uptake --> starves worm --> contributes to death.
Term
how is mebendazole administered?
Definition
oral: poor bioavailability, minimal absorption and significant first pass metabolism
Term
contraindications for mebendazole use?
Definition
not for preg women or children <1 year old
Term
albendazole mechanism of action?
Definition
similar to mebendazole (damages helminth microtubules, decreases glucose uptake)
Term
albendazole mechanism of action?
Definition
similar to mebendazole (damages helminth microtubules, decreases glucose uptake)
Term
contraindications for albendazole use?
Definition
not for preg women, breastfeeding women, or kids <2. should be monitored carefully if co-treated with theophylline, phenytoin or digoxin
Term
pyrantel pamoate is the drug of choice for which 3 worms?
Definition
ascaris, enterobius, hookworm
Term
how does pyrantel pamoate work?
Definition
acts on helminth neuromuscular junction by inhibiting acetylcholinesterase and stimulates acetylcholine release --> paralysis --> worm released from intestinal wall --> GI peristalsis expels the worms
Term
how is pyrantel pamoate administered?
Definition
oral; poorly absorbed from GI tract, more than 50% excreted unchanged in feces
Term
ivermectin is the drug of choice for?
Definition
strongyloides
Term
how does ivermectin work?
Definition
potentiates the opening of glutamate-gated chloride channels found in nematodes but not humans --> paralysis of worms pharyngeal muscle --> death of parasite. also potentiates gaba-mediated inhibitory synaptic transmission in peripheral nerves --> contributes to paralysis (flaccid paralysis vs pyrantel pamoate which is tense paralysis)
Term
how is ivermectin administered?
Definition
oral, single dose usually sufficient to expel worms in over 80% of patients. repeated dosing will increase cure rate
Term
contraindications for use of ivermectin?
Definition
pregnant women, not for patients with possible impairments of the BBB (i.e. meningitis) bc of GABA effects
Term
how does piperazine work?
Definition
blocks acetylcholine at the neuromuscular junction --> muscle paralysis --> dislodged and expelled by normal peristalsis
Term
contraindications for use of piperazine?
Definition
pregnant women, impaired renal or hepatic function, hx of epilepsy or chronic neurological disease (can cause neurotoxicity in rare cases)
Term
how does thiabendazole work?
Definition
interfere w/microtubule aggregation thru inhibition of fumurate reductase (ovicidal effects?)
Term
side effects of thiabendazole?
Definition
(7-50%) midl and transient, can be severe. nausea, vomiting, anorexia, dizziness...drowsiness, diarrhea, pruritis, neuropsych sx, hepatic dysfunc (rare)
Term
contraindications for thiabendazole use?
Definition
pregnant woman, daytime use limited d/t drowsiness/dizziness; patient should be monitored carefully if co-treated with theophylline or other xanthine derivatives
Term
how is praziquantal given?
Definition
oral; single dose usually effective
Term
how does praziquantal work in general?
Definition
increases permeability to calcium ions and damages integument
Term
describe how praziquantal works in schistosomiasis
Definition
increases permeability to calcium ions --> calcium influx induces tetanus and paralysis of worm muscles --> rapid and powerful vacuolation of tegument --> adult worms swept to liver, endocytosed by phagocytes. praziquantel exposes worm antigens and facilitates the IR, should not be given in acute schistosome disease (katayama) d/t additonal antigenic burden from dying immature worms which may exacerbate sx.
Term
how does praziquantal work in tapeworms (diphyllobothrium, taenia saginata and solium)
Definition
increases permeability to calcium ions --> calcium release from intracellular stores --> massive worm contraction --> expulsion from GI
Term
how is praziquantal administered?
Definition
oral; single dose, must be swallowed w/o chewing d/t bad taste. enters CSF, bile, breast milk
Term
contraindications for use of praziquantal?
Definition
pregnant women, breast feeding discontinued for 72 hrs following tx.
Term
what is the risk in treating t.solium with niclosamide?
Definition
viable ova are released by drug-damaged worms into the intestine --> can develop into larvae and cause cysticercosis
Term
how does niclosamide work?
Definition
uncoupling of worm oxidative phosphorylation --> increase ATPase activity --> starves worm
Term
how is niclosamide giveN?
Definition
oral; single dose, minimal GI absorption
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