Medchem II - Antihistamine

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Pharmacy Flashcards on Medchem II - Antihistamine , created by Lourdes Khalil on 18/05/2021.
Lourdes Khalil
Flashcards by Lourdes Khalil, updated more than 1 year ago
Lourdes Khalil
Created by Lourdes Khalil almost 3 years ago
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Question Answer
-histidine -precursor of histamine -undergoes aa decarboxylation by HDC (histidine decarboxylase) to give histamine
-histamine -biologically active amine -functions as autacoid -works in plants, animals and all organs of human body -chemical mediator of hypersensitivity (H1 R) -regulator of acid secretion (H2 R) -NT in the brain (H2 & H4 R) -stored in mast cells after synthesis
-betahistine -only antihistamine that has therapeutic use -treats vertigo indirectly by being strong H3 A- and directly by being weak H1 A+
-khellin -inhibitor of histamine release -chromone -prevent bronchospasm but does not reverse antigen induced bronchoconstriction
-cromolyn sodium -inhibitor of histamine release -chromone derivative -no bronchodilator effect -no anti-inflammatory effect -COO- -> hydrophilic -> poor absorption -> low oral bioav
-nedocromil sodium -inhibitor of histamine release -chromone derivative -no bronchodilator effect -no anti-inflammatory effect -COO- -> hydrophilic -> poor absorption -> low oral bioav
both cromolyn sodium and nedocromil sodium -strictly prophylactic -by inhalation for bronchial asthma -as nasal solution for allergic rhinitis -topical: eye drops for allergic conjunctivitis -given 5-30min before attack -chronic use may lead to tolerance
-Lodoxamide -inhibitor of histamine release -mast cell stabilizer -> inhibits the immediate hypersensitivity reaction -used topically for TTT of conjunctuvitis
-pemirolast potassium -inhibitor of histamine release -pyrimidinone derivative -has acidic tetrazole -used topically to prevent allergic conjunctivitis -inhibits release of inflammatory mediators and leukotrienes
-phenbenzamine -1st gen antihistamine H1 -ethylenediamine derivative
-tripelennamine -1st gen antihistamine H1 -ethylenediamine derivative -replaced the phenyl of phenbenzamine by 2-pyridyl
-thonzylamine -1st gen antihistamine H1 -ethylenediamine derivative -replaced by 2-pyrimidyl -cause sedation, drowsiness, may impair mental activity
-cyclizine -1st gen antihistamine H1 -ethylenediamine piperazine derivative -orally active -TTT of nausea due to motion and radiation sickness -IM injection (cyclizine lactate)
-chlorcyclizine -1st gen antihistamine H1 -ethylenediamine piperazine derivative -the Cl para substitution blocked the inactivating aromatic hydroxylation -piperazine is a bit hydrophilic & Cl is a bit lipophilic -> good distribution + can be given orally -antiallergic for urticaria and hay fever
-hydroxyzine -1st gen antihistamine H1 -ethylenediamine piperazine derivative -antiallergic for pruritis, antiemetic, marked sedation -high dose -> emotional stress & anxiety
-cetirizine -2nd gen antihistamine H1 -ethylenediamine piperazine derivative -COOH and N will be ionized -> zwitterion-> cannot cross BBB -> no sedation -carboxylic acid metabolite of hydroxyzine -levo 30x> dextro (levocetirizine is marketed)
-meclizine -1st gen antihistamine H1 -ethylenediamine piperazine derivative -TTT of nausea due to motion &radiation sickness
-buclizine -1st gen antihistamine H1 -ethylenediamine piperazine derivative -TTT of nausea due to motion &radiation sickness
-oxatomide -1st gen antihistamine H1 -ethylenediamine piperazine derivative -special substitution: N-benzimidazole-2-one -antimuscarinic -mast cell stabilizer -> inhibit release of histamine (should be given abel bwa2et to decrease allergy)
-diphenhydramine -1st gen antihistamine H1 -ethanolamine ether/aminoalkyl ether -antihistamine, antiemetic, marked sedation, anticholinergic, antidyskynetic, antitussive -p-methyl subs -> decrease anticholi, increase antihist -o-methyl subs -> increase anticholi, decrease antihist -3ary amine into 4nary amine -> increase anticholi, decrease antihist
-dimenhydrinate -8-chlorotheophylline salt of diphenhydramine -for motion sickness
-bromodiphenhydramine -1st gen antihistamine H1 -ethanolamine ether/aminoalkyl ether -more lipid soluble -more potent
-chlorodiphenhydramine -1st gen antihistamine H1 -ethanolamine ether/aminoalkyl ether -more lipid soluble -more potent
-carbinoxamine -1st gen antihistamine H1 -ethanolamine ether/aminoalkyl ether -potent antihistamine -levo > potent than dextro
-doxylamine -1st gen antihistamine H1 -ethanolamine ether/aminoalkyl ether -same potency as diphenhydramine -more potent CNS depressant -> used as hypnotic agent
-setastine -1st gen antihistamine H1 -ethanolamine ether/aminoalkyl ether
-clemastine -1st gen antihistamine H1 -aminoalkyl ether -NOT ethanolamine ether bcz 3C bw O&N -2 chiral centers: RR is >> potent than others -potent antihistamine -long DOA -less sedative+ less anticholi -> good thing (bcz of propyl)
-pheniramine -1st gen antihistamine H1 -alkylamine derivatives -saturated
-chlorpheniramine -1st gen antihistamine H1 -alkylamine derivatives -saturated -10x more potent than pheniramine -dextro > levo -longer t1/2 -> longer acting than pheniramine
-brompheniramine -1st gen antihistamine H1 -alkylamine derivatives -saturated -more potent than pheniramine (similar potency as chlorpheniramine) -dextro> levo -longer acting than chlorpheniramine
-triprolidine -1st gen antihistamine H1 -alkylamine derivatives -unsaturated -relatively potent antihistamine -relatively long acting -E isomer > Z isomer -distance bw 3ary amine and 1 of the Ar rings is essential for binding
-pyrrobutamine -1st gen antihistamine H1 -alkylamine derivatives -unsaturated -relatively potent antihistamine -relatively long acting -E isomer > Z isomer -distance bw 3ary amine and 1 of the Ar rings is essential for binding
-dimethindene -1st gen antihistamine H1 -alkylamine derivatives -unsaturated -potent antihistamine -levo > dextro
-phenindamine -1st gen antihistamine H1 -alkylamine derivatives -unsaturated -moderately potent -may cause CNS stimulation& insomnia in some patients
-promethazine -1st gen antihistamine H1 -tricyclic antihistamine -specialized form of ethylenediamine -highly sedative -for seasonal allergic rhinitis, pruritis
-pimethixene -1st gen antihistamine H1 -tricyclic antihistamine, phenothiazine -replacement of the N10 in phenotiazine by C= -orally active
-metixene -1st gen antihistamine H1 -tricyclic antihistamine, phenothiazine -moderate antihistamine -marked anticholi -> useful in parkinson's
-cyproheptadine -1st gen antihistamine H1 -tricyclic antihistamine, phenothiazine -replaced the 6 membered ring in pimethixene by a 7 membered ring (ring equivalent isostere of pimethixene) -antihistamin, antisrotonin, anticholi, appetite stimulant (good for AN)
-azatadine -1st gen antihistamine H1 -tricyclic antihistamine, phenothiazine -aza isostere of 10,11-dihydrocyproheptadine (reduced the =, added N to a ring) -potent -long acting antihistamine, anticholi
-ketotifen -1st gen antihistamine H1 -tricyclic antihistamine, phenothiazine -thiophene ring equivalent of 9,10-dihydro-10-keto derivative of cyproheptadine -potent antihistamine -mast cell stabilizer -> inhibits the release of histamine
-fexofenadine -2nd gen antihistamine H1 -active non toxic metabolite of terfenadine -marketed on its own
-mizolastine -2nd gen antihistamine H1 -long acting -non sedating -chemical structure similarity w/ astemizole -metabolized into inactive
-loratadine -2nd gen antihistamine H1 -ethyl carbamate derivative of azatadine -tricyclic long acting non-sedating antihistamine -low affinity for CNS transporting proteins -active
-desloratadine -2nd gen antihistamine H1 -loratadine metabolite (after hydroxylation -> hemiacetal -> hydrolysis -> carbamic acid -> decarboxylation -> desloratadine) -2ndary amine -marketed on its own -active
-acrivastine -2nd gen antihistamine H1 -added propenoic acid at position 2 of pyridine of triprolidine (1st gen) -zwitterion -> lack CNS effects
-terfenadine -2nd gen antihistamine H1 -1st nonsedating H1 antihistamine -cardiotoxic (bcz it's a CYP3A4 inhibitor): QT prolongation, torsade de pointes -discontinued from the market, associated with life threatening cardiac arrhythmias
-ebastine -2nd gen antihistamine H1 -amino alkyl alcohol of terfenadine -> to benzhydryl ether butyrophenone derivative -potent long acting non sedating H1 antihistamine agent
-azelastine -2nd gen antihistamine H1 -topical antihistamine -seasonal allergic conjunctivitis -nasal spray for allergic rhinitis
-olopatadine -topical antihistamine -2nd gen antihistamine H1 -seasonal allergic conjunctivitis -nasal spray for allergic rhinitis
-emedastine difumarate -topical antihistamine -2nd gen antihistamine H1 -seasonal allergic conjunctivitis -nasal spray for allergic rhinitis
-alcaftadine -topical antihistamine -2nd gen antihistamine H1 -seasonal allergic conjunctivitis -nasal spray for allergic rhinitis
-epinastine (HCl) -topical antihistamine -2nd gen antihistamine H1 -seasonal allergic conjunctivitis -nasal spray for allergic rhinitis
-ketotifen fumarate -topical antihistamine -2nd gen antihistamine H1 -seasonal allergic conjunctivitis -nasal spray for allergic rhinitis
-4-methylhistamine -highly selective H2 agonist -binds through this conformation II to H2 receptor
-N-guanylhistamine -replaced the NH3+ of histamine by a polar functional grp: guanidine -partial agonist
-isothiourea histamine -A- activity on H2 R increased but still was a partial agonist
-SFK 91581 -weak A- with no A+ activity (to H2)
-burimamide -highly specific competitive A- at H2 R -100x more potent than N alpha guanylhistamine -problem: activity too low for oral absorption -> work on imidazole ring -see which tautomer is preferred and see the protonated intermediate -chain is electron donating -> make it withdrawing to decrease ionization and bind better to H2 R
-thiaburimamide -presence of S (EWG) decreased pka -> decreased ionization -> increase A- activity (to H2) -non-ionized imidazole is favored
-metiamide -added a 4-methyl (EDG) to thiaburimamide -10 fold increase in A- activity (to H2) compared to burimamide -favors tautomer I over II -unacceptable SE: kidney damage
-cimetidine -has cyanoguanidine -presence of CN (strong EWG) -> less basic + less ionized -> best potency -comparable activity to metiamide -less SE -inhibits H2 R+ lowers the gastric acid released -biggest selling prescription drug until ranitidine (new antihistamine H2 R) -metabolically stable -inhibit CYP450 -antiandrogenic effects -inactive major metabolite: S-oxide
-ranitidine -2nd gen H2 antagonist -non-imidazole derivative -has furan ring -has dimethyl amino -NO2 is EWG instead of CN of cimetidine -orally active w/ oral bioav of 30-80% -4-10x > potent than cimetidine -no SE of cimetidine: no antiandrogenic effect + weaker inhibitor of CYP
-nizatidine -2nd gen H2 antagonist -non-imidazole derivative -has thiazole ring -has dimethyl amino -NO2 is EWG instead of CN of cimetidine -5-18x > potent than cimetidine -no CYP inhibition + no antiandrogenic effect -oral bioav: 75-100% -renal elimination
-famotidine -2nd gen H2 antagonist -non-imidazole derivative -has thiazole ring -has guanitidine instead of dimethyl amino of ranitidine & nizatidine -has sulfonamide instead of nitro -more potent -low bioav: 40-45% -no inhibition of CYP + no antiandrogenic effect
-PPI pharmacophore/ scaffold -2-pyridylmethylsulfinylbenzimidazole derivative -sulfinyl moiety is chiral: R & S isomers
-sulfenic acid intermediate in the MOA of PPI -binds irreversibly to the PP by forming disulfide bond S=S with the cysteine
-sulfenamide intermediate in the MOA of PPI -binds irreversibly to the PP by forming disulfide bond S=S with the cysteine
PPIs -omeprazole -esomeprazole -tenatoprazole -lansoprazole -rabeprazole -pantoprazole
-misoprostol -semisynthetic ester prodrug derivative of PGE1 -absorbed as prodrug -> de-esterified -> active metabolite -not metabolized by 15-hydroxy PG dehydrogenase -PGE1 preserves the integrity of the gastric mucosa
-sucralfate -miscellaneous agent -aluminum hydroxide complex of octasulfate ester of sucrose -minimal amounts are absorbed systematically -binds to the ulcer site, prevent exposure of ulcerated area to gastric acid -stimulates synthesis and release of PG (protective effect) + bicarbonate (neutralize acid) + epidermal and fibroblast growth factors (protective effect) -DDI: reduce absorption of: H2 antihistamine, warfarin, quinolone AB, phenytoin
-carbenoxolone -miscellaneous agent -steroid like structure from licorice -unique feature: very long chain at position #3 -no clear MOA: has mineralocorticoid activity + inhibit PG inactivation -major SE: due to mineralocorticoid activity
-pirenzepine -anticholinergic -selective M1 R A- -block M R -> decrease gastric acid secretion & intestinal motility -quaternary ammonium are preferred
-telenzepine -anticholinergic -selective M1 R A- -block M R -> decrease gastric acid secretion & intestinal motility -quaternary ammonium are preferred
systemic antacid -sodium bicarbonate -NaHCO3 + HCL -> NaCl +CO2 -release of CO2 -> stomach distention -sodium load -> salt & water rentention -alkalosis
calcium carbonate -non systemic antacid -CaCO3 + HCl -> CaCl2 + H2O + CO2 -release of CO2 -> stomach distention -10% is absorbed -> hypercalcemia -> Ca stone in kidney -alkalosis
aluminum hydroxide gel -non systemic antacid -neutralizes HCL w/o forming CO2 -Al(OH)3 + HCl -> HCl3 + H2O -disadvantages: constipation + DDI: decrease absorption of digoxin, tetracycline and iron
-magnesium trisilicate -non systemic antacid -neutralize HCl w/o forming CO2 - Mg Tri + HCl -> MgCl2 + H2O + silicone dioxide gel -disadv: diarrhea + CNS depression + contraindicated in renal failure due to Mg excretion
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