| antagonists | actions | uses of blockers | side effects | |
| histamine | 1-physiologic antagonists :eg adrenaline # effect of hist on sk mu so used in anaphylactic shock 2-drugs w prevent hist release eg cromolyn sod ,nedocromil sod ,adrenal steroids ,B2 agonists 3-hist receptor blocker | |||
| H1 blockers | A) old (w is lipid sol ,pass cns ,sedatn & drowsness ,has low duration of action 4-6 hrs ) :diphenhydramine (dramamine) ,chlorpheniramine ,meclizine ,cyproheptadine (periactin) ,promethazine (phenergan) new (2nd generation ,no sedation ,high duration of action 12hrs ,route :orally or parentrally IM or IV) :astimazole ,loratidine ,terfenadine ,fexofenadine | 1-antihistaminic action : A) on CV 1-vasodilatation so () bl.p 2-+ HR 3-flushing ,headache 4-oedema B)smooth mu >spasmogenic w lead to 1-bronchospasm 2-GIT motility 3-contractn of uterus C)nerve ending >stim >pain and itching 2-direct action : 1-sedation (old drugs) ,toxic dose >cns stim >convulsions in children 2-anti muscarinic or atropine like action 3-antiemetic action 4-antiparkinsonian effect 5-local anaesthetic as block Na channels 6-block - adrenoreptors >hypotension **periatin block H1 receptor & S-HT receptor (anti serotonin action) | 1-ttt of allergic Rx as urticaria ,allergic rhinitis ,bronchial asthma 2-ttt of motion sickness (anti emetic effect of dramamine) 3-in cough mix > chlorpheniramine | 1-sedation (old drugs) ,high dose >cns stim >convulsions in children (chlorpheniramine) 2-dry mouth ,blured vision (due to atropine like effect) |
| H2 blockers | cimetidine ,nizatidine ,ranitidine ,farmotidine block H2 receptor | 1-block H2 receptor in GIT > inhibition of gastric HCl sec *nizatidine (disadv) block H2 receptor in cardiac mucle cause bradycardia ,() cardiac output *ranitidine ,cimitidine >() renal exc of basic drugs *cimitidine has anti androgenic effect blocks androgenic receptor & inhibition of oxidative drug metabolizing enz | 1-ttt of peptic & duodenal ul;cers 2-ttt of gastro esophagial reflex (GER) 3-ttt of hyper sec of gastric juice | common : 1-diarrhea 2-skin rashes 3-headache ** cimitidine : 1-Gynecosmastia in male () sperm count and reversible impotence *galactorrhea in female 2-liver toxicity in form of reversible cholestatic effect 3-CNS stim in old pateints |
| Serotonin | 1-cyproheptadine 2-ketanserin 3-ondanseteron 4-ritanserine | 1-cyproheptadine : H1 blocker & 5-HT blocker ,antagonise spasmogenic action of both hist & serotonin ,*it has antimuscarinic effect *has sedative action 2-ketanserine :*antagonise serotonin recep 1,2 and a1 -adrenoceptors (N.B) 5-HT 2 on bl platelets surface >inhibition of platelets aggregatn > + bleeding time 3-ondanseteron : block 5-HT3 in brain *used in ttt of nausea & vommiting accompanied by chemotherapy of cancer (antiemetic action) 4-Ratanserine : action only on 5-HT 2 (increase bleeding time) | ||
| Angiotensins | A) inhibitors of Renin secretion :1-methyl dopa 2-propranolol 3-clonidine B) renin inhibitors eg pepstatin C)Angiotensin converting enz inhibitors (ACEI) eg 1-Enalapryl 2-Captopril both in ttt of hypertension D)Angiotensin inhibitor eg Saralasin > antihypertensive (IV) | |||
| eicosanoids (Pgs ,Lts ,TxA2) | action PGI2 PGE2 PGD2 PGF2a TXA2 bl.v V.D of arteries --------- V.C of veins bronchial muscle bronchorelaxation bronchoconstriction platelet aggregation decrease --------- --------- --------- increase oxytocic action --------- potent --------- less potent -------- neurotransmitter ----------- decrease NE release ----- --------- --------- | |||
| leucotrienes | action 1-severe bronchospasm 2-mucous hypersec 3-VC 4-chemoattraction of leucocytes (eisinophils ,monocytes) | |||