Drug Interactions Flashcards
Drug interactions
one drug affects the response of the second drug given at the same time
Pharmacokinetic interactions
occur during absorption, distribution, metabolism, elimination. - Tetracycline &Iron, Tetracycline and Calcium, Furosemide and Magnesium hydroxide
Pharmacodynamic iterations - synergism
2 drugs act in the same direction, adm. together
Pharmacodynamic interactions - addition synergism
total effect is sum of effects of each considered separately - Aspirin and paracetamol
PD Int - enhancing synergism
total effect greater than sum of effects of each separately - direct: same direction but diff mech of action - Penicillin and Kanamycin,
-indirect:L one drug suppresses antagonist action of the other - sympatholytics with insulin (hypoglycemia)
Antagonism
opposing actions, one drug will be abolished by second drug : chemical (neutralizing like aspirin and sodium bicarbonate), physiologic (different receptors and effects cancelled, sympathetics ¶symp), pharmacologic (antagonist stops agonist from acting on receptors)
Drug interactions can be
increased effect, decreased effect, desired consequences, adverse effect(toxic)
Drug related adverse affect factors
physical and chemical char., dose, route, pharmacokinetic
Patient related adverse effect factors
age, gender, genetics, physiologic, pathologic
Toxic reactions
dose related, direct action of drugs upon tissues
Hepatotoxicity
Paracetamol, isoniazid, halftone, rifampicin, amphotericin B
Renal toxicity
Furosemide, phenacetin, aminoglycosides
Medular toxicity
cytostatic, Chloramphenicol
Teratogenic reactions
adm in 1st 3 months pregnancy: anticancer, aminoglycosides, oral anticoagulants, androgen/estrogen, Phenitoines
Mutagenic
changes in genotype and phenotype (after many gen), anticancer, Metronidazole, anti epileptics, neuroleptics
Carcinogenic
aminophenazone, cimetidin
Idiosyncratic adverse events
not dose related, occur because of genetic predisposition, abnormal response of body: decrease in g6p and high risk of severe hemolysis after Nitrofurantoine, Furazolidone, Doxorubicine, Nalidixic acid, Phenacetin.
Immunoallergic adverse events
are not dose related
Type I (anaphylactoid)
immediate, coupling of antigen to IGE from surface of mastocytes and basophilic cells causing release of histamine, kinine, leukotriene, prostaglandin, most severe is anaphylactic shock
type II (cytotoxic)
reaction between antibody between IGG and IGM Andy cells that are antigenic because of fixing of drug, result in blood cell lysis
Type II examples
hemolytic anemia (penicillins, rifampicin), granulocytopenia(aminophenazone), thrombocytopenia (quinidine, sulfamides, thiazidine, diuretics)
Type III (immune complex)
complex between antigen and IGG and IGM will be fixed on small vessels or basal membranes, causing inflammatory reactions
Type III examples
serum sickness (sulfonamides, penicillins, antiepileptics, antithyroidians), quince edema, rash (aspirin, penicillins), vascularitis, polymorphorphic edema, Steven Johnson erythema
Type IV (cell mediated)
delayed reaction, sensitized T cells release lymphokines producing inflammation and edema
Type IV example
contact dermatitis after local ads of neomycin or kanamycin
Tolerance type adverse effects
Tachyphylaxis, mitridiasm, dependence
Tachiphylaxis (acute tolerance)
decrease effect of intensity, suddenly after repeated administrations, because of chemical mediator depletion or prolonged receptor blockage :sympathomimetics
Mitridatism
organism tolerates doses that otherwise induces nociceptive effects after first admin. : atropine, arsenic, nicotine
Dependence (tolerance by repeated admin.)
psychological, physical, tolerance, psychotoxicity
Psychological dependence
psychological need to use a drug in order to obtain an affective effect
Physical dependence
need to continue admin to prevent symptoms (abstinence syndrome):anxiety, apathy, insomnia, anorexia, nausea vomit, diarrhea, sweating, lacrimtion, diffuse pain, CV rest, blood pr osc
Tolerance
progressive diminution of effect after repeated admin, necessity to increase dose to obtain desired effect
Psychotoxicity
morphine, heroin, cocaine, opium, LSD