pharmactherapeutics Flashcards
explain repeat administration
is a drug that is eliminated by first order kinetics is administered repeatedly, the average plasma conc of the drug will increase to a steady state level
will drugs that show zero order elimination be able to reach steady state level
no
what is the time required to reach steady state level
5 half lives
how do we control the magnitude of fluctuations in steady state level
by using a dosing interval
what will a shorter dosing interval do to the fluctuations
decrease them
what will a longer dosing interval do to the fluctuations
increase them
on cessation of multidose administration what will happen to the drugs elimination
94-97% of the drug will be eliminated in a time interval equal to five half lives
how high is the mean of the plasma conc during steady state in relatio to the Cmax after first application
its 1.44 time higher
when should we use a loading dose
when the therapeutic conc of a drug in the plasma must be achieved rapidly
how do we calculate the loading dose
select the desired plasma conc of drug and multiply that by the Vd
after giving the loading dose how do we continue to administer the drug
at the maintenance dose rate to maintian the drug conc at the steady state
equation to calculate dose rate,
dose rate = Cl x desired drug plasma
whats the maintenance dose rate
the dose of a drug required per unti time ot maintain a steady state level in the plasma to sustain a therapeutic effect
how is dose rate expressed
mg/hour
what can ampicillin cause in horses
colitits
atorpine can cause what in horses
systemic side effects with local application
ivermectin effect in dogs
MDR1 gene, in 1/3 of collies and australian shepherds - ivermectin can lead to paralysis in sensitive animals
what can sulphonamides cause in dogs
idiosyncratic reactions
how can a fever affect drug action
reduced emptying of stomach, negative effect on absorption
how can diarrhoea affect drug action
increased gut motility, decr bioavaliability, exsiccation
how can gender affect drug action
in males metabolism could be faster, testosterone is a CYP3A inducer
altered physiology to do with absorption that can be seen in older animals
decr gastric acid secretion, incr gastric pH, decr GI blood flow, decr pancreatic trypsin, decr GI motility
clinical considerations of the altered physiology that can be seen in older animals
altered dissolution rate, possible decr absorption, time of onset delayed
altered physiology of body composition in older animals
decr in total body water, decr lean body wight and inc in body fat
clinical considerations on altered physiology of body composition in older animals
polar drugs tend to have decr Vd, while lipid-soluble drugs have incr Vd
altered physiology of protein binding of older animals
decr in serum albumin, incr in 1-GP, incr in gamma globulins, decr RBC binding
clinical considerations of altered physiology of protein binding
incr free fraction of acidic drugs, decr free fraction of basic drugs
altered physio of metabolism of older animals
decr enzyme induction, decr hepatic blood flow, decr hepatic mass, decr glucoronidation
clinical considerations of altered physio of metabolism of older animals
decr metabolism and clearance influenced by environmental factors
altered physio of excretion in older animals
decr GFR, decr renal plasma flow, decr active secretion
clinical considerations of altered physio of excretion in older animals
decr renal clearance, incr half life
how does tolerance influence a drugs action
subjects reaction to a drug decreases
whats habituation
force of habit, mental, not a real pyschological - weak drug dependancy
whats addiction
stong pyschological and frequently physiological drug dependancy
whats idiosyncrasy
individual hypersensitiveness, serious symptoms, hereditary eg doberman against phenylbutazone
whats an allergic reaction
an uncommon and unwanted side effect of medication, less than 10% of adverse effects are allergic
factors maintaining drug allergy are
contamination of skin, inhalation, depot preparations, chronic diseases, atropy
four types of allergic reactions
anaphylactic, cytolytic, immune-complex mediated, immune complex associated, delayed or cellular
immediate or anaphylactic reaction mechanism
IgE receptors of mass cells or basophile leucocytes and allergens
is the elimination of clinical signs fast in an anaphylactic reaction
yes
whats anaphylactoid reaction
a clinically similiar reaction to anaphylaxis but is not mediated by IgE, caused by an unknown mechanism
cytolytic reaction mechanism
IgG and IgM maintained, complement activation dependant
examples of cytolytic reactions
haemolytic anaemia, thrombocytopenia, cytolysis, interstitial nephritis, systemic lupus erythematosus
immune comlex associated reactions mechanism
immune complex formation, mainly IgG antigens
immune-complex associated reactions examples
serum sickness, urticaria, drug fever, some cutaneous eruptions, vasculitis
delayed or cellular reactions mechanism
T-lymphocytes and macropahges maintained hypersensitivity
delayed or cellular reactions examples
contact dermatitis, morbilliform eruptions
