DEFINITIONS T1/2 & Tmax Cmax AUC 1st order kinetics Zero order kinetics Steady state (enteric coated, longer T1/2) Loading doses Therapeutic index

Maximum plasma concentration achieved Amount of drugs in plasma = Bioavailability Time to maximum peak plasma concentration Area of plasma concentration to fall by half Only applies to drugs with first order kinetics

Distribution leads to a fall in plasma concentration / achieving equilibrium within different compartments. Vd=Q/C. When Vd is high = high affinity for lipophilic tissues seen in psychotropic drugs

1-Rate of elimination independent of the amount of drug present 2-e.g fixed IV infusions, alcohol, absorption from depot 3-There is no fixed half-life 1-Applies to most drugs 2-Rate of elimination depends of the amounts of the drug present 3-Amount of the drugs eliminated in each half-life differs

ELIMINATION Excretion by kidneys most important Li+: most important; What is the effect of Na+ Urinary pH: important for barbiturates Age Renal impairment Also through bile or through skin

Steady state: after repeated dosage leading to an equilibrium between absorption and elimination Depends on dose, time between dose and elimination half life Achieved after 4-5 half life Loading dosage can be given to achieve therapeutic plasma concentration Therapeutic Index: Is the minimum plasma drug concentration causing toxic effect to that causing therapeutic effect

PHARMACODYNAMICS Level of actions Examples Re-uptake Mechanism of action of drugs “The effect of the drug on the body” Usually there is a neurotransmitter or various involved. The therapeutic effect appears to depend on the neurotransmitter that is involved (also the Side effects) Effect can occur at various levels Level of actions Examples Re-uptake TCA, SSRI, Cocaine Pre synaptic Lofexidine at alpha 2 Post synaptic D2 blockers antipsychotics Partial agonist Aripiprazole / Buprenorphine antagonist Flumazenil Full agonist Bzd at GABA complex Second messenger Lithium at inositol level