Drug 1

• drug

  a substance that when introduced to the body produces a biological effect for an intended purpose
• what are drugs used for, and the exception

  to treat symptoms of condition, not the cause of disease (exception is antimicrobial drugs) or to prevent a condition (anti-HIV drugs to reduce risk)
• antimicrobial drugs 


  target the cause of infection rather than symtoms
• what are the 2 broad groups of drugs

  small molecules and biologics
• small molecules administration 


  orally e.g paracetamol
• biologics administration 


  to big to orally, subcutaneously administer e.g AA peptides
• types of drug name

  chemical, generic, brand/trade name
• chemical name


  for chemists, describes the chemical structure of drug
• generic name


  for pharmacologists, stems/roots to indicate origins, use, action or structure of drugs
• brand/trade name


  for general public, invented by drug companies for marketing purpose, different depending on manufacturer and country
• PK


  pharmacokinetics, what the body does to a drug
• 4 key principles of PK

  Absorption, distribution, metabolism, excretion
• major PK associated organs


  intestine, liver, kidneys
• organs with barrier function

  brain, placenta
• brain transporters function


  barrier, influx transporters expressed at barrier to remove drugs to don't cause harm
• placenta transporters function


  minimise harmful toxins and protect developing foetus
• what plasma-cone time curve tells us


  dose, frequency of drug administration, drug toxicity
• 2 routes of administration

  most common oral administration or intravenous
• Cmax


  peak plasma concentration
• Tmax


  time required to achieve Cmax
• therapeutic window


  a concentration range bound by MEC lower end and MTC at upper end
• Minimum toxic concentration (MTC)


  concentration that produces unacceptable effects or where no further benefit observed
• minimum effective concentration (MEC)


  minimum for drug to produce desired effects
• duration of action of drug

  time when concentration is in therapeutic window
• AUC of drug 


  gives idea of total exposure of body to drug
• drug absorption


  process by which a drug moves from its site of administration to systemic circulation
• body compartmentalisation


  drugs need to cross lipid membrane to move from one compartment to another, depends on physical and chemical components of the drug
• 2 mechanisms for drugs moving across membrane

  transcellular (move across cell) and paracellular (through tight junctions)
• drugs that move across cell membrane and how

  lipophilic drugs via passive or facilitated diffusion (carrier proteins)
• drugs that move through tight junctions

  low molecular weight and hydrophilic drugs
• physicochemical properties of drug that affect oral absorption

  molecular size, solubility, ionisation
• how molecular size effects oral absorption

  decreases as molecular weight increase (to large can't)
• how solubility affect oral absorption


  hydrophilicity and lipophilicity affect passive diffusion at membrane
• very lipophilic drugs 


  get stuck in cell lipid membrane and distributed into adipose tissue
• lipophilic drugs absorption

  can cross membrane, reach other side of blood brain barrier
• how ionisation effect drug absorption


  if ionised molecule cant cross lipid membrane passively, move compartments. degree of ionisation changes depending on pH environment
• ionisation of drugs


  many drugs classed as weak acids/bases results in pH dependent ionisation of functional groups
• pKa 


  pH at which drug molecules are 50% ionised
• biological factors that affect oral absorption


  pH, ingested food, gut mobility (fat/protein slow down absorption decrease conc in blood), intestinal enzymes, transporters
• activated charcoal 


  orally administered, has holes on surface that bind drug molecule then molecules are not absorbed and removed in faeces. given if early detection of drug overdose