D1 Flashcards
Definition of drugs
Chemicals that affect how the body works, for better or worse and does one or more of the following:
alters incoming sensory sensations
alters mood/emotions
alters physiological states
Definition of medicine
A substance that improves health - can be natural or synthetically made
Administering of drugs
Oral, inhalation, skin patches, suppositories, eye or ear drops, parenteral - injection
Injection: modes of administration
Subcutaneous - drug injected directly under the surface of the skin
Intravenous - drug injected directly into the blood stream
Intramuscular - drug injected into a muscle
Oral delivery
Consumption of the drug - generally via tablet, capsule, or syrup formulation
Most common delivery method for drugs
Advantages - convenient
Disadvantages - the drug molecule can be destroyed by stomach acid, long lag time, only small amount of the drug is absorbed, can cause stomach bleeding or vomiting, and patient needs to be conscious
Subcutaneous
Used where slow absorption is needed - slower effect
Effect of drug is experienced at a slower rate than intravenous but faster than intramuscular
Intravenous
Used for immediate impact - drug is immediately pumped around the body by blood
Can be used where delivery of drug is required for long period of time
Allows for very precise amount of drug to be delivered
Intramuscular
Many vaccines, antibiotics, anaphylactic treatment via EpiPen
Usually when large dose needs to be administered and needs to act locally
Large volumes of drug can be delivered safetly
Suppositories
Commonly used when oral administration is not possible due to extreme nausea or vomiting, febrile convulsions in children, following surgical procedures where patients ability to swallow has been compromised
administered by insertion of suppository into rectum where drug is absorbed by large intestine directly into blood stream
Faster therapeutic effect than oral administration
Laxatives, vasoconstrictors and/or moisturisers for treatment of haemorrhoids, analgesics
Inhalation
Active substance is delivered via inhalation of a fine powder or vapour directly into lungs
rapid absorption and action - drug passes directly from lungs into blood vessels
Used to treat respiratory illnesses like asthma and general anaesthesia
Bioavailability
Fraction of the administered dose that reaches blood stream
Influenced by mode of administration, solubility, functional groups
Intravenous has 100% bioavailability and is used as a basis for comparison
Dosage must consider bioavailability of drug
First pass effect
Only 20-405 of an orally ingested drug could reach blood stream
Orally administered drugs have relatively low bioavailability because enzymes found in stomach can chemically alter drug
Once absorbed from digestive system, drug passed into blood then to liver where further metabolic breakdown reactions occur
Oral drugs have dosage 4x amount of intravenously administered
Solubility
Lipid solubility helps in the passage of the drug through membranes during absorption
Water solubility is important for circulation in the aqueous solution in the blood
Morphine - more polar, less lipid soluble so is hard to pass across cell membrane of small intestine - administer intravenously
Codeine - less polar, more lipid soluble so is quite effective as oral administration
Functional groups
Affect the bioavailability of drug, especially acid-base groups
Pka and Pkb of groups in molecule will determine the charges carried on the drug at different pH values and therefore its reactivity and solubility in different parts of the body
Physiological effects
Drugs will react and interact differently for every person due to metabolism
Must consider side effects, tolerance and addiction, and dosage when prescribing medication
Side effects
Physiological effects of drug in body can be classified as therapeutic effect - intended physiological effect, and side-effects - unintended physiological effects
Tolerance and addiction
If specific dose of a drug is given to a person repeatedly a tolerance can develop - reduced response can occur so higher doses may need to be administered
Patient may become addicted/dependent on drug as by taking it they feel normal and suffer withdrawal symptoms if not taken
Dosage
Must take bioavailability into consideration as well as age, weight, sex, diet, environment, interaction with other drugs the patient is already taken
Must keep levels of drug within the therapeutic window
Therapeutic index
The ratio of the dose that produces toxicity to the dose that produces a clinically effective response in population
Humans: TI = TD50/ED50
Animals: TI = LD50/ED50
Higher the TI, wider the margin between doses that are effective and doses that are toxic - safer
Low TI = low margin of safety
Placebo effect
Occurs when a person experiences a positive therapeutic experience because they have been given a medicine however this is a placebo - human body fooled into healing itself naturally
Used as a control to measure the real effectiveness of the drug which is the difference between the effects experienced by patients who took drug and those that did not
Drug-receptor interactions based on drug structure and site of activity
Activity of drugs determined by their ability to bind to particular receptors in the body
Normal biological activity inhibited when drug binds to receptor - interaction between drug and receptor depends on chemical fit between them: better fit = greater effect
Binds via non-covalent bonds
Development of drugs
- Identification and selection of disease
- Identification of pharmacological target
- Identify a lead molecule candidate
- Preclinical trials (in vitro)
- Clinical trials (in vivo)
- Reporting of trial results to regulatory bodies
- Monitoring of drug after market release
In vitro testing
Lead molecule tested on human/animal cells and tissues which have been removed from body and kept in an artificial environment
Used to look at efficacy, initial concentrations, cellular uptake
In vivo testing
Drug tested on animals - regulations vary between countries and remain highly ethical charged issue
Broad form of testing used to determine effective doses and potential side effects
Usually testing in 3 different species
