Lecture 1: Introduction to Pharmacology Flashcards
Pharmacology is?
The study of actions, mechanisms, uses and adverse effects of drugs.
What is a therapeutic index?
The window between the amount of drug required to produce effects and the amount that will cause harm to a patient.
What are the requirements of a drug?
- Selective (specific, limited s/e, low toxicity)
- Active at low concentrations
- Reversible
- eliminated from body
- Effective
- Safe
What do pre-clinical trials consist of?
Pre-clinical trials are dedicated to analysing to chemistry of drugs to discover more selective drugs. Using cell culture assays, and progressing to animal studies, these drugs are tested for their:
- Toxicity
- Absorption into blood
- Where in the body the drug takes effect
- How drug is eliminated
- Formation (form of drug, what it is mixed with)
- Route of administration
- etc.
How many stages are there in clinical trials of a drug?
There are 4 phases.
Phase 1 - drug is tested on healthy volunteers to assess safety of drug and any s/e - about a few months
Phase 2 - Tested on small group of patients with the ailment to test for right dosage to treat targeted disease. There will be placebo group - about 2 years
Phase 3 - Tested on 100s of people, to determine if a drug is safe for use on a large diverse population. There will be treatment or control groups with placebo. - around 5-10 years
Phase 4 - Long term testing on effects over the course of time it is legal and prescribed, monitoring phase.
What 4 factors should be considered before a drug is prescribed?
- Has there been an accurate diagnosis?
- Acknowledge drug effects as they may be powerful
- Review of the drug history of patient
- What are the implications of the prescription?
What is pharmacokinetics?
The branch of pharmacology dedicated to the metabolic interactions and the fate of drugs in the body, and the rate of these processes.
What are the 4 stages of pharmacokinetics?
ADME: Absorption Distribution Metabolism Excretion
What is absorption in pharmacokinetics?
The process of drug movement from site of administration towards the bloodstream. Drugs that are injected no need for absorption. There are different methods of absorption into the body: - Oral - Rectal - Intravenous - Intramuscular - Sub-cutaneous - Inhaled
What affects drug absorption?
Formulation - Other ingredients accompanying the drug, form of drug.
Gut motility/Disease - Diarrhoea causing illnesses can mean drugs pass through body faster without being absorbed.
Empty stomach/full stomach - Can change pH and other factors
Stability of drug to acid and enzymes
What is drug distribution in pharmacokinetics?
The disbursement of unmetabolized drug as it moves through the body.
Volume of distribution means what?
The amount of drug that has moved from the blood into the tissues.
Calculated by dividing the dose given by the plasma concentration of drug.
How can lipid solubility affect rate of drug absorption? Compare this to how water soluble drugs behave in the body.
Lipid soluble drugs will migrate and stay in fat tissue and take longer to leave and enter the rest of the body, water soluble drugs will not do this, staying in the blood and interstitial fluid to then be excreted. Lipid soluble drugs can move through membranes faster than water soluble drugs, which may rely on transport mechanisms.
How can plasma protein binding affect drug performance?
Drug performance is affected by plasma protein binding because if a drug highly binds to plasma proteins then less of it will enter body tissues where they produce an effect.
In certain groups of people plasma protein concentration can vary and so this can factor into a drugs performance and thus must be considered when prescribing drug.
Only unbound drugs can leave the vascular system, exert their pharmacological effects and get excreted and metabolised
What factors affect plasma protein binding?
Different plasma proteins bind to drugs based on it’s acidity, acidic drugs like aspirin will bind to albumin.
Drugs will have affinity for binding sites on a protein. (Higher the affinity, the more drugs binding).
Temperature can affect how strongly drugs bind.
Age, as older people generally have fewer plasma proteins and therefore will need lower doses.
Illnesses can affect protein concentration, an example is liver disease, as albumin is made in the liver.
