Pneumonia Flashcards
Define the terms clearance (CL), half-life (t), volume of distribution (V)
Clearance - volume of plasma cleared of a drug in unit time
Half-life - the amount of time it takes for a drug concentration to decrease by half
Volume of distribution - the apparent volume in which a drug is dissolved in the body
Calculate V from a plot of log (plasma level) versus time.
Vd = amount in the body/concentration = dose/concentation at t=0
State that CL Clrenal Clhepatic, and be able to predict the consequence of change in either component on the plasma drug concentrations.
Clearance = clRenal + clHeapatic
State that at steady state Administration Rate Elimination Rate.
The steady state (Css, which is concentration steady state) is where the administration rate is equal to the elimination rate. Administration of a drug at a constant rate is a zero order process. Elimination is a first order process.
State the relationship between rate of drug infusion and steady state blood level.
Infusion Rate = Clearance x Concentration Steady State
Identify the pharmacokinetic parameters that are used to describe the rate and extent of drug absorption from an oral dose.
- rapid-release formulation, the rise to the peak is extremely quick.
- sustained release formulation, there is a prolonged absorption superimposed on elimination and the half-life is not a true elimination half-life and is known as ‘context-sensitive half-life’ or ‘functional half-life’.
Define the term bioavailability (F), state the use of AUC values to calculate F.
F - the fraction of a drug absorbed
F = (AUCoral)/(AUCiv)
Identify the factors that determine the time to steady state, the steady state concentration, and the fluctuations around this concentration on repeat dosing of a drug.
dose interval, bioavailability, clearance
Identify three factors of importance when designing a dosage regimen.
In a short half-life drug (usually around one hour) with a wide therapeutic window, it is given three to four times per day. A drug with a short half-life with a narrow therapeutic window, intravenous infusion is used.
Define a loading dose and a maintenance dose and define what pharmacokinetic parameters are required to set these values for an individual drug.
Loading Dose = (Target Steady Sate x Volume Distribution)/Bioavailability.
Maintenance Dose = (Target Steady State x Clearance x Tau)/Bioavailability
The maintenance dose for drugs with a long half life is the amount eliminated per day as a daily dosing regimen is optimal for patient compliance.
Describe the principles of antimicrobial chemotherapy
antimicrobial chemotherpay is the use of drugs to selectively kill bacteria (and viruses / fungi) without affecting the host. The targets are the bacterial cell wall, bacterial ribosomes, bacterial folate metabolism, bacterial DNA gyrases. Antibiotics are produced by an organism to attack other organisms. Antibacterials are also used and are usually man-made.
Be able to describe the mechanisms of action of: 1)Beta-lactam antibiotics 2)Macrolides 3)Tetracyclines 4)Folate inhibitors 5)Quinolones 6) Aminoglycosides
Beta-lactams: target bacterial cell wall synthesis by binding irreversibly to a transpeptidase which cross-links peptidoglycans in the bacterial cell wall.
Macrolides: Macrolides prevent the translocation of the 50S subunit of the bacterial ribosome along the mRNA. This prevents protein synthesis.
Tetracyclines: inhibit protein synthesis by binding to the 30S subunit of the bacterial ribosome and prevents tRNA from binding at the acceptor (A) site.
Folate Inhibitors: inhibits the bacterial dihydrofolate reductase, which converts folate to tetrahydrofolate. It is less potent against the human form of the enzymes needed to form DNA.
Quinolones: These are inhibitors of bacterial DNA gyrase and topoisomerase IV. In gram negative bacteria, DNA gyrase is inhibited and quinolone inhibits the supercoiling of the bacterial DNA, which is essential for DNA repair and replication. In gram positive bacteria, topoisomerase IV is the target and quinolones interfere with the separation of DNA strands on replication. They are bactericidal.
Aminoglycosides: These bind irreversibly to the 30S subunit of bacterial ribosomes, leading to misreading of mRNA and interfere with protein synthesis.
Define the terms patient safety, incidents and error.
Patient safety - the freedom for patients from unnecessary or potential harm arising from health care.
Patient safety incident - any unintended or unexpected incident which could have or did lead to harm for one or more patients receiving NHS funded care.
Human error - occurs when the actions and decisions of individuals result in failures that can immediately or directly impact patient safety.
Outline the key components of a high quality healthcare organisation.
Quality care is safe, effective, timely, efficient, person-centered and equal. Safe is minimising incidents and harm, mitigating risk, continuously improving, being just and proportionate, being open and honest, supporting those in incidents and having the freedom to speak up.
Describe the main pattern of lung infection by M. tuberculosis
- grows in tissues with a high oxygen content.
- usually infectis mononuclear phagocytes.
- slow-growing and hydrophobic due a high lipid content in the cell wall. - less permeable to usual bacterial stains
