مقدمة في الصيدلة - المحاضرة 4

Introduction to Pharmacy

• This is a course on pharmacy.
• The lecture number is four.

Pharmacokinetics

• Pharmacokinetics is the study of how the body affects drugs.
• It tracks the drug's journey from absorption to excretion.
• This is a key component of drug development.
• It explains the drug's biological properties and behavior in the human body, by studying the life cycle of the drug inside the body.
• Abbreviation ADME is used (Absorption, Distribution, Metabolism, Elimination).

Pharmacokinetic Methods

• Intravenous administration is a common method for studying drug kinetics.
• Determining drug elimination constant (ke), clearance, distribution, and half-life (t1/2) are examples of parameters tracked using intravenous administration.

Rate and Extent of Absorption

• Rate of absorption describes the speed of drug entry into the bloodstream.
• Extent of absorption represents the amount of drug reaching the bloodstream.
• The amount of absorption is a critical factor for determining whether the drug can be incorporated into different pharmaceutical forms (e.g., tablets, solutions, transdermal patches). and its ability to reach the general circulatory system to achieve the predicted pharmacological effect.

Bioavailability

• Bioavailability (BA) describes the drug reaching the systemic circulation.
• It is the fraction of administered drug that reaches the bloodstream.
• The rate of absorption (how quickly) and the extent of absorption (how much) are both assessed.
• BA is influenced by individual factors and pharmaceutical formulations.
• Comparisons are made to IV administration (if possible).

Graphical representation of Bioavailability

• The graph shows drug concentration vs. time.
• Two curves are presented; one for an IV injection and one for oral administration.
• The area under the curve (AUC) represents the total amount of drug reaching the systemic circulation.

Factors affecting Bioavailability

• Factors involved with the drug's physical/chemical properties influence bioavailability.
• Examples are solubility, stability, and molecular weight, and the use of excipients.
• Proper pharmaceutical formulation is important to maximize bioavailability.
• Patient-related factors like disease, food intake, and time of administration can influence bioavailability.

Absolute Bioavailability

• A comparison of AUC between oral and IV administration.

• The equation for calculating Absolute Bioavailability: F = (AUC_oral/AUC_IV) x (Dose_IV/Dose_oral)

Drug examples (Hippuric Acid ,Paracetamol, Montelukast)

• Provided examples of drugs and their pharmacokinetic properties (absorption, distribution, metabolism, and excretion).
• Data like Cmax (maximum plasma concentration), Tmax (time to maximum concentration), and half-life (t1/2) were listed for different drug examples.
• Clearance rate was mentioned.

Therapeutic Window

• The therapeutic window represents the range of drug concentrations that produce a therapeutic effect without causing toxicity.
• The minimum effective concentration (MEC) defines the lowest concentration needed for effectiveness.
• The minimum toxic concentration (MTC) defines the highest concentration that does not cause toxicity,
• Onset and duration are part of the graphical representation indicating when the drug starts and stops having effect.