Assignment
on
Pharmacists and Biopharmaceutics
Course Code: PHAR 3207
Course Tittle: Biopharmaceutics and Pharmacokinetics I
Pharmacists and Biopharmaceuitics
Pharmacists
A pharmacist (also known as a chemist) is a healthcare professional who specializes in the preparation, dispensing, and management of medications and who provides pharmaceutical advice and guidance. Pharmacists often serve as primary care providers in the community, and may offer other services such as health screenings and immunizations.
Pharmacists undergo university or graduate-level education to understand the biochemical mechanisms and actions of drugs, drug uses, therapeutic roles, side effects, potential drug interactions, and monitoring parameters. This is mated to anatomy, physiology, and pathophysiology. Pharmacists interpret and communicate this specialized knowledge to patients, physicians, and other health care providers.
Among other licensing requirements, different countries require pharmacists to hold either a Bachelor of Pharmacy, Master of Pharmacy, or a Doctor of Pharmacy degree.
The most common pharmacist positions are that of a community pharmacist (also referred to as a retail pharmacist, first-line pharmacist or dispensing chemist), or a hospital pharmacist, where they instruct and counsel on the proper use and adverse effects of medically prescribed drugs and medicines. In most countries, the profession is subject to professional regulation. Depending on the legal scope of practice, pharmacists may contribute to prescribing (also referred to as "pharmacist prescriber") and administering certain medications (e.g., immunizations) in some jurisdictions. Pharmacists may also practice in a variety of other settings, including industry, wholesaling, research, academia, formulary management, military, and government.
Roles of a Pharmacist
Pharmacists are often the first point-of-contact for patients with health inquiries. Thus pharmacists have a significant role in assessing medication management in patients, and in referring patients to physicians. These roles may include, but are not limited to:
clinical medication management, including reviewing and monitoring of medication regimens
assessment of patients with undiagnosed or diagnosed conditions, and ascertaining clinical medication management needs
specialized monitoring of disease states, such as dosing drugs in kidney and liver failure
compounding medicines
providing pharmaceutical information
providing patients with health monitoring and advice, including advice and treatment of common ailments and disease states
supervising pharmacy technicians and other staff
oversight of dispensing medicines on prescription
provision of and counseling about non-prescription or over-the-counter drugs
education and counseling for patients and other health care providers on optimal use of medicines (e.g., proper use, avoidance of overmedication)
referrals to other health professionals if necessary
pharmacokinetic evaluation
promoting public health by administering immunizations
constructing drug formularies
designing clinical trials for drug development
working with federal, state, or local regulatory agencies to develop safe drug policies
ensuring correctness of all medication labels including auxiliary labels
member of inter-professional care team for critical care patients
symptom assessment leading to medication provision and lifestyle advice for community-based health concerns (e.g. head colds, or smoking cessation)
staged dosing supply (e.g. opioid substitution therapy)
Introduction to Biopharmaceutics
Biopharmaceutics: Biopharmaceutics is defined as the study of factors influencing the rate and amount of drug that reaches the systemic circulation and the use of this information to optimize the therapeutic efficacy of the drug prod- ucts.
Absorption: The process of movement of drug from its site of administration to the systemic circulation is called as absorption.
Bioavailability: Bioavailability is defined as the rate and extent (amount) of drug absorption.
Distribution: The movement of drug between one compartment and the other (generally blood and the ex-travascular tissues) is referred to as drug distribution.
Elimination: Elimination is defined as the process that tends to remove the drug from the body and terminate its action. Elimination occurs by two processes biotransformation (metabolism), which usually inactivates the drug, and excretion which is responsible for the exit of drug/metabolites from the body.
Pharmacokinetics: Pharmacokinetics is defined as the study of time course of drug ADME(Adsorption, Distribution, Metabolism, Excretion) and their relationship with its therapeutic and toxic effects of the drug. Simply speaking, pharmacokinetics is the kinetics of ADME or KADME.
Clinical pharmacokinetics: The use of pharmacokinetic principles in optimizing
the drug dosage to suit individual patient needs and achieving maximum therapeutic utility is called as clinical pharmacokinetics.
Drug administration and therapy can now be conveniently divided into four phases or processes:
1. The Pharmaceutic Process: It is concerned with the formulation of an effective dosage form of the drug for administration by a suitable route.
2. The Pharmacokinetic Process: It is concerned with the ADME of drugs as elicited by the plasma drug concentration-time profile and its relationship with the dose, dosage form and frequency and route of ad- ministration. In short, it is the sum of all the processes inflicted by the body on the drug.
3. The Pharmacodynamic Process: It is concerned with the biochemical and physiologic effects of the drug and its mechanism of action. It is characterized by the concentration of drug at the site of action and its relation to the magnitude of effects observed. Simply speaking. pharmacodynamics deals with what the drug does to the body in contrast to pharmacokinetics which is a study of what the body does to the drug.
4. The Therapeutic Process: It is concerned with the translation of pharmacologic effect into clinical benefit.
Toxicokinetics: Toxicokinetics refers to the study of absorption, distribution, metabolism/biotransformation, and excretion (ADME) of toxicants/xenobiotics in relation to time.
It is an application of pharmacokinetics to determine the relationship between the systemic exposure of a compound and its toxicity. It is used primarily for establishing relationships between exposures in toxicology experiments in animals and the corresponding exposures in humans. However, it can also be used in environmental risk assessments in order to determine the potential effects of releasing chemicals into the environment. In order to quantify toxic effects, toxicokinetics can be combined with toxicodynamics. Such toxicokinetic-toxicodynamic (TKTD) models are used in ecotoxicology.
Similarly, physiological toxicokinetic models are physiological pharmacokinetic models developed to describe and predict the behavior of a toxicant in an animal body; for example, what parts (compartments) of the body a chemical may tend to enter (e.g. fat, liver, spleen, etc.), and whether or not the chemical is expected to be metabolized or excreted and at what rate.
Pharmacodynamics: Pharmacodynamics is the branch of pharmacology, concerned with the effect of drugs and mechanism of their actions.
Applications of Biopharmaceutics
To predict in vivo performance of drug product using solubility and permeability measurements.
Aid in earliest stages of drug discovery research.
For research scientist to decide upon which drug delivery technology to follow or develop.
Also for the regulation of bioequivalence of the drug product during scale up and post approval.
Drug Development
Formulation Development
Deciding Dosage Regimen
Designing Rational Dose, Frequency and Duration
Rational Drug Design
Clinical Pharmacy
ADME study, Bioavailability and Bioequivalence studies
Pharmacokinetics, Pharmacodynamics Relationship
Plasma Drug Concentration-Time Profile
A direct relationship exists between the concentration of drug at the biophase (site of action) and the concentration of drug in plasma. A typical plasma drug concentration-time curve obtained after a single oral dose of a drug and showing various pharınacokinetic and pharmacodynamic parameters is depicted in Figure. Such a profile can be obtained by measuring the concentration of drug in plasma samples taken at various intervals of time after administration of a dosage form and plotting the concentration of drug in plasma (Y-axis) versus the corresponding time at which the plasma sample was collected (X-axis).
Figure:A typical plasma concentration-time profile showing pharmacokinetic and pharmacodynamic parameters. obtained after oral administration of single dose of a drug.
The three important pharmacokinetic parameters that describe the plasma level-time curve and useful in assessing the bioavailability of a drug from its formulation are:
1. Peak Plasma Concentration (Cmax)
The point of maximum concentration of drug in plasma is called as the peak and the concentration of drug at peak is known as peak plasma concentration. It is also called as peak height concentration and maxi- mum drug concentration. Cmax is expressed in mcg/mL. The peak level depends upon the administered dose and rate of absorption and elimination. The peak represents the point of time when absorption rate equals elimination rate of drug. The portion of curve to the left of peak represents absorption phase i.e. when the rate of absorption is greater than the rate of elimination. The section of curve to the right of peak generally represents elimination phase i.e. when the rate of elimination exceeds rate of absorption. Peak concentration is often related to the intensity of pharmacologic response and should ideally be above mini- mum effective concentration (MEC) but less than the maximum safe concentration (MSC).
2. Time of Peak Concentration (tmax)
The time for drug to reach peak concentration in plasma (after ex- travascular administration) is called as the time of peak concentration. It is expressed in hours and is useful in estimating the rate of absorption. Onset time and onset of action are dependent upon tmax. The parameter is of particular importance in assessing the efficacy of drugs used to treat acute conditions like pain and insomnia which can be treated by a single dose.
3. Area Under the Curve (AUC)
It represents the total integrated area under the plasma level-time profile and expresses the total amount of drug that comes into the sys- temic circulation after its administration. AUC is expressed in mcg/ml. X hours. It is the most important parameter in evaluating the bioavailability of a drug from its dosage form as it represents the extent of absorption. AUC is also important for drugs that are administered repetitively for the treatment of chronic conditions like asthma or epilepsy.
The various pharmacodynamic parameters are:
1. Minimum Effective Concentration (MEC)
It is defined as the minimum concentration of drug in plasma required to produce the therapeutic effect. It reflects the minimum concentration of drug at the receptor site to elicit the desired pharmacologic response. The concentration of drug below MEC is said to be in the subtherapeutic level.
In case of antibiotics, the term minimum inhibitory concentration (MIC) is used. It describes the minimum concentration of antibiotic in plasma required to kill or inhibit the growth of microorganisms.
2. Maximum Safe Concentration (MSC)
Also called as minimum toxic concentration (MTC), it is the con- centration of drug in plasma above which adverse or unwanted effects are precipitated. Concentration of drug above MSC is said to be in the toxic level.
3. Onset of Action
The beginning of pharmacologic response is called as onset of action It occurs when the plasma drug concentration just exceeds the required MEC.
4. Onset Time
It is the time required for the drug to start producing pharmacologic response. It corresponds to the time for the plasma concentration to reach MEC after administration of drug.
5. Duration of Action
The time period for which the plasma concentration of drug remains above the MEC level is called as duration of drug action.
6. Intensity of Action
It is the maximum pharmacologic response produced by the peak plasma concentration of drug. It is also called as peak response.
7. Therapeutic Range
The drug concentration between MEC and MSC represents the thera- peutic range.
Rate, Rate Constants and Orders of Reactions
Pharmacokinetics is the mathematical analysis of processes of ADME. The movement of drug molecules from the site of application to the systemic circulation, through various barriers, their conversion into an- other chemical form and finally their exit out of the body can be expressed mathematically by the rate at which they proceed, the order of such processes and the rate constants.
The velocity with which a reaction or a process occurs is called as its rate.
The manner in which the concentration of drug (or reactants) influence the rate of reaction or process is called as the order of reaction or order of process. There are different order of reaction:
Zero-order Kinetics (Constant Rate Processes)
First order Kinetics (Linear Kinetics)
Mixed order Kinetics (Nonlinear Kinetics)
Relationship between Pharmacists and Biopharmaceuitics
Pharmacists and biopharmaceutics have a close relationship within the broader field of pharmacy. Biopharmaceutics focuses on the study of how the physicochemical properties of drugs, their formulation, and route of administration influence their pharmacokinetic and pharmacodynamic behavior in the body.
Pharmacists use knowledge from biopharmaceutics to ensure the effective and safe delivery of medications to patients. They apply principles of biopharmaceutics to optimize drug formulations, dosage regimens, and routes of administration based on individual patient needs. Additionally, understanding biopharmaceutics helps pharmacists interpret drug interactions, absorption rates, bioavailability, and other factors crucial for therapeutic outcomes.
The relationship between pharmacists and biopharmaceutics is multifaceted and pivotal in the realm of pharmacy practice. Here are some detailed aspects of their relationship:
Drug Formulation and Development: Biopharmaceutics provides insights into how different formulations affect drug absorption, distribution, metabolism, and excretion (ADME). Pharmacists use this knowledge when working in pharmaceutical industries or compounding pharmacies to develop, modify, or recommend specific drug formulations based on patient needs.
Bioavailability and Bioequivalence: Biopharmaceutics examines factors influencing drug bioavailability (the rate and extent of drug absorption). Pharmacists consider bioequivalence studies when evaluating generic drug products, ensuring they deliver the same therapeutic effect as their brand-name counterparts.
Optimizing Drug Therapy: Pharmacists use biopharmaceutical principles to tailor drug therapy. They consider factors like drug solubility, stability, and absorption rates to select appropriate dosage forms and administration routes for patients, maximizing therapeutic outcomes.
Pharmacokinetic Analysis: Understanding biopharmaceutics aids pharmacists in interpreting pharmacokinetic parameters such as half-life, clearance, and volume of distribution. This knowledge is crucial for dose adjustments, monitoring drug levels, and minimizing adverse effects.
Clinical Decision-Making: In clinical settings, pharmacists utilize biopharmaceutics to make evidence-based decisions. They assess drug-drug or drug-food interactions, evaluate the impact of physiological changes (e.g., renal or hepatic impairment) on drug pharmacokinetics, and adjust therapy accordingly.
Patient Education: Pharmacists educate patients on medication use, emphasizing the importance of adherence, timing, and potential interactions. Biopharmaceutics knowledge enables pharmacists to explain complex concepts in understandable terms, empowering patients to manage their medications effectively.
Research and Innovation: Pharmacists engaged in research or academia leverage biopharmaceutics to advance drug delivery systems, study novel formulations, or explore personalized medicine approaches. This collaboration drives innovation in pharmacy practice, enhancing patient care outcomes.
Drug properties: Biopharmaceutics delves into the physical and chemical properties of drugs, like solubility, dissolution rate, and pKa. Pharmacists leverage this knowledge to understand how these properties affect a drug's absorption, distribution, metabolism, and excretion (ADME), ultimately influencing its efficacy and safety.
Dosage form design: Biopharmaceutics principles guide the design of effective dosage forms like tablets, capsules, or injectables. Pharmacists, informed by these principles, can make recommendations on the most appropriate form for a patient based on their needs and the drug's characteristics.
Drug interactions: Biopharmaceutics sheds light on potential interactions between drugs, which can alter their ADME and cause adverse effects. Pharmacists, armed with this knowledge, can identify and prevent such interactions when managing a patient's medication regimen.
Individualized therapy: Biopharmaceutics allows for tailoring drug therapy to individual patients. Pharmacists can consider factors like age, genetics, and disease state to adjust dosage or recommend alternative drugs based on their biopharmaceutical properties.
Clinical data collection: Pharmacists observe drug efficacy and side effects firsthand through patient interactions. This real-world data provides valuable feedback for biopharmaceutic research, informing the development of better and safer drugs.
Medication adherence: Pharmacists play a crucial role in educating patients about proper medication use, promoting adherence to prescribed regimens. This ensures optimal drug activity, leading to better treatment outcomes and contributing to biopharmaceutical data on drug performance.
Drug safety monitoring: Pharmacists are often the first to identify adverse drug reactions. Reporting these events to regulatory bodies like the FDA helps improve biopharmaceutical understanding of drug safety profiles and potentially leads to safer drug formulations.
In summary, pharmacists utilize biopharmaceutics principles to make informed decisions about drug therapy, ensuring that patients receive the right medication in the most effective and safe manner.
References
Biopharmaceutics and Pharmacokinetics-A Treatise By D.M. BRAHMANKAR & SUNIL B. JAISWAL
Biopharmaceutics & Clinical Pharmacokinetics: Milo Gibaldi
Biopharmaceutics & Clinical Pharmacokinetics: Notari, R. E
Biopharmaceutics & Relevant Pharmacokinetics: T. G. Wagner and M. Pernarowski
Biopharmaceutics & Drug Interactions: Donald E. Cadwallader
Pharmacokinetics: M. Gibaldi & D. Perrier.
Internet Sources: https://en.m.wikipedia.org/wiki/English_Wikipedia; https://www.britannica.com/; https://www.who.int/; www.sciencedirect.com;
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