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17 Cards in this Set
- Front
- Back
What is Pharmaceutics?
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the
formulation (design), manufacture (fabrication), stability (expiration), and effectiveness (evaluation) of pharmaceutical dosage forms or drug delivery systems |
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What is a dosage form?
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Dosage form provides a mechanism for the convenient and safe delivery of the accurate and precise dose of a given drug substance
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Why Do Patients Need a Dosage Form?
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A dosage form or drug delivery system provides a
mechanism for convenient and safe delivery of the correct dosage of the drug . Protection of a drug substance from oxygen and humidity - coated tablets and sealed ampules with an inert gas like nitrogen. 2. Protection of a drug substance from influence of gastric acid after oral administration - enteric coated tablets. 3. Concealing the bitter, salty, or offensive taste or odor of a drug substance - capsules and tablets 4. Providing liquid preparations of drugs that are unstable or insoluble in the desired vehicle (solvent) - suspensions (for reconstitution). 5. Providing rate and time-controlled drug action (modified) - sustained or delayed release tablets. 6. Providing optimal drug action from novel dosage from such as topical administration and inhalation therapy. 7. Instantaneous delivery of drug directly into the blood circulation (invasive) - IV bolus and infusion. |
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Factors that Considered Before a Drug Is Formulated Into One or More Dosage Forms
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Nature of the illness: motion sickness - preventive tablet/patch or therapeutic suppository (scopolamine)
Manner in which it is treated: topical (creams or lotions) or systemic (tablets and injections) Likely age of the patient: pediatric and geriatric Anticipated condition of the patient: comatose or ambulatory Stability of the drug: powder for reconstitution (suspension) |
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What Would be the Characteristics of An Ideal Drug Delivery System?
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An Ideal Drug Delivery System should itself be stable and withstand a stable surrounding:
Physical Stability - prevent polymorphic changes, amorphous-crystalline transitions, prevents light induced degradation (Intro course) Chemical Stability - against oxidation, hydrolysis (atmospheric moisture, oxygen) Microbiological Stability - preserve the drug against microbial spoilage Provides unit dose precision and Ensures consistent bioavailability e.g.,Procardia XL® Provides special release characteristics: enteric coating - releases the drug in the intestine to avoid degradation of acid sensitive drug provides controlled release for optimum therapy - e.g. sustained release tablets Improves patient compliance - patients feel easy and relaxed Convenience - convenient to consume, carry and store Aesthetics - presents a professional appearance/ pharmaceutical elegant Improve organoleptic qualities - mask the offensive odor/ taste of the drug e.g. Glucophage and Citrical |
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What Factors Lead to the Selection of a Given Dosage Form?
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Physical, chemical, and biological stability
Organoleptic characteristics of the drug Nature of illness e.g. coma, seriousness of the illness, nausea & vomiting Age of the Patient e.g. elderly and pediatric patients population Bioavailability (amount of drug available at action or receptor site) considerations |
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A slight variation in the dosage form and in the
routes of administrations can result in |
different
profiles of absorption rate, times of onset, peak and duration of action |
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Per Oral (po) Route (Most Frequent: advantages and disadvantages?
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mouth, gets into GIT
(Gastrointestinal tract) via mouth, mainly for systemic use, some times local action Advantages: most natural, uncomplicated, convenient, safe method, a wide range of pH available for absorption of various drugs (acidic and basic drugs) through GIT Disadvantages: slow drug response, chances for irregular absorption, degradation of certain drugs due to stomach acid, intestinal enzymes etc. Dosage Forms: tablets, capsules, solutions, syrups, elixirs, suspensions, emulsions, etc. Note: Solutions are absorbed faster than any other dosage form. Suspensions, capsules, tablets must undergo dissolution before absorption. Tablets are the slowest absorbed, because they must undergo disintegration prior |
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Sublingual and Rectal Routes
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Site: beneath the tongue only
systemic Advantages: quick onset of action, escapes first pass effect Disadvantages: inconvenient, taste, small dose etc. Dosage Forms: tablet Site: rectum mainly local (soothing of inflamed tissues) some times systemic Advantages: may escape first pass effect, useful in infant, elderly, comatose and uncooperative patients, escapes acid degradation of stomach Disadvantages: inconvenient, chances of irregular absorption Dosage Forms: solutions, ointments, suppositories e.g. |
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Parenteral (Other Than the Intestines), Topical and Transdermal Routes
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Site: other than GIT (by injection),
only systemic Primary Routes: subcutaneous, intramuscular, and intravenous Advantages: rapid predictable absorption, can deliver drugs that are poorly absorbed from GI tract or degraded in GI tract, escapes first pass effect, useful in infant, elderly, comatose and uncooperative patients Disadvantages: more expensive, no retrieval, requires trained personnel (IV nurses) Dosage Forms: sterile solutions and suspensions e.g., Humalog Pen® (in diabetes) Site: skin surface, local action Advantages: convenient, can be removed, local action Disadvantages: can be messy Dosage Forms: powders, ointments, pastes, creams, lotions, sprays Site: skin surface, systemic delivery Advantages: convenient, can be removed, escapes first pass effect, slow continuous delivery of drug Disadvantages: expensive, only low mol. wt. drugs with high partition coefficient (Ka) are suitable for transdermal formulations Dosage Forms: Transdermal patches discs, iontophoretic, sonophoresis techniques and more e.g. Hydrocortisone® (as cream and ointment) and Orthro-Evra® Patch (menopause- hormonal disbalance) |
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What happens to a Drug after it is Administered to a Patient?
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After administration (mostly orally or other routes),
a drug substance gets absorbed through a membrane(s) or if administered instantaneously as IV (intravenous) gets directly into the systemic circulation (blood) Then the absorbed drug substance gets into the blood and tissues and distributed throughout the body tissues and fluids Afterwards absorbed drug substance is metabolized in the liver and passed out (excreted) the body system through different channel mainly kidneys |
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Bioavailability?
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Bioavailability: The rate and extent to which a drug
substance is absorbed from a drug product (a dosage form) and becomes available at absorption site of drug action The following oral dosage forms are ranked here based on their bioavailability from fastest to slowest: Fastest Availability Solutions Suspensions Capsules Tablets Coated Tablets Slowest Availability Controlled Release Formulations (slow release or modified release) |
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Bioavailable Fraction (F)
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The fraction of administered dose, that actually gets into the
BLOOD (systemic circulation) as intact (unchanged) drug to produce clinical effect (drug action). - unitless (a fraction term |
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What are some reasons for F<1?
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1. Poor solubility and incomplete dissolution
2. The drug is not completely absorbed through the gastrointestinal tract (GIT- ABSORPTION: is the extent to which intact drug is absorbed from the gut lumen into the portal-systemic circulation). 3. Decomposition in the intestines 4. The drug is transformed in the intestine to a metabolite* 5. The drug is metabolized or eliminated by the liver: is the extent to which a drug is removed by the liver during its first passage through the liver after absorption prior to reaching the systemic circulation (blood). This is also called first-pass metabolism or first-pass effect. |
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What are Some Extravascular Routes of Administration?
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Extravascular routes are:
buccal per oral (PO) per rectal (PR)-Superior hemorrhoidal vein intramuscular (IM) subcutaneous (SC OR SQ) sublingual (SL) transdermal (TD) |
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First Pass Effect (or first pass metabolism)
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The blood draining those sites (PO and PR) happens to
flow directly through the liver BEFORE getting to the general (systemic) circulation |
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Non-First Pass Routes
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The blood draining those sites (buccal, intramuscular,
subcutaneous, sublingual, transdermal) flows directly to the general circulation first, not the liver The liver removes no portion of the drug before reaching general circulation |