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Pharm lecture 2
Introduction to drug use and principles: how and when do drugs work
| Question | Answer |
|---|---|
| What is a drug? | Pharm def: chemical substance used in the treatment, cure, prevention, or diagnosis of a disease or used to otherwise enhance physical or mental well-being. Legal: substance recognized in the official pharmacopoeia or formulary of the nation. |
| What is the definition of a drug according to the Federal Food, Drug, and Cosmetic act? | articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals" and "articles (other than food) intended to affect the structure or any function of the body of man or other animals” |
| What are generic drugs? | Drugs that have the same dosage, indications, contraindications, side effects, route of administration and safety (same pharmacological effects) as the original brand-name drug. |
| What is the difference between generic drugs and brand name drugs? | For generics, inactive ingredients, size, shape, flavors and color of generic drug may not be the same as that of brand-name counterpart. |
| When can a pharmacist substitute generic drugs in for brand name drugs? | Each state has a law allowing pharmacists to substitute generic drugs (therapeutic equivalent) for many brand-name products as long as the prescriber doesn’t specify that the brand-name drug is required. |
| What is off-label use of a drug? | usage of the prescription drug for an indication, in an age group, in a dose, or by route of administration that was not approved by the Food and Drug Administration (FDA) |
| In the US, is it legal for physicians to practice off-label usage of drugs? | Yes; FDA cannot interfere with practice of medicine, but physicians should be well informed about drug and make decisions about off-label use based on firm scientific rationale and rigorous medical evidence |
| Can drug companies promote off-label use for drugs? | It is illegal for companies to promote off-label uses of their prescription drugs, but they can provide physicians with off-label information in response to an unsolicited request. |
| What are over-the counter (OTC) drugs? What safety concerns should you have? | OTC drugs are defined as drugs that are safe and effective for use by the general public without seeking treatment by a health professional (definition by FDA) and therefore do not require prescription. Check for drug/drug interactions |
| What is an investigational new drug? | Drug that has not been approved for general use but is under investigation in clinical trials regarding its safety and efficacy. |
| What things are required for a physician to prescribe an investigational new drug? | Requires FDA approval of an IND application, (includes reports of animal toxicity tests, descriptions of proposed clinical trials, and a list of the investigators that will be involved in the clinical trials. |
| What is an orphan drug? | An orphan drug is a pharmacological agent that has been developed specifically to treat a rare medical condition (orphan disease). |
| What is a first-line drug? | Recommended for the initial treatment of a disease, sign or symptom, usually on the basis of empirical evidence for their equal/similar efficacy. |
| Why is choosing a first-line drug difficult? | There are few studies of head-to-head comparisons of drugs with similar therapeutic effects; usually there is no incentive for pharmaceutical companies to sponsor these type of studies. |
| What is a drug of choice? | This is a drug or group of drugs that has additional therapeutic effect (niche) over similar drug or group of drugs. |
| What is a "me too drug"? | Drug that is very similar to already approved drug(s), with only minor structural differences. |
| How are dosages recommended? | Determined in FDA-mandated clinical trials are for "average adult" patient; based on a positive therapeutic response with no/minimal or tolerable side effects in the majority (of highly homogenous group) of patients, |
| What is drug affinity? | Tendency of a molecule to associate with another. The affinity of a drug is its ability to bind to its biological target. |
| What is the intrinsic activity of a drug? How does this affect potency? | Drugs vary in their ability to produce an effect. Binding affinity alone does not determine the overall potency of a drug. |
| What is the potency of a drug? | measure of drug activity expressed in terms of the amount required to produce an effect of given intensity; it is a function of the affinity and intrinsic activity. NOT THE SAME AS EFFICACY; potency is less important clinically |
| What is the efficacy of a drug? | Capacity of a drug to produce a desired effect; measured as the potential maximum therapeutic response that a drug can produce. |
| What is the difference between efficacy and effectiveness? | Clinical studies of drug efficacy determine whether tested drugs produce the expected responses under ideal circumstances. Effectiveness trials (outcome trials) measure the degree of beneficial effects of drugs under “real world” clinical settings. |
| What is selectivity? | Degree to which a set dose produces the desired effect in relation to adverse effects. |
| Are more selective drugs necessarily safer? | In general, interact with very specific targets-->better side-effects profile. Exceptions to this rule (COX-2 inhibitors); high selectivity DOES NOT guarantee safety. In clinical, selectivity may be relative, i.e. may disappear with increasing dose. |
| How is the safety of drugs determined? | Randomized clinical trials in a limited number of patients. The final safety profile of a new drug is established in years to come after drug approval. |
| What is an adverse drug reaction (ADR)? | Response to a drug which is noxious, unintended, and occurs at doses normally used, i.e. ADR is a harm directly caused by the drug at normal doses, during normal use. |
| What is a type A reaction? | Predicable, common and related to the pharmacologic actions of the drug that may occur in any patient. |
| What is a type B reaction? | Unpredictable, uncommon and usually not related to the pharmacological actions of the drug that occurs only in susceptible individuals. |
| What is an adverse drug even? How is it different from an adverse drug reaction? | An adverse drug event is an injury resulting from the use of a drug. It is a broader term than ADR and includes ADR and harm from the use of the drug (including dose reductions and discontinuations of drug therapy and medical errors). |
| What is a therapeutic index (or therapeutic ratio)? | comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes death (in animal studies) or toxicity (in human studies). |
| How do you calculate the therapeutic index/ratio? | ratio given by the toxic dose divided by the therapeutic dose, i.e. the toxic dose of a drug for 50% of the population (TD 50 ) divided by the minimum effective dose for 50% of the population (ED 50 ). |
| What is a therapeutic window? What's important to rememeber when prescribing these? | Range of drug dosages that can treat the disease effectively while staying within the safety range (between desired effect and toxic range). May require drug blood levels monitoring to both achieve therapeutic levels and to minimize toxicity. |
| What is the standard safety factor (standard safety measure)? How does it compare to the therapeutic index? | ratio of the toxic dose for 1% of population to the effective dose for 99% of the population (TD1/ED99). This is a better safety index than the therapeutic index if the quantal dose-response curves for the desired and toxic effects are not parallel |
| What are the two most common mechanisms of drug action? | Antagonize/block/inhibit endogenous proteins; activate endogenous proteins |
| What are some unconventional mechanisms of action for drugs? | disrupt structural proteins, react chemically with small molecules, bind free molecules, act as enzymes or nutrients, drug action is due to their physical properties, or drugs have antisense action. |
| What are the four phases of drug evaluation and approval? | Phase 1, 2, 3, and 4 |
| What is phase 1 of a drug trial? What information is of primary interest? How many participants? What else is collected? | The effects of the new drug as a function of dosage are examined in 20-100 healthy volunteers or volunteer patients. Primary focus is on the safety of the clinical dosage range (dose-escalating studies). Initial pharmacokinetic data is also collected. |
| What is phase 2 of a drug trial? What information is of primary interest? How many participants? What else is collected? | The drug is studied in a modest number of patients (100-200) with targeted disease. Determine the efficacy (so called proof of concept studies) and define dose that will be used in future clinical trials. These studies have the highest rate of failure |
| What is phase 3 of a drug trial? What information is of primary interest? How many participants? What else is collected? | Larger # patients (>1000) with target disease. Goal: further establish + confirm safety and efficacy. FDA approval based (only) on its efficacy and safety established in at least two phase 3 trials or in multicenter trial. |
| What is phase 4 of a drug trial? What information is of primary interest? How many participants? What else is collected? | A post-marketing (surveillance) evaluation is crucial in determining the actual safety of a new drug. By prescribing and taking the new drug, the physician and his/her patient are becoming participants in the “final drug evaluation study”. |
| What are some factors that can affect how patients differ in terms of drug response? | Patients may significantly differ in regard to body size and body composition (children vs. adults vs. elderly; obese patients; patient with ascites), drug distribution, drug tissue binding, and the body’s capacity to metabolize and eliminate the d |
| Which type of drug (in terms of metabolism) are more variable in their response? | The ravariability in the pharmacological response is more common with drugs disposed by metabolism than with drugs excreted unnchanged in urine. |
| What is patient compliance? How does it affect medical care? What parameters are used to measure compliance? | The degree to which a patient correctly follows medical advice not only in terms of taking medications medication or drug compliance but also in following diets, executing life-style changes, keeping appointments and self-monitoring of treatment. |
| When is a patient considered compliant? | If 80-90% of medications are taken |
| What aspect of drug design do intestinal motility/integrity, small intestine transit, splanchnic blood flow, and metabolism of drug before reaching systemic circulation influence? | These will change the absorption of a drug |
| Most drugs in the plasma are reversibly bound to ____, mainly to _____ and ________. | proteins; albumin, alpha-1-acid glycoprotein |
| Acidic drugs normally bind to _____ (protein), whereas basic drugs more commonly bind to ____ | albumin, alpha-1-acid glycoprotein |
| How does protein binding affect the concentration of drug available in tissues and at the site of action? | It limits it (since protein binding acts as a sink); tissue binding may serve as reservoir, though it may cause damage to tissue/organ |
| What are the four different pharmacokinetic factors that can cause drug-drug interactions? | Absorption, distribution, metabolism, and elimination |
| When is a drug interaction additive? | When the combined effect of trwo drugs is equal to the sum of the effect of each drug. |
| What is a synergistic effect? | When the combined effect exceeds the sum of the effects of each drug alone |
| What is potentiation? | One drug has no effect when given alone but increases the effect of a second active drug |
| What is pharmacological antagonism? | Interference of one drug with the action of another at receptor level |
| What is physiological antagonism? | When two drugs produce opposite effects on same physiological function via two different sites (receptors) |
| What is chemical antagonism (aka antagonism by neutralization)? | 2 drugs react chemically to form an inactive product without the involvement of drug receptors |
| Why do observed drug responses differ from expected drug responses? | Most of data about drug response comes from randomized clinical trials of drug efficacy in homogenous group of patients + restricted conditions and under careful and intense monitoring-->do not “mimic” conditions under which drug will be used normally |
| What is the external validity of a study? | How applicable the literature data is to the real practice of medicine. |
Created by:
karkis77
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