unit 1

what is a protoype drug?

well understood drug model with which other drugs in its representative class are compared

what is a chemical name?

• International Union of Pure and Applied Chemistry (IUPAC)

• helpful in predicting a substance’s physical and chemical properties

what is a drug’s mechanism of action?

how a drug produces its physiologic effect in the body or how a drug works in the body to produce its effect

what are the U.S. drug regulations that have provided guidelines for the safe and effective use of drugs and drug therapy?

• Food, Drug, and Cosmetic Act: requires drugs to be tested for safety

• Pure Food and Drug Act: ensures accurate labeling

• “USP Label”

• FDA: regulates and monitors drugs

  • CDER

  • CBER

what is the Center for Drug Evaluation and Research?

• branch of the FDA

• exercises control over whether prescription and over the counter drugs may be used for therapy

• facilitates the availability of safe, effective drugs » keeping unsafe or ineffective drugs off the market

• provides clear, easily understandable drug information for safe and effective use

what is the Center for Biologics Evaluation and Research?

regulates the use of biologics, including serums, vaccines, blood products

What is the FDA’s role in the drug approval process?

1. preclinical investigation

2. clinical investigation

3. review of the new drug application (NDA)

4. postmarketing surveillance

what is preclinical investigation phase and its purpose?

• tests on human cells and animals

• examine drug’s effectiveness at different doses and look for adverse effects

• Investigational New Drug application if there are significant therapeutic benefits and product is reasonably safe for initial use in humans

what is clinical investigation phase and its purpose?

• perform tests on volunteers » determine proper dosage and assess for adverse effects

• determines if drug is

  • effective

  • worsens other medical conditions

  • interacts unsafely with existing medications

  • affects one type of patient more than others

• if drug appears effective and no serious side effects » approval marketing accelerated or may be used in special cases with careful monitoring

what is the review of the New Drug Application phase and its purpose?

• drug’s trade name finalized

• FDA reviews NDA

what is an Investigational New Drug application?

application submitted for clinical trials when it is determined that there are a significant therapeutic benefits and product is reasonably safe for initial use in humans

what is postmarketing surveillance phase and its purpose?

• survey for harmful drug effects in larger population

• FDA discovers serious problem » drug withdrawn from market

what is the prototype approach to drug classification

studying one representative drug (prototype) to understand the entire drug class, including mechanism, effects, and side effects

what’s the difference between prescription and over the counter drugs?

prescription

• requires written order from HCP

• HCP can maximize therapy by ordering proper drug for patient’s condition and conveying amount and frequency of drug to be dispensed

• patient education

over the counter

• does not require HCP order = easier to obtain

• pt may treat themselves safely if they carefully follow instructions with medication; if not = serious adverse effects

• no appt with HCP required = saves time and money

• may react with foods, herbal products, prescription medications, other drugs

why are some drugs placed on a restrictive/warning list?

high potential for addiction » dependence » withdrawal

what are scheduled drugs?

• drugs classified according to their potential for abuse

• schedule I

  • highest potential

  • restricted for use in situations for medical necessity

  • little or no therapeutic value and only intended for research purposes

• schedule V

  • lowest potential

  • drugs may be dispensed without prescription because quantities are so low that possibility of dependence is remote

what is the Controlled Substances Act or Comprehensive Drug Abuse Prevention and Control Act?

hospitals and pharmacies must

• register with Drug Enforcement Administration and use assigned registration numbers to purchase scheduled drugs

• maintain complete records of all quantities purchased and sold

• telephone orders to pharmacy not allowed

• refills for schedule II drugs not allowed

• severe penalties for unlawful distributing

what is a teratogenic risk?

drugs categorized into A, B, C, D, X

• category A: safest group of drugs

• category X: most dangerous to fetus

what is a teratogen?

substance that has the potential to cause a defect in an unborn child during mother’s pregnancy

why should nurses be mindful of teratogenic risks?

birth defects are most probable in first trimester

what should you be mindful about when it comes to enteral route?

• given orally, NGT, gastrostomy tube

• safest route » skin barrier is not compromised

• overdose » induce vomiting

what should you be mindful about when it comes to enteric coated tablets?

• hard, waxy barrier to resist acidity

• dissolve in alkaline environment of small intestine

• DO NOT CRUSH » medications would be directly exposed to stomach environment

what should you be mindful about when it comes to sustained release tablets/capsules?

• dissolve very slowly » releases over extended time » longer duration of action

• allow for convenience of once or twice a day dosing

• DO NOT CRUSH/OPEN

what should you be mindful about when it comes to sublingual route?

• under tongue » dissolve slowly

• rich blood supply in region » rapid onset of action

• should be administered after oral meds

• pt should not move med with tongue, eat, drink

what should you be mindful about when it comes to buccal route?

• oral cavity between gum and cheek » slower absorption

• pt should not move med with tongue » displaced to sublingual area and be more rapidly absorbed or to back of throat and swallowed

what should you be mindful about when it comes to topical drugs?

• applied locally to skin, membranous linings of eye, ear, nose, respiratory tract, urinary tract, vagina, rectum » local effect

• absorbed very slowly

what is pharmacokinetics?

the study of drug movement throughout the body

what are the four components of pharmacokinetics?

• absorption

  • process involving movement of substance

• distribution

  • transport of drugs throughout body

• metabolism

  • chemically converting a drug to form that is more easily removed from body

• excretion

  • process that removes drugs from the body

what factors affect drug absorption?

• rate of dissolution: faster drug disintegrates and disperses » faster absorption

• drug formulation: liquids > tablets/capsules

• dose: higher dose » faster onset

• route: IV » bloodstream » absorption to tissues faster

• size: small > large

• surface area of absorptive site: larger surface area » faster absorption

• digestive motility: changes in GI motility can speed up or slow down absorption

• blood flow: greater blood flow to site of drug administration » faster absorption

• lipid solubility of drug: lipid soluble drugs > water soluble drugs

• degree of drug’s ionization: nonionized form (weak base + alkaline environment / weak acid + acidic environment) > ionized form

how do drug–drug and food–drug interactions affect drug absorption?

• administering tetracyclines with food or drugs containing calcium, iron, magnesium » delay absorption

• high fat meals » slow stomach motility

• dietary supplements

• ingredients in herbal weight loss products » laxative effect » decrease intestinal transit time » reduce drug absorption

what factors affect drug distribution?

• blood flow: more blood flow » greater distribution (heart, liver, kidneys, brain > skin, bone, fat)

• lipid solubility: lipid-soluble agents » water-soluble drugs

• affinity: some tissues (bone, fat, teeth) store drugs » prolonged effects

• protein binding: drugs bind reversibly to plasma proteins (albumin) » drug protein complexes » too large to cross » circulate

  • only unbound (free) drugs can reach target cells

• barriers: blood brain barrier and placental barrier prevent chemicals and meds from entering

  • fetal-placental barrier prevents potentially harmful substances from passing from mother’s bloodstream to fetus, however, not alcohol, cocaine, caffeine, certain meds

what factors affect drug metabolism?

• liver function: primary site of metabolism » liver damage (cirrhosis) » decreased metabolism

• CYP enzyme: breaks down drugs

• enzyme induction: drugs increase metabolism » decrease drug levels

• enzyme inhibition: drugs decrease metabolism » increase drug levels

• age: infants, older adults

• genetics

• first-pass effect

what is the first-pass effect?

1. oral drug

2. drug absorbed across intestinal mucosa

3. drug enters portal circulation and travels to liver

4. first pass through liver, drug is metabolized to less active form

5. drug metabolites (less active) leave the liver for distribution to tissues

what factors affect drug excretion?

• kidney function: primary organ of excretion » impairment » lowers excretion

• blood flow: increased renal blood flow » increased excretion

• drug ionization: ionized drugs excreted > non-ionized drugs reabsorbed

  • urine pH: weak acids + alkaline urine / weak base + acidic urine » excreted faster

• lipid solubility: water soluble drugs excreted > lipid-soluble drugs reabsorbed

• protein binding: protein-bound drugs are not filtered » lowers excretion

• age: infants, older adults

• other routes: lungs, bile, sweat, saliva, breast milk can also eliminate drugs

what is a drug’s onset?

represents the amount of time it takes to produce a therapeutic effect after drug administration

what is a drug’s peak?

occurs when medication has reached its highest concentration in the bloodstream

what is a drug’s duration?

amount of time a drug maintains its therpeutic effect

what is a drug’s plasma half life?

• length of time required for a medication’s plasma concentration to decrease by one half after administration

• longer it takes a medication to be excreted, greater the half life

• extensive kidney or liver disease » drug’s plasma half life increases » drug concentration may reach toxic levels

• ex: aspirin; 15-20 min half life, given every 3-4 hours

• ex: felodipine; 10 hr half life, given once a day

what’s the difference between loading and maintenance doses?

loading dose

• large initial dose

• given once or a few times

• rapidly reaches therapeutic drug level

• used when quick effect is needed or drug has a long half-life (ex: antibiotic for severe infection)

maintenance dose

• smaller, regular doses

• given at set intervals

• keeps drug levels within therapeutic range

• prevents levels from dropping below effective range » allows plateau drug plasma level to be reached