Module 2 Chapter 4 and 5 Flashcards
Why isn’t the dose the same for each route of administration?
because the body “handles” the drug differently depending on the route of administration
Pharmacodynamic effects
“what the drug does to the body”. Ex. does the drug make you sleepy, does it make your lungs dilate, does it treat an infection?
Pharmacokinetics
“what the body does to the drug”
the measured response to time and dose (absorption, blood levels, mode of inactivation, etc. )
Kinetic terms
The drug Cycle
I .Absorption II . Distribution (plasma) III . Metabolism IV . Excretion The Drug Cycle deals with the pharmacokinetic variables (absorption, Distribution, Metabolism and Excretion)
The steps of the Drug Cycle describe how much of administered dose of drug (say, given orally) is absorbed, which body fluids it is distributed to, how long it stays in the blood before being metabolized and when, and where it is excreted.
Absorption
***fraction of drug in circulation
involves the movement of a drug from the site of administration through tissues and into the blood. involves three steps:
1. Disintegrate - tablets, capsules, suppositories
2. Dissolve - dissolve by saliva, gastric juice or tissue fluid
3. Absorb - drug passes through the walls of nearby capillaries and is absorbed into the blood
distribution
***how the drug partitions in the body
where the drug goes in the body
T 1/2 (half life)
the time required for the serum drug level to decrease by 50%
Metabolism
the way the drug is broken down
Excretion
the way it is cleared from the body
Pharmacokinetic factors
Bioavailability blood level half life first pass effect therapeutic index
Albumin
is only one of many proteins that exist in the blood. binder of drugs floating in the plasma. some drug bind to albumin more than others
BBB
BLOOD BRAIN BARRIER
exists between the cerebral capillaries and the neurons of the CNS. Some drugs cannot pass through the BBB therefore it can’t treat the disease.
***Ritalis and anesthetic drug can pass through the BBB
Metabolism or Biotransformation
drug is transformed from it’s initial, usually active form to a different form (usually, but note always more inactive)
the liver
IS the main organ for the metabolism of drugs
drugs that are absorbed in the gut pass through the liver first before they go anywhere else “enterohepatic circulation”
***Liver has importance function to drug metabolism.
First Pass Effect
in the liver they are acted on by a series of “microsomal” liver enzymes in a “First Pass Effect”
***initial metabolism by the liver
Oral lidocaine
given in huge doses (compared to how much is needed if injected into the site to be numbed) to compensate for the first pass effect.
morphine-like opioids, nitroglycerine
metabolized the first time through the liver before they get into the systemic circulation
Kidneys
most drugs are excreted from the body by the kidney
Name two other ways that drugs are excreted
Bile - from the liver back to the GI tract
The lungs
Mothers’ milk
Saliva, Sweat and Tears
the therapeutic effect
***desire clinical effect
is intended to prevent a disease, to diagnose a disease or to treat a disease by controlling, improving or curing the symptoms of the disease
topical administration
Absorption
does not need to undergo disintegration, it quickly dissolved in the tissue fluids of the skin.
DO NOT complete the final step of absorption and do not go into into the blood.
Their therapeutic effect is only exerted locally at the site of administration.
transdermal administration
patches
the drug in the patch reservoir begins to be released
because the drug is in the liquid form.
DO NOT need to undergo disintegration. it quickly dissolved in the tissue fluids of the skin passes through the walls of near by capillaries and it absorbed into the blood.
Oral administration
drug form disintegrates, if necessary. it then dissolved in stomach or intestinal fluids then go through the last step of the absorption.
inhalation administration
the vaporized lipid or gas - does not need to undergo disintegration
Vaginal or rectal administration
drug form disintegrates and releases the drug topically into the vagina.
Always intended to have only a topical therapeutic effect and there is minimal absorption into the blood.
*** the rate of absorption following rectal administration is rather slow and variable.
parenteral administration
following intradermal, subcutaneous, and intramuscular injections, the drug is already in a liquid form and so it quickly dissolved in the tissues fluids of the skin, passes through the walls of nearby capillaries and is absorbed into the blood.
*** IV injections entirely bypass the steps of absorption because the drug is administer directly into a vein and immediately enters the blood.
Lidocaine (Xylocaine) -use to treat? administration route?
***given IV/tropical/or transdermal to treat cardiac arrhythmia. Also use for nerve block.
cannot be given orally because no active drug remains after the first pass effect.
nitroglycerin
administered orally
Elderly persons
Premature babies
declines in liver and kidney functions
***drug doses need to be reduced (prescribed lower doses) to compensate for the prolonged action of un-metabolized drug in the blood and to prevent toxicity from high levels of drug.
Excretion
Kidney, saliva, tears, sweat and breast milk
the body get rid off waste products (inactive drug metabolites) and removing active drugs that are not metabolized by the liver.
All of these administration routes…except the I.V. parenteral route, I.M parenteral route
must be “absorbed” and pass through some type of membrane or tissue into the blood and then into the target cells.
The amount absorbed determines the “bioavailability of the drug
the administered dose of unchanged drug that reaches the systemic circulation
sometimes we don’t want the drug absorbed systemically (throughout the body)
Bowel sterilization pre-surgery (neomycin-an antibiotic that is not absorbed-only effects the gut)
Vaginal administration (Premarin-hormone replacement for vaginal tissue, or anti yeast creams)
Rectal route (analgesics for hemorrhoids)
Carafate (anti ulcer drug-binds exposed proteins of ulcer
morphine -oral dose vs parenteral dose
must be given in higher doses orally than parenterally because of the first pass metabolism.
Chloral-hydrate
does not induce sleep until it is metabolized int he liver to a more active form
