Chapter One - TextBook (Lippincott.) Flashcards
Pharmacokinetics
Refers to what the body does to a drug, whereas pharmacodynamics describes what the drug does to the body
There are four pharmacokinetic properties that determine the onset, intensity, and the duration of drug action
Absorption
Distribution
Metabolism
Elimination
Absorption
First, absorption from the site of administration permits entry of the drug (either directly or indirectly) into plasma
Distribution
Second, the drug may then reversibly leave the bloodstream and distribute into the interstitial and intracellular fluids.
Metabolism
Third, the drug may be bio-transformed by metabolism by the liver or other tissues
Elimination
Finally, the drug and its metabolites are eliminated from the body in urine, bile, or feces
Routes of Drug Administration
Many include enteral, parenteral, and topical, among others
Enteral Administration
The safest and most common, convenient, and economical method of drug administration.
Different methods of Enteral Administration
The drug may be swallowed, allowing oral delivery, or it may be placed under the tongue (sublingual), or between the gums and check (buccal), facilitating direct absorption into the blood stream.
Oral administration provides many advantages
Self Administered, and toxicities and/or overdose of oral drugs may be overcome with antidotes. Example: Activated Charcoal
Enteric Coated Preparations
Chemical envelope that protects the drug from stomach acid, delivering it instead to the less acidic intestine, where the coating dissolves and releases the drug
Enteric coating is useful for certain drugs that are
- acid unstable such as omeprazole
- irritating to the stomach, such as aspirin
Extended release preparations
- Special coatings or ingredients that control the drug release, thereby allowing for slower absorption and a prolonged duration of action
- Can be dosed less frequently and may improve patient compliance
Extended release preparations may maintain concentrations within
The therapeutic range over a longer period of time, as opposed to immediate-relate dosage forms, which may result in larger peaks and troughs in plasma concentration
ER formulations are advantageous for drugs with
Short half-lives…For example oral morphine is 2-4 hours, and it must be administered six times daily to provide continuous pain relief. However, only two doses are needed when extended-release tables are used.
Sublingual/Buccal allows a drug to?
Diffuse into the capillary network and enter the systemic circulation directly
Buccal is similar to the
sublingual route
Sublingual administration has several advantages
- Ease of administration
- Rapid absorption
- Bypass of the harsh GI environment
- Avoidance of first pass metabolism
Parenteral
This route introduces drugs directly into the system circulation
Parenteral administration is used for drugs that are?
- Patient is unconscious and in circumstances that require a rapid onset of action
- Poorly absorbed form the GI tract (ex. Heparin) or Unstable in the GI tract (ex. Insulin)
Which route has the highest bioavailability and are not subject to first-pass metabolism or the harsh GI environment?
Parenteral Administration which provides the most control over the actual dose of drug delivered to the body
Which Administration is irreversible?
Parenteral which may cause pain, fear, and local tissue damage, and infections
What are the three major parenteral routes?
Intravascular (Intravenous or intra-arterial)
Intramuscular
Subcutaneous
Most common parenteral route
Intravenous
When would a Intravenous administration be useful?
For drugs that are not absorbed orally such as the neuromuscular blocker rocuronium.
When IV is injected as a bolus what is the amount delivered?
The full amount of drug is delivered to the systemic circulation almost immediately
When IV is administrated as an infusion?
The drug is infused over a longer period of time, resulting in lower peak plasma concentrations and an increased duration of circulating drug levels.
IV administration is advantageous for drugs that cause?
Irritation when administered via other routes, because the substance is rapidly diluted by the blood.
Adverse Reactions of IV administration?
- Higher risk of infection to the site
- Induce hemolysis
- If delivered too quickly, higher concentrations
Intramuscular Route
Drugs administered this route can be administered in aqueous solutions, which are absorbed rapidly, or in specialized depot preparations which are absorbed slowly.
Depot preparations often onsite of?
Suspension of the drug in a non aqueous vehicle such as polyethylene glycol
What is the MOA for Depot Preparations?
- As the vehicle diffuses out of the muscle, the drug precipitates at the site of injection
- The drug then dissolves slowly, providing a sustained-release drugs are haloperidol and depot medroxoyprogesterone
Subcutaneous (SC) is similar to which kind of injection?
IM injection, This route provides absorption via simple diffusion and is slower than IV route.
SC injection minimizes the risks of?
Hemolysis or thrombosis associated with IV injection and may provide constant, slow, and sustained effects.
SC should not be used with which drugs?
Drugs that cause tissue irritation , because severe pain and necrosis may occur.
Drugs commonly administered via SC route include?
Insulin and Heparin
Oral Inhalation both oral and nasal provide what kind of delivery?
Rapid delivery of a drug across the large surface area of the mucous membranes of the respiratory tract and pulmonary epithelium
Oral inhalation drug effects are almost as rapid as those with?
IV bolus
Drugs that are gases and those that can be dispersed in an aerosol administered?
Inhalation
Oral Inhalation is effective and convenient for patients with?
Patients with repository disorders such as asthma or chronic obstructive pulmonary disease, because the drug is delivered directly to the site of action, thereby minimizing systemic side effects.
Examples of drugs administered via inhalation include?
Bronchodilators such as albuterol, corticosteroids such as fluticasone.
Nasal Inhalation
Directly into the nose.
Examples of nasal agents include?
Nasal decongestants, such as oxymetazolin, and corticosteroids such as mometasone furoate.
Desmopressin (for diabetes insipidus)
Intrathecal/intraventricular is mainly used because?
The BBB typically delays or prevents the absorption of drugs into the CNS
Intrathecal are used for local, rapid effects, it is necessary to introduce drugs directly into the?
CSF
Topical Application is used when?
A local effect of the drug is desired.