What are the factors that increase the incidence of drug interactions?
- Drug-Drug Interactions
- Drug-Food Interactions
- Drug-Laboratory Test Interactions
- Drug-Environmental Interactions
What individual patient variables increase the incidence of drug interactions?
- Age: Very old, Very young
- Genetic Factors
- Disease States: Renal disease, Liver disease
- Renal Function
- Liver Function
- Environmental Factors
- Individual Variation
What are the two major mechanisms for drug interactions?
- Alteration of pH: bisacodyl (Dulcolax�) - antacids, ketoconazole (Nizoral�) - H2 antagonists
- Complexation and Adsorption: tetracycline (Sumycin�) - metals (calcium, aluminum, iron); colestipol and cholestyramine - many drugs (digoxin); adsorptive type anti-diarrheal medications (Kao-Pectate)
- Alteration of Motility: Cathartics (laxatives): Magnesium citrate, Castor oil; Anticho1inergics(Dentrol LA); Food
- Alteration of Distribution: Displacement from protein binding sites aspirin - warfarin (Coumadin), phenytoin (Dilantin) - warfarin (Coumadin); Hypoalbuminemia
- Stimulation of Metabolism (Enzyme Inducers): carbamazepine (Tegretol), phenytoin (Dilantin), phenobarbital, alcohol, smoking
- Inhibition of Metabolism: Enzyme Inhibition, cimetidine (Tagamet), erythromycin (E-Mycin), verapamil (Calan, Isoptin), grapefruit juice
- Alteration of Excretion: A1teration of Urine pH, Interference with Urinary Excretion
- alkaline urine
- decreased excretion of bases
- increased excretion of acids
- increased excretion of bases
- decreased excretion of acids
Drugs Having Opposite Effects, beta blockers - beta agonists, anti-hypertensives - decongestants
Drugs Having Similar Effects: alcohol - sedatives and other CNS depressants, theophylline (Theo-Dur) - beta agonists
- Alteration of Electrolyte Levels, diuretics - digoxin (Lanoxin)
- Alteration of Receptor Sites: anabolic steroids - warfarin (Coumadin), anabolic steroids - glyburide/glipizide (Micronase, Diabeta, Glucotrol)
- Alteration of GI flora: antibiotics - oral contraceptives
- Antibiotic Combinations: penicillin � tetracycline
Reference Sources on Drug Interactions
- Specific Texts: Drug Interaction Updates (Hansten & Horn), Evaluations of Drug Interactions (Shinn & Shrewsbury), Drug Interaction Facts (Tatro)
- General References: AHFS, Facts & Comparisons, USP DI
Prevention of Disease
Elimination of Disease
Examples: Antibiotics, H2 Antagonists
Treatment of Symptoms
Examples: Anti-inflammatory Drugs, Cold Remedies
Arrest Progression of Disease
Diagnosis of Disease
Examples: Tensilon�, Persantine IV�
FDA Pregnancy Categories
- A, no risk
- B, Risk cannot be ruled out
- C, Caution is advised
- D, Is a definite risk
- X, Do not use
Drugs not deemed safe for use without direct medical supervision. Stock bottles of these drugs must contain the symbol �Rx Only� or the following statement printed on the label: �Caution: Federal Law prohibits dispensing without a prescription.�
- a "United States Adopted Name" (USAN) is selected by the USAN Council
- shortened version of the chemical name.
The study and identification of natural sources of drugs
A Greek word meaning a magic spell, remedy, or poison that used in early records to represent the concept of a drug.
- Entrance of the drug into the blood stream.
- Factors That Affect Absorption
- Solubility of Drug
- Site of Administration, Oral, Parenteral, Topical
- Drug Ionization, un-ionized drug enhanced drug absorption.
- Drugs already in solution will be absorbed faster
- The smaller the particle size of the drug, the faster the rate of dissolution and absorption
The process by which a drug; is carried to the various tissues and organs of the body.
The enzymes responsible for drug metabolism
The process by which materials, including drugs, are removed from the body to the external environment.
Sites of Excretion
Kidney, Feces, Lung, Sweat, Tears, Saliva., Breast Milk
What is first pass metabolism? What routes of administration can be used to avoid this effect?
After oral administration, all drugs are carried by the bloodstream to the liver before they are distributed to other tissues or organs. Some drugs are metabolized significantly on this first pass through the liver. This is known as the first-pass metabolism. It can greatly reduce the amount of active drug that reaches the site of action.
What is half life?
the time it takes 1/2 of the drug in the body to be eliminated.
List several reasons for coating tablets.
- Taste, bad taste and foul odors
- Stability: oxygen, light, or moisture in the atmosphere
- Prevent Contact with Drug: Aspirin - Ecotrin
- Separate Active Ingredients: Two ingredients
- Control Rate of Release: alter the rate of release of a drug
- Control the Site of Release: specific sites
- Improve Appearance: have a visually pleasing product
- Prevent Loss of Volatile Ingredients
What are the reasons for enteric coating?
- Enhance drug stability and to control the rate of drug release.
- Prevent gastric degradation or digestion
- Prevent gastric mucosal irritation (Ecotrin, Ery-Tab)
- Prevent dilution of drug prior to reaching its site of action (Azulfidine)
- Provide delayed action
- Control or monitor physiological location of drug delivery
What is compliance? How do coatings and extended action preparations relate to compliance?
A patient�s adherence to the dose schedule and other particular requirements of the specified regimen.