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What is the USP?
United States Pharmacopaceia. They set the standards for purity/quality for any substance that goes into medications.
What are three routes for parenteral administration?
IV, IM, SQ
Where does most drug metabolism occur?
In the LIVER
What is another term for "Biotransformation"?
What is a metabolite? What's the difference between an "active" and "inactive" metabolites?
- Metabolity = The intermediate products of metabolism.
- An active metabolite is an active form of the drug. An inactive metabolite is a breakdown product that doesn't produce a therapeutic effect.
What are Cytochrome P450 Enzymes?
A set of enzymes in liver whose function is to break things down - "hepatic drug metabolizing enzymes". Cytochrome P450 system, AKA "hepatic microsomal enzyme system". About 60 members of this class. We'll be sick of them by the end.
What can happen when 2 different drugs are metabolized by the same CYP450 enzymes?
They can become more or less active due to various factors.
What effect does alcohol have on CYP450 enzymes?
Alcohol speeds up these enzymes, which can speed up metabolism & inactivate drug.
Name 3 substances that can impact CYP450 enzymes.
- Grapefruit juice
What is the main route of excretion for most drugs?
What are 5 nonrenal routes of drug excretion?
- breast milk
- respiration via lungs
What is the "first-pass effect"?
- When a drug is swallowed, it is absorbed by the digestive system and goes straight into the hepatic portal system. From there, it first goes to the liver before it reaches the rest of the body. This can greatly reduce the bioavailability of the drug.
- Some drugs are converted from an inactive to active form during the first pass (ex: Codeine)
What type of molecules can easily pass through cell walls (lipid bilayers)?
- Pure lipid bilayers are generally permeable only to small, uncharged solutes.
- Note: Ions are CHARGED and do not easily pass through cell membranes.
What type of drug will be more readily absorbed in the stomach: acid or base?
- Acidic. Non-ionized drugs can pass through more easily.
- In the stomach, drugs that are weak acids (such as aspirin) will be present mainly in their non-ionic (non-charged) form, and weak bases will be in their ionic form.
What type of drug will be more readily absorbed in the intestine: acid or base?
- Acids ionize in an alkaline environment, and bases ionize in an acidic environment.
- EXAMPLE: asprin will not be absorbed from the small intestine, which is a more basic environment.
- NOTE: The majority of drugs are more alkaline, so they will be ionized (charged) in the acid environment of the stomach, then become deionized in the small intestine, where they can then be absorbed.
Why do infants need smaller doses of many drugs?
- They have reduced renal function, and cannot renally excrete drugs as efficiently as adults.
- They also have immature liver function and cannot metabolize alcohol.
- In addition, their blood-brain barriers and protein-binding systems are not fully developed.
- And be careful with topicals due to their thin skin.
Why are ionized drugs easily secreted in the urine?
Elimination of drugs from the body takes place in much the opposite way as for drug absorption. The liver metabolizes most drugs to a water-soluble, ionized form for excretion. Non-ionized drugs will generally return to circulation.
What factor can increase excretion of a drug in breast milk?
Low molecular weight
A drug that inhibits CYP450 enzymes can have what effect on another drug that is metabolized by CYP450?
- It can decrease metabolism of the other drug by CY450 enzymes, leading to increased (possibly toxic) levels of the drug in the bloodstream.
- Or, decreased metabolism might cause a decrease in teh intended effect of the drug. ****Need to research this more.
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