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CYP450 Inhibitors
- Many meds are metabolized in the liver enzyme system called
CYP450. Metabolization can be inhibited or induced by drugs and once this happens drug-drug interactions can occur.
Inhibitors (VISA credit card debt inhibits spending on designers like CK to look GQ)
- Valproate, Isoniazid, Sulfonamides, Amiodarone, Chloramphenicol,
Ketoconazole, Grapefruit Juice, Quinidine
What do inhibitors do?
- Decrease medication metabolism. INHIBIT the metabolic activity of
one or more of the CYP450 enzymes. This potentially slows the activity or blocks the activity required for metabolism of other medications, thereby increasing the levels of medications dependent on that particular enzyme for biotransformation. This inhibition prolongs the pharmacological effect, which may result in toxicity.
Factors that affect inhibition are:
- Dose and the capacity to bind the enzyme.
What can happen if not used correctly? What would the patient experience?
- If a medication is taken with an inhibitor, the level of the drug can
increase and result in adverse effects 1 / 3
CYP450 Inducers (BS, CRAP, GPS Induces Rage)
- Barbiturates, St. John’s Wort, Carbamazepine, Rifampin, Alcohol,
Phenytoin, Griseofulvin, Phenobarbital, Sulfonylureas
What do inducers do?
- Increase medication metabolism. Inducers are xenobiotics
(medications and environmental agents) that elevate CYP450 enzyme activity by increasing enzyme synthesis.
What do they cause if not used correctly? What would the patient experience?
- An inducing agent can increase the rate of another drug's
metabolism. Therefore, when an inducing agent is prescribed with another medication, the dosage of the other medication may require adjustment given the increased rate of metabolism and the reduced effect of the medication.
What happens when someone has poor metabolism Phenotype?
- A poor metabolizing enzyme has very low activity. It is possible to
have side effects even with a very low drug dose because the enzyme is slow to break down the drug. May not be therapeutic or can be out of range.
ex: Plavix - may not work as well and be less effective.
What does the U.S. Food and Drug Administration regulate when it comes to medications?
- The official labeling for all prescription and over the counter drugs -
US food and drug administration is required for medical devices including artificial joints.
Reasons for medication non-adherence:
- Forgetfulness, lack of planning, cost, dissatisfaction, altered dosing. 2 / 3
Black Box Warnings
- The strongest safety warning a drug can carry and still remain on
the market. Text for the warning is presented inside a box with a heavy black border. A warning on drugs with serious or life- threatening risks.
Opioid (BBW)
- Respiratory Depression
Fentanyl (BBW)
- Fatal respiratory depression
Methadone (BBW)
- Prolonged QT interval
Codeine (BBW)
- Respiratory depression at 10% conversion to morphine - especially
in pregnancy.
Hydromorphone/Oxymorphone (BBW)
- Fatal respiratory depression (cannot prescribe longer acting)
APRN's can prescribe what scheduled drugs
- II, III, IV, V - but depends on state and physician guidance.
Who determines and regulates prescriptive authority?
- State law and is regulated by a health professional board as
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determined by each state. (State board of nursing, state board of medicine, state board of pharmacy)