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Schedule I substances such as heroin and LSD have a high abuse potential and no currently accepted medical use, so they cannot be prescribed. Schedules II through V all include drugs with accepted medical uses, with abuse potential decreasing as the schedule number rises.
Unopened insulin vials are kept refrigerated between 2 and 8 degrees C until first use, which preserves potency through the labeled expiration date. Insulin is a protein and is destroyed by freezing, excessive heat, and light exposure.
Coumadin is the brand name for warfarin, an oral vitamin K antagonist anticoagulant. Recognizing brand-generic pairs helps prevent dispensing errors and supports interchange counseling.
A sublingual tablet dissolves under the tongue and is absorbed into the venous plexus, entering the systemic circulation without passing through the liver first. Swallowed dosage forms are absorbed from the GI tract into the portal vein and undergo first-pass metabolism.
Aged cheeses are high in tyramine, which is normally broken down by monoamine oxidase. When that enzyme is inhibited, tyramine accumulates and can trigger a hypertensive crisis. Fresh, low-tyramine foods are appropriate.
Protamine sulfate binds heparin directly and neutralizes its anticoagulant effect. It is the standard reversal agent for unfractionated heparin, though it only partially reverses low molecular weight heparins.
Twenty-four hours represents four half-lives (24 divided by 6), and the fraction remaining is one-half raised to the fourth power, or 1/16. That equals 6.25% of the original amount.
Insulin is a high-alert medication because errors in dose or formulation can cause serious harm, so it requires independent double checks and concentrated formulation safeguards. Common non-high-alert products such as acetaminophen, docusate, and ferrous sulfate do not carry the same risk profile.
The total daily dose is 15 mg/kg multiplied by 20 kg, or 300 mg per day. Dividing that daily total by three doses gives 100 mg per dose.
Lisinopril is an ACE inhibitor and losartan is an angiotensin II receptor blocker; using both blocks the same renin-angiotensin system pathway and risks hyperkalemia and renal injury. Therapeutic duplication is identified by matching mechanism rather than by matching drug names.
ACE inhibitors block the conversion of angiotensin I and also reduce bradykinin breakdown, and accumulated bradykinin is thought to cause the dry cough. Switching to an angiotensin receptor blocker usually resolves it because ARBs do not affect bradykinin.
Simvastatin is metabolized mainly by CYP3A4, and grapefruit juice inhibits that enzyme, raising statin concentrations and the risk of myopathy and rhabdomyolysis. Counseling should include avoiding grapefruit or choosing a statin with a different metabolic pathway.
Isotretinoin causes severe birth defects, so its prescribing program requires pregnancy testing, documented contraception, and regular monitoring before and during therapy. Acetaminophen, penicillin, and insulin are commonly used in pregnancy when clinically indicated.
Flumazenil is a competitive benzodiazepine receptor antagonist that can reverse benzodiazepine-induced sedation. It must be used cautiously because it can precipitate seizures in patients who are benzodiazepine dependent.
Acetylcysteine replenishes glutathione stores and detoxifies the reactive metabolite NAPQI that accumulates when acetaminophen overwhelms normal metabolic pathways. It is most effective when administered soon after ingestion.
Sublingual nitroglycerin is volatile and degrades with exposure to light, heat, and moisture, so it should remain in the original tightly closed dark glass container with the cotton removed. It should be replaced about every six months after opening.
Metronidazole inhibits CYP2C9, the enzyme that metabolizes warfarin, so warfarin levels rise and the INR increases, raising bleeding risk. Enzyme inducers and binding resins tend to lower warfarin effect instead.
Multiply the volume by the drop factor, then divide by the time in minutes: 1,000 mL times 15 drops/mL equals 15,000 drops, and 8 hours equals 480 minutes. The result is about 31 drops per minute.
Hydralazine and hydroxyzine have similar spellings and pronunciation but completely different indications, one for blood pressure and one for allergy or anxiety. Confusion between them can lead to serious dosing errors, so tall-man lettering and auxiliary labels are used.
Opioids slow GI motility and routinely cause constipation that does not resolve with continued use, so a scheduled stimulant laxative is started at the same time as the opioid. Diarrhea is not an expected effect that requires prophylaxis.
Iodinated contrast can cause acute kidney injury, which impairs metformin clearance and allows the drug to accumulate, raising the risk of lactic acidosis. Metformin is typically held at the time of the study and restarted after renal function is confirmed to be acceptable.
Fluoroquinolones such as ciprofloxacin carry a boxed warning for tendinitis and tendon rupture, especially in older adults and patients on corticosteroids. Patients should report tendon pain and stop the drug pending evaluation.
NSAIDs such as ibuprofen inhibit platelet function and irritate the gastric mucosa, and combined with warfarin they substantially increase bleeding risk. Acetaminophen is the preferred analgesic at recommended doses, with monitoring of the INR.
Levothyroxine is taken on an empty stomach 30 to 60 minutes before breakfast because food, calcium, and iron reduce its absorption. Separating the dose from those products by at least four hours keeps thyroid hormone levels stable.
Insulin lispro is a rapid-acting analog with an onset of roughly 15 minutes, so it is injected just before meals. Regular insulin begins working in about 30 minutes, while NPH and glargine are intermediate and long-acting basal products.
Proton pump inhibitors reduce gastric acid secretion by irreversibly blocking the hydrogen-potassium ATPase pump in parietal cells. Omeprazole is the prototype PPI. Ranitidine is an H2 receptor antagonist, while ondansetron and metoclopramide have antiemetic mechanisms.
Short-acting beta-2 agonists relax bronchial smooth muscle within minutes and are used as rescue therapy for acute asthma symptoms. Albuterol is the standard short-acting beta-2 agonist. The other agents are controllers or long-acting bronchodilators.
Loop diuretics inhibit the sodium-potassium-2 chloride cotransporter in the thick ascending limb of the loop of Henle. Furosemide is the prototype loop diuretic. Spironolactone is potassium-sparing, hydrochlorothiazide is a thiazide, and acetazolamide is a carbonic anhydrase inhibitor.
Naloxone is a short-acting opioid receptor antagonist that rapidly reverses opioid-induced respiratory depression. Naltrexone is a longer-acting oral antagonist used mainly for maintenance treatment of dependence, not acute overdose. Flumazenil reverses benzodiazepines, and atropine is an anticholinergic.
Schedule II includes drugs with high abuse potential and accepted medical use but severe dependence liability. Oxycodone is a Schedule II opioid. Alprazolam, lorazepam, and phenobarbital are Schedule IV controlled substances.
Oral suspensions contain dispersed drug particles that settle during storage, so shaking resuspends them and ensures a uniform dose. The other labels apply only to specific products and are not universal for suspensions.
Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis. Atorvastatin belongs to this class. Amlodipine is a calcium channel blocker, atenolol is a beta blocker, and losartan is an angiotensin receptor blocker.
Benzodiazepines enhance inhibitory neurotransmission at GABA-A receptors. Lorazepam is a benzodiazepine used for anxiety, seizures, and sedation. Bupropion is an atypical antidepressant, sertraline is an SSRI, and haloperidol is a typical antipsychotic.
St. John's wort is a potent inducer of CYP3A4 and P-glycoprotein, which can lower warfarin concentrations and reduce the INR. Ginkgo and garlic are more often associated with additive bleeding risk rather than enzyme induction.
Metformin is eliminated renally, and reduced kidney function can lead to drug accumulation and lactic acidosis. The estimated glomerular filtration rate guides whether metformin should be continued, reduced, or avoided.
Digoxin binds to the sodium-potassium ATPase and competes with potassium. Low serum potassium increases digoxin binding and the risk of toxicity, so potassium should be maintained in the normal range.
Food, calcium, and iron can reduce levothyroxine absorption. Administering it on an empty stomach 30 to 60 minutes before breakfast provides the most consistent absorption.
Tetracyclines, including doxycycline, can accumulate in skin and cause phototoxic reactions after sun exposure. Patients should use sunscreen and protective clothing. The other medications are not classic photosensitizers.
Metoclopramide is a dopamine antagonist that can cause tardive dyskinesia, especially with prolonged use. The FDA requires a boxed warning describing this irreversible movement disorder.
Sodium and lithium compete for renal reabsorption. A low-sodium diet increases lithium retention and toxicity risk, while large sodium loads can lower lithium levels. Consistent sodium intake helps stabilize lithium concentrations.
Sildenafil and nitrates both produce vasodilation through the nitric oxide pathway. Combining them can cause life-threatening hypotension, so nitrates are contraindicated with PDE5 inhibitors.
Clozapine can cause severe neutropenia and agranulocytosis. A risk evaluation and mitigation strategy requires regular absolute neutrophil count monitoring to detect this adverse effect early.
Tetracycline chelates with calcium, iron, magnesium, and aluminum, forming complexes that are poorly absorbed. It should be taken on an empty stomach and separated from dairy products and mineral supplements.
Insulin glargine forms microprecipitates after injection and provides a relatively steady basal insulin effect over approximately 24 hours. Lispro and aspart are rapid-acting, and regular insulin is short-acting.
Apixaban directly inhibits factor Xa and is classified as a direct oral anticoagulant. Warfarin is a vitamin K antagonist, heparin works indirectly through antithrombin, and clopidogrel is an antiplatelet agent.
Metformin is contraindicated when the eGFR is below 30 mL/min/1.73 m² because reduced clearance increases the risk of lactic acidosis. Alternative antihyperglycemic therapy should be selected.
For a markedly elevated INR without bleeding, warfarin should be held and low-dose oral vitamin K given to lower the INR. Fresh frozen plasma is reserved for serious or life-threatening bleeding.
Primaquine is an oxidant drug that can cause severe hemolytic anemia in patients with G6PD deficiency. Other oxidant agents such as certain sulfonamides and dapsone should also be avoided.
Tramadol inhibits serotonin reuptake in addition to its opioid activity. Combining it with an SSRI increases serotonergic stimulation and the risk of serotonin syndrome.
Vancomycin has a narrow therapeutic window and can cause nephrotoxicity and ototoxicity. Serum trough or AUC monitoring is used to keep concentrations in the effective but safe range.