EMS Pharmacology: Brightspace Exam Review, Toxidromes & Dosage Calculations

Anaphylaxis

Life-threatening systemic allergic reaction: airway swelling, wheezing, hypotension, hives; IM epinephrine is first-line.

Tachyphylaxis

Rapid loss of drug response after repeated doses over a short period.

Agonist vs antagonist

Agonist activates a receptor (e.g., morphine at opioid receptors); antagonist blocks receptor activity (e.g., naloxone).

Synergism

Two drugs together produce a greater effect than expected from adding their individual effects.

Summation/additive effect

Combined effect equals the sum of individual effects (1 + 1 = 2).

Potentiation

One drug increases another drug's effect, even if the first has little/no effect by itself.

Cumulative effect

Drug accumulates when repeat dosing outpaces elimination, raising toxicity risk.

Cross-tolerance

Tolerance to one drug reduces response to another drug with similar action.

Idiosyncratic reaction

Unusual, unpredictable response specific to an individual.

Therapeutic index

Ratio of toxic dose to effective dose; narrow index = small safety margin.

Therapeutic level

Drug concentration in the effective, acceptably safe range.

Onset / peak / duration

Onset = when effect begins; peak = strongest effect; duration = how long effect lasts.

Half-life

Time for blood/plasma drug concentration to decrease by half.

Generic vs brand/trade

Generic is standardized drug name; brand and trade are two names for the marketed product (e.g., acetaminophen = Tylenol).

Why drugs become OTC

Regulators may permit nonprescription sale when a drug has an acceptable safety profile and clear labeling for self-use.

Pill / tablet / caplet / capsule

Pill = informal term; tablet = compressed solid; caplet = capsule-shaped tablet; capsule = medication inside a dissolvable shell.

Storage

Follow manufacturer temperature, light and moisture requirements; check expiration and integrity.

Discarding medication

Follow agency policy and drug-waste rules. Never put loose needles in trash: sharps container.

Opioids toxidrome

Slow/absent respirations, reduced consciousness, often pinpoint pupils; provide airway/ventilation support and naloxone when indicated.

Benzodiazepines toxidrome

Sedation, ataxia, slurred speech; act by enhancing GABA-A inhibitory signaling.

Barbiturates toxidrome

Profound CNS/respiratory depression, hypotension; increase GABA-A chloride channel opening duration.

Amphetamines/stimulants toxidrome

Agitation, tachycardia, hypertension, sweating, dilated pupils, hyperthermia, seizures.

Alcohol toxidrome

Slurred speech, ataxia, altered mental status, possible hypoglycemia and respiratory depression.

Cannabis toxidrome

Anxiety, altered perception, tachycardia; usually supportive care, but assess for co-ingestion or medical emergencies.

Class I - sodium-channel blockers

Slow rapid sodium influx in cardiac cells.

Class II - beta blockers

Reduce heart rate, AV conduction and contractility.

Class III - potassium-channel blockers

Amiodarone (also blocks sodium/calcium channels and beta receptors); prolongs repolarization/refractory period.

Class IV - calcium-channel blockers

Diltiazem (Cardizem) and verapamil slow AV nodal conduction; can lower HR, BP and contractility.

Digoxin/digitalis

Increases contractility and slows AV nodal conduction; narrow therapeutic index, toxicity/arrhythmia risk.

Chronotropic / inotropic / dromotropic

Chronotropy = heart rate; inotropy = strength of contraction; dromotropy = conduction speed, especially through AV node.

Preload / stroke volume / cardiac output

Preload = ventricular filling/stretch; stroke volume = blood pumped per beat; cardiac output = heart rate x stroke volume.

Alpha-1

Vasoconstriction, raising peripheral vascular resistance/BP (e.g., norepinephrine).

Beta-1

Increases heart rate, contractility and AV conduction; beta blockers oppose these effects.

Beta-2

Bronchodilation (e.g., albuterol) and some vascular smooth muscle relaxation.

Sympathomimetic

Mimics fight-or-flight (epinephrine, albuterol); sympatholytic blocks sympathetic effects (metoprolol).

Parasympathomimetic

Mimics rest-and-digest, slows HR and increases secretions (e.g., pilocarpine); parasympatholytic blocks muscarinic effects (atropine, ipratropium).

Analgesic vs anesthetic

Analgesic reduces pain; anesthetic reduces sensation (local or general), sometimes consciousness.

Renin / angiotensin I / ACE / angiotensin II

Renin starts conversion of angiotensinogen to angiotensin I; ACE converts I to II; angiotensin II causes vasoconstriction and stimulates aldosterone, increasing salt/water retention.

ACE inhibitors

Lisinopril, enalapril (often -pril): reduce angiotensin II and BP; adverse effects include cough, hyperkalemia, hypotension and angioedema.

Peptic ulcer treatment

Proton-pump inhibitors (omeprazole, pantoprazole) are commonly used; H2 blockers (famotidine) also reduce acid.

Avoid/caution with ulcers

Aspirin and other NSAIDs (ibuprofen, ketorolac) increase GI irritation and bleeding risk; check specific contraindications.

Bronchoconstriction/asthma

Inhaled beta-2 agonists such as albuterol relax bronchial smooth muscle; ipratropium blocks muscarinic bronchoconstriction; severe anaphylaxis requires IM epinephrine.

CHF/pulmonary edema

Assess oxygenation and ventilation; CPAP may help if appropriate. Nitroglycerin may reduce preload/BP if indicated and not contraindicated.

Erectile dysfunction (ED) medications

Sildenafil (Viagra), tadalafil (Cialis), vardenafil are PDE-5 inhibitors.

Shortest half-life / rapid push

Adenosine has an extremely short half-life (seconds) and is administered as a rapid IV push with flush for appropriate regular SVT.

Digitalis caution

Digoxin has a narrow therapeutic index and can cause dangerous dysrhythmias; not generally administered for acute rate control in the ambulance.

Organophosphate poisoning

Cholinesterase inhibition causes excessive acetylcholine. SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis.

Treatment for organophosphate poisoning

PPE/decontamination and airway suction/ventilation; atropine to reverse muscarinic effects, pralidoxime (2-PAM) to reactivate cholinesterase when indicated, benzodiazepines for seizures, per protocol.

Tricyclic antidepressant overdose

Amitriptyline, nortriptyline: anticholinergic findings, seizures, hypotension, widened QRS and ventricular dysrhythmias.

Schedule I

Federal category with no currently accepted medical use under federal law and high abuse potential; heroin is an example.

Schedule II

High abuse potential with accepted medical use, e.g., fentanyl, morphine, oxycodone.

Schedule III

Lower abuse potential than I/II, e.g., ketamine, certain codeine combinations.

Schedule IV

Lower abuse potential than III, e.g., diazepam, lorazepam, alprazolam.

NSAIDs

Nonsteroidal anti-inflammatory drugs inhibit COX/prostaglandin production, reducing pain, inflammation and fever. Examples: ibuprofen, naproxen, aspirin, ketorolac.

Medication calculations - drops/minute (gravity)

(Volume in mL x drop factor in gtt/mL) / time in minutes = gtt/min.

Infusion pump

mL/hr = total volume (mL) / time (hours).

Drug concentration

mg/mL = drug amount (mg) / total solution volume (mL). For mcg/mL, multiply mg by 1,000 before dividing by mL.

Weight-based drip (mcg/kg/min)

mL/hr = [ordered mcg/kg/min x weight (kg) x 60] / concentration (mcg/mL).

Safety

Check units, concentration, weight, pump/drip set, clinical appropriateness and local protocol.