AFK Pharmacology Cheat Sheet: The 30 Highest-Yield Drugs

Pharmacology accounts for roughly 14 percent of the AFK blueprint, but its real weight on exam day is heavier. Drug items hide inside operative, periodontology, oral medicine, and emergency stems, and a wrong maximum dose, missed contraindication, or stale prophylaxis indication flips a borderline pass into a fail. This cheat sheet condenses the thirty drugs that recur across released NDEB material into a single reference.

What AFK Pharmacology Tests

The AFK tests a narrow band of clinical decisions: max dose for a paediatric patient, antibiotic for a penicillin-allergic patient with endocarditis risk, analgesic to avoid in third-trimester pregnancy, reversal agent for an over-sedated patient. Five domains carry the weight — local anaesthesia, analgesics, antibiotics, sedation, emergencies. Mechanism matters only enough to justify a clinical choice; doses, interactions, contraindications, and pregnancy categories carry the marks.

Local Anaesthesia: The Top 6 Drugs

Local anaesthesia is the most heavily tested pharmacology subdomain, and dose calculations are the single most common stem format. Memorise the mg/kg cap first, then the cartridge equivalent (1.8 mL of 2 percent = 36 mg; 4 percent = 72 mg).

Agent	Concentration	Vasoconstrictor	Max dose (with vc)	Dental notes
Lidocaine	2%	Epi 1:100,000	7.0 mg/kg, 500 mg	Workhorse infiltration and block; gold standard reference agent
Articaine	4%	Epi 1:100,000/200,000	7.0 mg/kg, 500 mg	Best buccal infiltration for mandibular molars; thiophene ring, ester linker
Mepivacaine	3%	None	6.6 mg/kg, 400 mg	Choice when epi is contraindicated; shortest soft-tissue numbness
Prilocaine	4%	Epi 1:200,000	8.0 mg/kg, 600 mg	Methaemoglobinaemia risk above 600 mg; avoid in G6PD or sickle cell
Bupivacaine	0.5%	Epi 1:200,000	1.3 mg/kg, 90 mg	Long acting; post-surgical analgesia; cardiotoxic in overdose
Benzocaine (topical)	20%	n/a	Topical only	Methaemoglobinaemia in infants; avoid under age 2

Examiners reuse three hooks: why articaine is preferred for buccal infiltration of mandibular molars (thiophene ring, higher lipid solubility, bone diffusion), why mepivacaine 3 percent is used in cardiac patients (no vasoconstrictor required), and which agents carry methaemoglobinaemia risk (prilocaine and benzocaine). Expect a dose calculation every sitting.

Analgesics and NSAIDs

Post-operative analgesia stems pivot on a contraindication. First-line in a healthy adult is ibuprofen 400 to 600 mg q6h; the choice changes the moment the stem mentions pregnancy, peptic ulcer disease, renal impairment, or anticoagulation.

Drug	Mechanism	Key contraindications	Pregnancy
Acetaminophen	Central COX inhibition (CNS)	Hepatic impairment; max 4 g/day, 3 g if hepatic risk	Safe all trimesters
Ibuprofen	Non-selective COX-1/COX-2	PUD, CKD, third trimester, ASA-induced asthma	Avoid third trimester
Naproxen	Non-selective COX-1/COX-2	Same as ibuprofen; longer half-life	Avoid third trimester
Celecoxib	Selective COX-2	Sulfa allergy, CV disease	Avoid third trimester
ASA (aspirin)	Irreversible COX inhibition	Reye syndrome under 16; bleeding risk	Avoid third trimester
Codeine	Opioid (CYP2D6 to morphine)	Children under 12; ultra-rapid metabolisers; OSA	Caution; not preferred
Tramadol	Mu-opioid + SNRI	Seizure history, SSRI co-administration	Caution

The third-trimester rule is a perennial favourite: NSAIDs are contraindicated after 30 weeks (premature ductus closure, oligohydramnios); acetaminophen replaces them. Codeine has been pulled from paediatric formularies in Canada, the UK, and the US — if a stem offers it for a child, that is the wrong answer.

Antibiotics for Dentistry

Antibiotic stems hinge on three decisions: spectrum, allergy status, and prophylaxis indication.

Drug	Class	Dental indication	Allergy / interaction note
Penicillin VK	Beta-lactam	First-line odontogenic infection	Type I hypersensitivity
Amoxicillin	Aminopenicillin	First-line; broader spectrum than Pen VK	Cross-reactivity with cephalosporins (~1%)
Amoxicillin-clavulanate	Aug. aminopenicillin	Resistant or recurrent infections	GI upset; clavulanate adds beta-lactamase coverage
Cephalexin	1st-gen cephalosporin	Penicillin alternative if no anaphylaxis	Avoid in true anaphylaxis to penicillin
Clindamycin	Lincosamide	Penicillin allergy; anaerobes; bone	C. difficile colitis risk; oral lichenoid reactions
Metronidazole	Nitroimidazole	Anaerobes; ANUG; combined with amox in periodontitis	Disulfiram-like reaction with alcohol; potentiates warfarin
Azithromycin	Macrolide	Penicillin allergy; aggressive periodontitis adjunct	QT prolongation; CYP3A4 interactions
Doxycycline	Tetracycline	Aggressive/recurrent periodontitis; sub-antimicrobial dosing	Avoid pregnancy and under age 8; photosensitivity

Two patterns recur. In a stem with "penicillin allergic — anaphylaxis," the safe answer is clindamycin or azithromycin, never a cephalosporin. Metronidazole plus alcohol produces a disulfiram-like reaction (flushing, tachycardia, vomiting), and metronidazole potentiates warfarin enough to require an INR check.

The free AFK diagnostic returns a domain-level breakdown of your pharmacology recall.

Antibiotic Prophylaxis: The AHA 2007 Indications

The AHA 2007 guidance, endorsed by the Canadian Dental Association, narrowed prophylaxis sharply. Prophylaxis is recommended only for the cardiac conditions below, and only before procedures involving manipulation of gingival tissue, the periapical region, or perforation of the oral mucosa.

The four cardiac indications:

1. Prosthetic cardiac valve or prosthetic material used in valve repair.
2. Previous infective endocarditis.
3. CHD — unrepaired cyanotic; repaired with prosthetic material in the first six months; repaired with residual defects at the prosthetic site.
4. Cardiac transplant recipients with valvulopathy.

MVP, rheumatic disease without prosthetic valve, and isolated ASD/VSD/PDA repaired over six months ago are not indications. ADA/AAOS guidance recommends against routine prophylaxis for prosthetic joints.

Scenario	Drug	Adult dose (30–60 min pre-op)
Standard oral	Amoxicillin	2 g PO
Unable to take oral	Ampicillin or cefazolin	2 g IM/IV
Penicillin allergy (no anaphylaxis)	Cephalexin	2 g PO
Penicillin allergy (anaphylaxis)	Clindamycin or azithromycin	600 mg PO / 500 mg PO

The AHA 2021 update removed clindamycin because of C. difficile risk and now favours azithromycin or doxycycline; the AFK has historically tested the 2007 algorithm but candidates should know both exist.

Sedation Agents and Their Reversal

Conscious sedation in dentistry usually means nitrous oxide or oral midazolam. The exam tests onset, offset, and — most often — what to do when sedation goes too far.

Agent	Mechanism	Reversal agent	Reversal dose
Nitrous oxide	NMDA antagonism, GABA potentiation	100% O2	5 minutes post-procedure
Midazolam	GABA-A potentiation (BZD)	Flumazenil	0.2 mg IV q1min, max 1 mg
Diazepam	GABA-A potentiation (BZD)	Flumazenil	Same
Fentanyl/morphine	Mu-opioid agonist	Naloxone	0.4 mg IV/IM, repeat q2–3 min
Diphenhydramine	H1 antagonist (sedating)	Supportive	n/a

Two facts recur: flumazenil reverses benzodiazepines but not opioids; naloxone reverses opioids but not benzodiazepines. Combined sedation may need both. Nitrous oxide carries diffusion hypoxia risk without 3–5 minutes of post-procedure oxygen, and is contraindicated in first-trimester pregnancy, pneumothorax, recent middle-ear surgery, and bowel obstruction.

Drug Interactions to Memorise

The AFK reuses a small set of high-yield drug-drug interactions. If you memorise ten, make them these:

1. Warfarin + metronidazole, fluconazole, or erythromycin — INR rises sharply; bleeding risk.
2. Warfarin + amoxicillin — modest INR elevation; check INR before extractions.
3. MAOI + epinephrine — hypertensive crisis; limit to one cartridge of 1:100,000 epi or use a plain agent.
4. Non-selective beta blocker + epinephrine — unopposed alpha-1 effect, hypertension and reflex bradycardia; limit epi to two cartridges.
5. SSRI + NSAIDs or aspirin — GI bleeding risk increases roughly threefold.
6. Lithium + NSAIDs — reduced renal lithium clearance, toxicity risk.
7. Methotrexate + NSAIDs — reduced renal MTX clearance, marrow suppression.
8. Tetracyclines + dairy, antacids, iron — chelation reduces absorption by up to 80 percent.
9. Clarithromycin/erythromycin + statins — CYP3A4 inhibition raises rhabdomyolysis risk.
10. Tramadol or meperidine + SSRI/SNRI/MAOI — serotonin syndrome.

Two more to hold: metronidazole + alcohol (disulfiram reaction), and acetaminophen with chronic alcohol use (hepatic toxicity below the 4 g/day cap).

Pregnancy and Breastfeeding

Exam stems still use the legacy A/B/C/D/X letter system. The dental short list:

• Safe all trimesters: acetaminophen, penicillins, amoxicillin, cephalosporins, clindamycin, lidocaine with epi.
• Avoid third trimester: all NSAIDs — premature ductus closure.
• Avoid throughout pregnancy: tetracyclines (tooth discolouration), metronidazole and nitrous oxide in the first trimester.
• Lactation: clindamycin, amoxicillin, lidocaine, and acetaminophen are safe. Avoid tetracyclines and high-dose aspirin.

The most-tested item is the third-trimester NSAID rule.

Common Emergencies and First-Line Drugs

Stems are written as if you are the operator. Memorise the first-line drug, dose, and route.

Emergency	First-line drug	Adult dose / route
Anaphylaxis	Epinephrine	0.3–0.5 mg IM 1:1,000, anterolateral thigh; repeat q5–15 min
Acute asthma	Salbutamol (albuterol)	2 puffs MDI, repeat q20 min
Hypoglycaemia (conscious)	Oral glucose 15 g	Juice, gel, or tablets
Hypoglycaemia (unconscious)	Dextrose 50% IV	25 g IV, or glucagon 1 mg IM
Suspected MI	ASA 160–325 mg chewed + nitroglycerin 0.4 mg SL	Repeat nitro q5 min × 3 if no relief
Seizure (>5 min)	Midazolam	10 mg IM/IN/buccal
Syncope	Trendelenburg + O2	Supportive; rule out cardiogenic
Opioid overdose	Naloxone	0.4 mg IV/IM, repeat q2–3 min

The most-tested drug here is epinephrine. Anaphylaxis dosing is 1:1,000 IM; cardiac arrest dosing is 1:10,000 IV — confusing the two is a classic distractor.

The Lumen AFK diagnostic includes a dedicated emergencies block matching dose-pick stems the NDEB reuses across cycles.

Self-Test: 5 Sample MCQs

NDEB style — single best answer, four options, one rationale.

1. A 25 kg child requires a mandibular block with 2 percent lidocaine + 1:100,000 epi. Maximum cartridges (1.8 mL)?

A. 2 cartridges B. 3 cartridges C. 4 cartridges D. 5 cartridges

Answer: C. Max lidocaine with epi is 7 mg/kg (cap 500 mg). 25 × 7 = 175 mg. Each 1.8 mL 2 percent cartridge contains 36 mg. 175 ÷ 36 = 4.86, rounded down to 4.

2. A 58-year-old with a prosthetic mitral valve presents for a routine extraction. She reports a delayed maculopapular rash to amoxicillin (no anaphylaxis). Most appropriate prophylaxis?

A. Amoxicillin 2 g PO 30 minutes pre-op B. Cephalexin 2 g PO 30 minutes pre-op C. Clindamycin 600 mg PO 30 minutes pre-op D. No prophylaxis required

Answer: B. Prosthetic valve is an AHA indication. Delayed non-IgE rash is not anaphylaxis, so a first-gen cephalosporin is acceptable. Clindamycin is reserved for true anaphylaxis.

3. A 32-week pregnant patient develops post-extraction pain. Most appropriate analgesic?

A. Ibuprofen 600 mg q6h B. Naproxen 500 mg q12h C. Acetaminophen 1000 mg q6h D. Aspirin 650 mg q4h

Answer: C. All NSAIDs are contraindicated in the third trimester (premature ductus closure, oligohydramnios). Acetaminophen is safe in all trimesters.

4. A patient on warfarin (INR 2.4) needs an antibiotic for odontogenic infection. Which carries the highest bleeding risk via INR elevation?

A. Cephalexin B. Clindamycin C. Metronidazole D. Azithromycin

Answer: C. Metronidazole inhibits CYP2C9 and produces clinically significant INR elevation within 48–72 hours. Cephalexin and clindamycin have minimal warfarin interaction.

5. A patient receiving IV midazolam becomes unresponsive with shallow respirations. First-line reversal?

A. Naloxone 0.4 mg IV B. Flumazenil 0.2 mg IV C. Epinephrine 0.3 mg IM D. Atropine 0.5 mg IV

Answer: B. Flumazenil is the benzodiazepine antagonist; 0.2 mg IV, repeated q1 min up to 1 mg. Naloxone reverses opioids, not benzodiazepines. Always pair reversal with airway support and oxygen.

For thirty more items in the same format, see AFK released questions and the biomedical study guide.

How to Use This Cheat Sheet

Drill these tables in three passes — cold, then after reading Goodman & Gilman or the ADA Drug Therapy Manual on the same agent, then inside timed mocks. Recognising "32 weeks pregnant" or "prosthetic valve" as the pivot is the skill the AFK is scoring. Pair this guide with our pharmacology mnemonics and the 6-month plan to pass the AFK. The free AFK diagnostic tests recall under exam conditions; pricing covers full-bank access.

FAQ

What is the maximum lidocaine dose with epinephrine? Seven mg/kg, capped at 500 mg total. For a 70 kg adult that is 490 mg, or about 13.6 cartridges of 2 percent lidocaine.

Which antibiotics are recommended for AHA endocarditis prophylaxis? Amoxicillin 2 g PO is first-line. Cephalexin 2 g PO covers non-anaphylactic penicillin allergy. Clindamycin 600 mg PO or azithromycin 500 mg PO is used for true anaphylaxis; the 2021 update prefers azithromycin or doxycycline.

Are NSAIDs safe in the third trimester of pregnancy? No. All NSAIDs are contraindicated after roughly 30 weeks because of premature ductus closure, oligohydramnios, and neonatal renal impairment. Acetaminophen replaces them.

What is the difference between articaine and lidocaine? Both are amide LAs at 7 mg/kg max. Articaine has a thiophene ring and an extra ester linkage, giving greater lipid solubility and bone diffusion — reliable mandibular molar anaesthesia by buccal infiltration. It is metabolised primarily in plasma, shortening its half-life.

Why is mepivacaine 3 percent used in cardiac patients? No vasoconstrictor, so it works when epinephrine is undesirable — uncontrolled hypertension, recent MI, severe arrhythmia, non-selective beta blocker or MAOI interaction. Trade-off: shorter pulpal duration.

Can you give epinephrine to a patient on a non-selective beta blocker? Yes, cautiously. Limit to two cartridges of 1:100,000 epi and monitor BP. Unopposed alpha-1 stimulation can cause hypertension with reflex bradycardia. Cardioselective beta blockers carry far less risk.

What dose of epinephrine is given in anaphylaxis versus cardiac arrest? Anaphylaxis: 0.3–0.5 mg of 1:1,000 IM into the anterolateral thigh, repeated q5–15 min. Cardiac arrest: 1 mg of 1:10,000 IV q3–5 min during ACLS. The concentrations are not interchangeable.

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For domain breakdowns, browse the Lumen blog or sit a free AFK exam diagnostic. References: Goodman & Gilman 14th ed., the AHA 2007 IE guideline, the ADA Drug Therapy Manual, and the Health Canada Drug Product Database.