HK Primary Care — Drug Class & MOA Reference by Condition
For FM finals / MRCGP-level recall. Generic names only — check
local HA formulary for actual first-line agent/availability. Doses
omitted here (ask if you want a specific one) — focus is class +
mechanism.
1. Hypertension
| ACE inhibitor |
lisinopril, ramipril, perindopril |
Inhibit ACE → ↓angiotensin II, ↓aldosterone; ↑bradykinin (→ dry
cough) |
| ARB |
losartan, valsartan, irbesartan |
Block AT1 receptor directly; no bradykinin effect → less cough |
| CCB (dihydropyridine) |
amlodipine, nifedipine |
Block L-type Ca²⁺ channels in vascular smooth muscle →
vasodilation |
| CCB (non-dihydropyridine) |
diltiazem, verapamil |
As above + slow AV conduction/↓contractility (avoid with
beta-blocker) |
| Thiazide/thiazide-like diuretic |
hydrochlorothiazide, indapamide |
Inhibit Na⁺-Cl⁻ cotransporter in DCT → natriuresis |
| Beta-blocker |
bisoprolol, atenolol |
Block β1 → ↓HR, ↓contractility, ↓renin release |
NICE-style stepwise: ACEi/ARB first if <55 and non-Black
African/Caribbean; CCB first if ≥55 or Black African/Caribbean
origin.
2. Lipid disorder
| Statin |
atorvastatin, rosuvastatin, simvastatin |
Competitively inhibit HMG-CoA reductase (rate-limiting step in
cholesterol synthesis) → ↑hepatic LDL receptor expression |
| Cholesterol absorption inhibitor |
ezetimibe |
Inhibits NPC1L1 transporter at intestinal brush border →
↓cholesterol absorption |
| Fibrate |
fenofibrate, gemfibrozil |
PPAR-α agonist → ↑lipoprotein lipase activity → ↓triglycerides
mainly |
| PCSK9 inhibitor |
evolocumab, alirocumab |
Monoclonal Ab vs PCSK9 → prevents LDL-receptor degradation → ↑LDL
clearance |
| Bile acid sequestrant |
cholestyramine |
Binds bile acids in gut, ↑hepatic conversion of cholesterol to bile
acids |
3. Diabetes mellitus (T2DM)
| Biguanide |
metformin |
Activates AMPK → ↓hepatic gluconeogenesis, ↑peripheral insulin
sensitivity; no hypoglycaemia alone |
| Sulfonylurea |
gliclazide, glimepiride |
Bind SUR1 on pancreatic β-cell KATP channel → closure →
depolarisation → insulin release |
| DPP-4 inhibitor (“gliptin”) |
sitagliptin, linagliptin |
Inhibit DPP-4 → ↑endogenous incretins (GLP-1/GIP) →
glucose-dependent insulin release |
| SGLT2 inhibitor (“flozin”) |
empagliflozin, dapagliflozin |
Inhibit SGLT2 in PCT → ↓glucose reabsorption → glucosuria; also
cardio/renal-protective |
| GLP-1 receptor agonist |
liraglutide, semaglutide |
GLP-1 agonism → ↑glucose-dependent insulin, ↓glucagon, ↓gastric
emptying, central satiety |
| Thiazolidinedione |
pioglitazone |
PPAR-γ agonist → ↑insulin sensitivity in adipose/muscle/liver |
| Insulin |
various (basal/bolus) |
Direct replacement |
4. URTI (incl. influenza, tonsillitis)
| Neuraminidase inhibitor |
oseltamivir |
Inhibits viral neuraminidase → prevents progeny virion release from
infected cells (influenza only) |
| Penicillin |
phenoxymethylpenicillin (Pen V), amoxicillin |
β-lactam → inhibits transpeptidase (PBP) → blocks bacterial cell
wall synthesis (for confirmed/high-probability GAS tonsillitis) |
| Antipyretic/analgesic |
paracetamol, ibuprofen |
See OA/analgesia section |
Plain common cold: no antibiotics indicated — see prior summary
doc.
6. Gastroenteritis
| Oral rehydration salts |
ORS |
Na⁺/glucose co-transport drives water absorption in gut |
| 5-HT3 antagonist |
ondansetron |
Blocks 5-HT3 receptors centrally (CTZ) and peripherally (vagal
afferents) → antiemetic |
| Dopamine antagonist (prokinetic) |
metoclopramide |
D2 antagonism (crosses BBB → EPS risk) + 5-HT4 agonism →
prokinetic/antiemetic |
| Opioid receptor agonist (gut) |
loperamide |
μ-opioid agonism in gut wall, minimal CNS penetration → ↓peristalsis
(avoid if bloody/febrile diarrhoea) |
| Fluoroquinolone (selected cases) |
ciprofloxacin |
Inhibits bacterial DNA gyrase/topoisomerase IV (for specific
bacterial/traveller’s diarrhoea only) |
7. Allergic rhinitis
| Intranasal corticosteroid |
fluticasone, mometasone |
Local anti-inflammatory — first-line for
moderate-severe/persistent Sx |
| 2nd-gen oral antihistamine |
cetirizine, loratadine, fexofenadine |
Peripheral H1 antagonism, minimal sedation |
| Leukotriene receptor antagonist |
montelukast |
CysLT1 receptor antagonist → ↓leukotriene-mediated inflammation |
| Intranasal antihistamine |
azelastine |
Local H1 antagonism |
| Mast cell stabiliser |
sodium cromoglicate |
Inhibits mast cell degranulation |
8. Dyspepsia / GERD
| PPI |
omeprazole, esomeprazole, lansoprazole |
Irreversibly inhibit H⁺/K⁺-ATPase (proton pump) on gastric parietal
cells |
| H2 receptor antagonist |
famotidine |
Blocks H2 receptors on parietal cells → ↓acid secretion (less potent
than PPI) |
| Antacid |
aluminium/magnesium hydroxide |
Direct acid neutralisation |
| Prokinetic |
domperidone |
Peripheral D2 antagonist (limited BBB crossing → less EPS than
metoclopramide) |
| H. pylori eradication |
PPI + amoxicillin + clarithromycin (metronidazole if
penicillin-allergic) |
Triple therapy — acid suppression + dual antibiotic |
9. Obesity
| Lipase inhibitor |
orlistat |
Inhibits pancreatic/gastric lipase → ↓dietary fat absorption |
| GLP-1 receptor agonist (higher dose) |
liraglutide (Saxenda), semaglutide (Wegovy) |
As above — also central appetite suppression |
10. OA knee / knee complaints
| Paracetamol |
— |
Mechanism incompletely understood; central COX inhibition/other CNS
effects — first-line analgesic |
| Topical NSAID |
diclofenac gel |
Local COX-1/2 inhibition → ↓prostaglandin synthesis, less systemic
exposure |
| Oral NSAID (non-selective) |
ibuprofen, naproxen |
Non-selective COX-1/2 inhibition |
| Oral NSAID (COX-2 selective) |
celecoxib |
Selective COX-2 inhibition → less GI toxicity, ↑cardiovascular
risk |
| Intra-articular corticosteroid |
triamcinolone, methylprednisolone |
Local anti-inflammatory injection |
11. Gout
| NSAID (acute) |
naproxen, indomethacin |
COX inhibition |
| Colchicine (acute) |
colchicine |
Binds tubulin → inhibits microtubule polymerisation → ↓neutrophil
chemotaxis/degranulation |
| Corticosteroid (acute, if NSAID/colchicine CI) |
prednisolone (oral) or intra-articular |
Anti-inflammatory |
| Xanthine oxidase inhibitor (chronic ULT) |
allopurinol, febuxostat |
Inhibit xanthine oxidase → ↓uric acid production |
| Uricosuric (chronic ULT) |
probenecid |
Inhibits renal tubular urate reabsorption → ↑excretion |
Don’t start urate-lowering therapy during an acute flare;
continue if already established.
12. Depressive disorder
| SSRI |
sertraline, fluoxetine, escitalopram |
Inhibit serotonin reuptake transporter (SERT) → ↑synaptic 5-HT |
| SNRI |
venlafaxine, duloxetine |
Inhibit both SERT and NET → ↑5-HT and noradrenaline |
| NaSSA |
mirtazapine |
α2-antagonist (↑NA/5-HT release) + 5-HT2/5-HT3 antagonist —
sedating, appetite-stimulating |
| TCA |
amitriptyline |
Inhibit NA/5-HT reuptake; also anticholinergic/antihistaminic (more
SEs, used at low dose for pain too) |
13. Thyroid disorder
| Thyroid hormone replacement |
levothyroxine (T4) |
Synthetic T4, peripherally converted to active T3 |
| Thionamide (antithyroid) |
carbimazole (prodrug → methimazole) |
Inhibits thyroid peroxidase → blocks iodination/coupling of
thyroglobulin |
| Thionamide (antithyroid) |
propylthiouracil (PTU) |
As above + inhibits peripheral T4→T3 conversion; preferred 1st
trimester pregnancy (less teratogenic, but hepatotoxicity risk) |
| Beta-blocker (symptom control) |
propranolol |
Non-selective β-blockade → controls tremor/palpitations/tachycardia
in thyrotoxicosis |
14. Ischaemic heart disease
| Antiplatelet (COX inhibitor) |
aspirin |
Irreversible COX-1 inhibition → ↓thromboxane A2 → ↓platelet
aggregation |
| Antiplatelet (P2Y12 inhibitor) |
clopidogrel, ticagrelor |
Block ADP-mediated P2Y12 receptor → ↓platelet activation |
| Beta-blocker |
bisoprolol, metoprolol |
↓HR/contractility → ↓myocardial O2 demand |
| Statin |
atorvastatin |
As above — also plaque stabilisation |
| Nitrate |
GTN (sublingual/spray), isosorbide mononitrate |
NO donor → venodilation (↓preload) + coronary vasodilation |
| ACE inhibitor |
ramipril |
Cardioprotective remodelling, esp. post-MI/LV dysfunction |
15. Low back pain
| Paracetamol / NSAID |
as above |
As above — first-line |
| Muscle relaxant (short-term, selected cases) |
diazepam (limited use) |
GABA-A positive allosteric modulation |
Avoid routine opioids for chronic non-specific LBP;
exercise/physio is mainstay.
16. Benign prostatic hyperplasia (BPH)
| α1-blocker |
tamsulosin, doxazosin |
Selective α1A antagonism → relaxes prostatic/bladder neck smooth
muscle (fast symptom relief) |
| 5α-reductase inhibitor |
finasteride, dutasteride |
Inhibit conversion testosterone→DHT → shrinks prostate over months
(slower onset, reduces long-term progression) |
17. Dermatophytosis (tinea)
| Allylamine (topical/oral) |
terbinafine |
Inhibits squalene epoxidase → squalene accumulation (toxic) +
ergosterol deficiency |
| Azole (topical) |
clotrimazole, miconazole |
Inhibit lanosterol 14α-demethylase (CYP450 enzyme) → blocks
ergosterol synthesis |
| Azole (oral, extensive/nail/scalp disease) |
itraconazole, fluconazole |
As above, systemic |
18. Constipation
| Bulk-forming |
ispaghula husk (psyllium) |
↑stool bulk/water retention → mechanical peristaltic stimulus |
| Osmotic |
lactulose, macrogol (PEG) |
Non-absorbable → draws water into lumen osmotically (lactulose also
fermented → mild acidification) |
| Stimulant |
senna, bisacodyl |
Stimulate enteric nerves/colonic motility directly |
| Stool softener |
docusate sodium |
Surfactant — allows water/fat to penetrate stool |
19. Urinary tract infection
| Nitrofuran |
nitrofurantoin |
Bacterial nitroreductases generate reactive intermediates → damage
DNA/ribosomal proteins (multi-target); avoid near-term pregnancy &
significant renal impairment |
| Folate synthesis inhibitor |
trimethoprim |
Inhibits bacterial dihydrofolate reductase |
| Phosphonic acid derivative |
fosfomycin |
Inhibits MurA enzyme → blocks peptidoglycan (cell wall) synthesis;
single-dose regimen |
| β-lactam/β-lactamase inhibitor |
co-amoxiclav |
For resistant/complicated cases |
20. Cerebrovascular disease (stroke/TIA secondary prevention)
| Antiplatelet |
aspirin, clopidogrel |
As above |
| Statin (high-intensity) |
atorvastatin |
As above |
| DOAC (if AF-related) |
apixaban, rivaroxaban (direct Xa inhibitors); dabigatran (direct
thrombin inhibitor) |
Direct inhibition of clotting factor Xa or IIa |
| Vitamin K antagonist |
warfarin |
Inhibits vitamin K epoxide reductase → ↓synthesis of factors II,
VII, IX, X |
21. Vertigo / dizziness
| Histamine analogue |
betahistine |
Weak H1 agonist + H3 antagonist → ↑inner ear blood flow (used in
Ménière’s) |
| Dopamine antagonist (acute vertigo/vomiting) |
prochlorperazine |
D2 antagonism at CTZ + vestibular sedation |
| Antihistamine (vestibular sedative) |
cinnarizine |
H1 antagonism + mild Ca²⁺ channel blockade |
22. Asthma
| SABA (reliever) |
salbutamol |
β2-agonism → bronchodilation |
| ICS (preventer) |
beclometasone, budesonide, fluticasone |
Local anti-inflammatory — reduces airway
inflammation/hyperresponsiveness |
| LABA |
salmeterol, formoterol |
Longer-acting β2-agonism — always combined with
ICS, never alone |
| LTRA |
montelukast |
CysLT1 antagonist |
| LAMA (add-on, severe) |
tiotropium |
Muscarinic (M3) antagonism → bronchodilation |
| Anti-IgE (severe allergic asthma) |
omalizumab |
Monoclonal Ab binds free IgE → prevents mast cell/basophil
activation |
23. Bursitis / tendinitis / synovitis
| NSAID (oral/topical) |
as above |
As above |
| Corticosteroid injection |
triamcinolone |
Local anti-inflammatory |
24. Liver disease
| Nucleos(t)ide analogue (chronic Hep B) |
tenofovir, entecavir |
Inhibit HBV reverse transcriptase/DNA polymerase |
| Aldosterone antagonist (ascites) |
spironolactone |
Mineralocorticoid receptor antagonism → K⁺-sparing diuresis |
| Osmotic laxative (hepatic encephalopathy) |
lactulose |
Traps ammonia as ammonium in gut lumen (acidification) + laxative
effect → ↓ammonia absorption |
| Non-selective beta-blocker (variceal prophylaxis) |
propranolol |
↓cardiac output (β1) + splanchnic vasoconstriction (unopposed α, β2
blockade) → ↓portal pressure |
25. Abdominal pain (functional/IBS-type)
| Antimuscarinic antispasmodic |
hyoscine butylbromide |
Antimuscarinic → relaxes GI smooth muscle; poor oral bioavailability
(mainly peripheral effect) |
| Musculotropic antispasmodic |
mebeverine |
Direct smooth muscle relaxant, minimal anticholinergic effect |
26. Neck / shoulder pain
Same as low back pain — paracetamol/NSAIDs first-line; consider
topical NSAID for localised tendinopathy.
27. Anxiety
| SSRI/SNRI |
as above |
First-line for GAD (same as depression) |
| Benzodiazepine (short-term only) |
diazepam, lorazepam |
Positive allosteric modulator at GABA-A receptor → ↑Cl⁻ conductance;
risk of dependence, avoid long-term |
| 5-HT1A partial agonist |
buspirone |
Non-sedating, non-addictive alternative, slower onset |
| Beta-blocker (somatic/performance anxiety) |
propranolol |
β-blockade → controls tremor/palpitations, no effect on
psychological Sx |
28. Headache
| Simple analgesic (tension-type) |
paracetamol, NSAIDs |
As above |
| Triptan (migraine, acute) |
sumatriptan |
5-HT1B/1D agonism → cranial vasoconstriction + inhibits trigeminal
neuropeptide (CGRP) release |
| Migraine prophylaxis |
propranolol, topiramate, amitriptyline (low dose) |
Propranolol: β-blockade; Topiramate: multiple (Na⁺ channel block,
↑GABA, ↓glutamate); Amitriptyline: as above |
Watch for medication-overuse headache with frequent
analgesic/triptan use.
29. Sleep disturbance
| Z-drug |
zolpidem, zopiclone |
GABA-A receptor agonism (non-benzodiazepine site) — short-term use
only |
| Melatonin |
melatonin |
MT1/MT2 receptor agonism — circadian regulation, useful in
elderly |
CBT-I is first-line; pharmacotherapy is short-term adjunct
only.
30. Eye complaints (blepharitis, stye, chalazion, red eye)
| Topical antibiotic |
chloramphenicol drops/ointment |
Inhibits bacterial 50S ribosomal subunit → blocks protein synthesis
(for bacterial conjunctivitis/infective blepharitis) |
| Topical antihistamine/mast cell stabiliser |
olopatadine, sodium cromoglicate |
For allergic conjunctivitis |
| Warm compress + lid hygiene |
— |
Mainstay for blepharitis/stye/chalazion; antibiotics only if
cellulitis/spreading infection |
31. Osteoporosis
| Bisphosphonate |
alendronate, zoledronic acid |
Bind hydroxyapatite, taken up by osteoclasts → inhibit farnesyl
pyrophosphate synthase → osteoclast apoptosis |
| RANKL inhibitor |
denosumab |
Monoclonal Ab vs RANKL → prevents osteoclast
differentiation/activation |
| PTH analogue (anabolic, severe cases) |
teriparatide |
Intermittent PTH(1-34) exposure → net osteoblast stimulation
(anabolic, unlike continuous PTH) |
| SERM |
raloxifene |
Selective oestrogen receptor modulator — oestrogenic effect on bone,
antagonist on breast/uterus |
| Adjunct |
calcium + vitamin D |
Substrate/cofactor for bone mineralisation |
32. Urticaria
| 2nd-gen antihistamine (may uptitrate to 4× dose) |
cetirizine, fexofenadine |
Peripheral H1 antagonism — first-line |
| Oral corticosteroid (short course, severe/acute) |
prednisolone |
Anti-inflammatory |
| Anti-IgE (chronic spontaneous urticaria, refractory) |
omalizumab |
As above |
33. Haemorrhoids
| Topical corticosteroid + local anaesthetic |
hydrocortisone + lidocaine combo |
Anti-inflammatory + local analgesia (short courses only) |
| Bulk laxative |
ispaghula |
Softens stool, ↓straining |
34. Anaemia
| Iron replacement |
ferrous sulfate, ferrous fumarate |
Replenishes iron stores for haem synthesis |
| B12 replacement |
hydroxocobalamin (IM), cyanocobalamin (oral) |
Cofactor for DNA synthesis/methylation — replacement |
| Folate replacement |
folic acid |
Cofactor for DNA synthesis — replacement |
| Erythropoiesis-stimulating agent (CKD-related) |
erythropoietin (epoetin alfa) |
Stimulates erythroid progenitor cells in bone marrow |
35. Skin infections
| Topical antibiotic (impetigo) |
fusidic acid, mupirocin |
Fusidic acid: inhibits bacterial protein synthesis (EF-G);
Mupirocin: inhibits isoleucyl-tRNA synthetase |
| β-lactam (cellulitis) |
flucloxacillin |
Penicillinase-resistant β-lactam — covers S.
aureus/strep |
| Alternative (penicillin allergy/MRSA risk) |
clindamycin, doxycycline, co-trimoxazole |
Clindamycin: inhibits 50S ribosome; Doxycycline: inhibits 30S
ribosome; Co-trimoxazole: dual folate synthesis blockade |
36. Acute bronchitis
Mostly viral — symptomatic care only (as for URTI). Consider
doxycycline/amoxicillin only if suspected bacterial
superinfection, or in COPD/high-risk patients with purulent sputum +
systemic upset.
37. Herpes zoster
| Nucleoside analogue (antiviral) |
aciclovir, valaciclovir, famciclovir |
Require viral thymidine kinase for activation → inhibit viral DNA
polymerase, chain termination. Start within 72h of rash
onset |
| Neuropathic agent (post-herpetic neuralgia) |
gabapentin, pregabalin, amitriptyline |
See neuropathic pain section below |
38. Chest pain
Not a distinct drug class of its own — management follows the
underlying cause (IHD #14, GERD #8). GTN may be used as
both symptomatic relief and a rough diagnostic pointer toward cardiac
cause (though not definitive).
39. Cough
Follows underlying cause: URTI/bronchitis (#4/#36, mostly
supportive), asthma (#22, consider ICS trial if cough-variant), GERD
(#8, PPI trial if reflux-associated cough).
Bonus — genuinely high-yield in HK primary care but not explicit in
your list
Peripheral/diabetic neuropathy (very common given DM
prevalence)
| Gabapentinoid |
gabapentin, pregabalin |
Bind α2δ subunit of voltage-gated Ca²⁺ channels → ↓excitatory
neurotransmitter release |
| SNRI |
duloxetine |
As above — licensed specifically for diabetic neuropathic pain |
| TCA (low dose) |
amitriptyline |
As above, used off-label for neuropathic pain at lower doses than
antidepressant use |
Immunisation (Preventive category)
| Inactivated (killed) |
injectable influenza, Hep A |
Non-replicating antigen — immune response without infection
risk |
| Live attenuated |
MMR, varicella, live nasal flu |
Weakened live organism — replicates transiently → robust/durable
immunity; avoid in pregnancy/immunosuppression |
| Subunit/recombinant |
Hep B, HPV (recombinant capsid protein), recombinant zoster
(Shingrix-type) |
Purified antigen component only |
| Toxoid |
tetanus, diphtheria |
Inactivated toxin — immunity against toxin, not organism |
| Polysaccharide/conjugate |
pneumococcal (PPSV23 polysaccharide vs PCV13/15/20 conjugate) |
Conjugate linked to carrier protein → T-cell dependent response,
works in young children (polysaccharide alone is T-independent, poor in
<2yo) |
| mRNA |
COVID-19 mRNA vaccines |
mRNA encoding viral antigen (e.g. spike protein) taken up by cells →
transient antigen expression → immune response |
Notes on local practice
This reflects internationally standard drug classes/mechanisms and
largely NICE-consistent first-line reasoning — the pharmacology itself
doesn’t change by jurisdiction. What genuinely can differ in
HK: exact first-line agent per HA Drug Formulary, GOPC prescribing
restrictions (some drug classes are specialist-initiated only in the
public system), and availability of certain newer agents (e.g.,
SGLT2i/GLP-1 agonist access, PCSK9i restrictions) outside private
practice. I don’t have the current HA Drug Formulary to confirm exact
tier/restriction status — worth cross-checking against it directly for
anything formulary-specific in an OSCE/finals context.