Basic Pharmacology and Drug Classifications

Pharmacology is a critical component of the DOH (UAE) nursing examination. Registered nurses in the UAE administer, monitor, and educate patients about medications across all clinical settings — from emergency departments to outpatient clinics. A thorough understanding of pharmacokinetics (how the body affects a drug), pharmacodynamics (how a drug affects the body), common drug classifications, and medication safety principles is essential. The UAE’s diverse patient population means nurses must also be aware of genetic variations in drug metabolism and the high prevalence of certain conditions (diabetes, hypertension, cardiovascular disease) that require specific medication knowledge.

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🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Pharmacokinetics — ADME:

Phase	What Happens	Clinical Relevance
Absorption	Drug enters bloodstream	Route matters; first-pass metabolism reduces oral bioavailability
Distribution	Drug spreads through body compartments	Protein binding; blood-brain barrier; fat solubility
Metabolism	Drug chemically changed (liver)	Enzyme induction/inhibition; prodrugs activated
Excretion	Drug eliminated (kidneys, liver, lungs)	Renal/hepatic impairment = dose adjustment

Key Pharmacodynamic Concepts:

• Agonist — activates receptor → produces effect
• Antagonist — blocks receptor → prevents agonist effect
• Therapeutic Index (TI) — ratio of toxic dose to effective dose; narrow TI drugs (warfarin, digoxin, lithium) require close monitoring

Most Common Drug Classes in UAE Nursing:

Class	Example	Key Nursing Point
Antibiotics	Amoxicillin, ciprofloxacin	Complete full course; allergy assessment
Antihypertensives	Amlodipine, enalapril	Monitor BP; orthostatic hypotension risk
Antidiabetics	Metformin, insulin	Monitor glucose; timing with meals
Anticoagulants	Heparin, enoxaparin	Bleeding risk; monitor aPTT/INR
Analgesics	Paracetamol, morphine	Pain score; respiratory depression with opioids
PPIs	Omeprazole	IV must be slow; long-term B12 deficiency risk

⚡ Exam Tip: Always check for drug allergies BEFORE administering any medication. This is non-negotiable practice in the UAE. If a patient has an allergy to penicillin, cross-reactivity with cephalosporins is ~1–2% (low but present); avoid unless no alternative and benefit outweighs risk.

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

1. Routes of Drug Administration and Absorption

Oral (PO):

• Most common; safest and most convenient
• Bioavailability (F) = fraction of drug that reaches systemic circulation
• First-pass effect: Drugs absorbed from GI tract pass through liver before reaching systemic circulation — reduces bioavailability (e.g., morphine has significant first-pass effect)
• Enteric-coated tablets: Designed to dissolve in intestine, not stomach — do NOT crush or chew
• Sublingual/Buccal: Absorbed directly into systemic circulation (bypasses first-pass); nitroglycerine (sublingual) for angina

Parenteral (Injection):

• IV: Immediate effect; no absorption phase; highest bioavailability
• IM: Absorption via muscle vasculature; slower than IV; suitable for depot formulations
• SC: Absorption slower than IM; used for insulin, vaccines, some hormones
• ID: Absorption slowest; used for allergy tests, TB skin test

Inhalation: Beta-agonists (salbutamol), corticosteroids (budesonide), anaesthetic gases — used extensively in UAE for asthma/COPD.

Topical: Creams, ointments, patches — transdermal patches allow controlled, sustained drug release (e.g., fentanyl patches, nicotine patches, hormone patches).

2. Drug Interactions

Pharmacokinetic Interactions:

• Absorption: Antacids chelate tetracyclines, fluoroquinolones → reduce absorption; separate by 2 hours
• Distribution: Warfarin binds to albumin; NSAIDs displace warfarin → increased free warfarin → increased bleeding risk
• Metabolism (CYP450 system): Many drugs induce or inhibit liver enzymes:
  • Inducers (↑ enzyme activity → ↓ drug effect): Rifampicin, carbamazepine, phenytoin, St. John’s Wort
  • Inhibitors (↓ enzyme activity → ↑ drug effect): Erythromycin, ciprofloxacin, ketoconazole, grapefruit juice
• Excretion: Probenecid blocks renal secretion of penicillin → increases penicillin levels

Pharmacodynamic Interactions:

• Synergism: Two drugs with similar effects produce greater effect (e.g., benzodiazepines + alcohol = CNS depression)
• Antagonism: One drug opposes the other (e.g., naloxone opposes opioid effect)

Herb-Drug Interactions (Common in UAE):

• Garlic, ginger, ginkgo → increase bleeding risk with anticoagulants
• St. John’s Wort → induces CYP450 → reduces plasma concentrations of many drugs including warfarin, oral contraceptives, antidepressants
• Black cohosh → may worsen liver function

3. Adverse Drug Reactions (ADRs)

Classification:

Type	Mechanism	Examples	Onset
Type A (Augmented)	Predictable; dose-dependent	Digoxin toxicity, hypoglycaemia from insulin	Predictable
Type B (Bizarre)	Unpredictable; not dose-related	Anaphylaxis, drug allergy, idiosyncratic reactions	Unpredictable
Type C (Chronic)	Long-term use	Osteoporosis from corticosteroids	Delayed
Type D (Delayed)	Carcinogenesis, teratogenesis	Thalidomide → phocomelia	Years later
Type E (End of use)	Withdrawal on cessation	Benzodiazepine withdrawal	After stopping

Anaphylaxis — Immediate Recognition and Management:

• Signs: Urticaria, angioedema, bronchospasm (wheezing), hypotension, tachycardia, GI symptoms
• Management: Adrenaline IM (1:1000, 0.01 mg/kg, max 0.5 mg) → Antihistamine IV → Corticosteroid IV → IV fluids → Bronchodilators → Monitor
• In UAE: Every clinic and ward has emergency anaphylaxis kits; know your facility’s location

4. Special Populations

A. Renal Impairment

• Many drugs are renally excreted (e.g., digoxin, gentamicin, metformin)
• Dose adjustment required; check eGFR before administering
• Nephrotoxic drugs: Aminoglycosides, NSAIDs, contrast media, vancomycin

B. Hepatic Impairment

• Liver metabolises most drugs; liver failure = reduced metabolism
• Drugs to avoid: Sedatives, opioid analgesics (can precipitate hepatic encephalopathy)
• Monitor: LFTs, albumin, PT/INR (synthesis function)

C. Elderly

• Altered pharmacokinetics: ↓ renal function, ↓ hepatic blood flow, ↓ body water, ↑ body fat (drugs accumulate in fat)
• Polypharmacy (multiple medications) increases interaction risk
• Increased sensitivity to anticoagulants, sedatives, diuretics
• Increased risk of falls from antihypertensives and sedatives

D. Pregnancy and Lactation

• Most drugs cross the placenta; risk is highest in first trimester
• FDA pregnancy categories (old system; newer system uses narrative description):
  • A: Safe; B: Animal studies no risk / human data reassuring; C: Risk cannot be ruled out; D: Evidence of risk; X: Contraindicated
• Many drugs cross into breast milk — check compatibility before nursing mothers take any new medication

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🔴 Extended — Deep Study (3m+)

Comprehensive coverage for students on a longer study timeline.

5. Antibiotics — Core Principles for UAE Practice

UAE Antibiotic Resistance Crisis:

• UAE, like other Gulf countries, faces significant antibiotic resistance (ESBL-producing Enterobacteriaceae, MRSA, CRE)
• Over-the-counter antibiotics were historically available in some countries — UAE has tightened regulations
• Antimicrobial stewardship programmes are active in all UAE hospitals

Key Antibiotic Classes:

Class	Mechanism	Examples	Nursing Points
Penicillins	Cell wall synthesis inhibitor	Amoxicillin, piperacillin-tazobactam (Zosyn)	Allergy cross-reactivity; monitor for C. difficile
Cephalosporins	Cell wall synthesis inhibitor	Ceftriaxone, cefotaxime	Associated with C. difficile; biliary sludge (ceftriaxone)
Fluoroquinolones	DNA gyrase inhibitor	Ciprofloxacin, levofloxacin	Tendon rupture risk; QT prolongation; avoid in children
Aminoglycosides	Protein synthesis inhibitor	Gentamicin, amikacin	Nephrotoxic and ototoxic; monitor levels; once-daily dosing
Macrolides	Protein synthesis inhibitor	Azithromycin, erythromycin	GI upset; QT prolongation; CYP3A4 inhibition
Glycopeptides	Cell wall synthesis inhibitor	Vancomycin	Red man syndrome (histamine release with rapid IV); nephrotoxic
Carbapenems	Cell wall synthesis inhibitor	Meropenem, imipenem	Last-resort for resistant infections; monitor seizures
Tetracyclines	Protein synthesis inhibitor	Doxycycline	Photosensitivity; avoid in pregnancy; chelation with dairy

Vancomycin — Critical Drug in UAE:

• Reserved for MRSA, C. difficile, resistant Gram-positive infections
• Monitor trough levels (10–15 μg/mL for most infections; 15–20 for pneumonia/osteomyelitis)
• Nephrotoxic (check baseline and periodic creatinine)
• Red man syndrome: Prevent by infusing slowly over 60–120 minutes; pre-medicate with antihistamine if history

6. Anticoagulants

Heparin (Unfractionated):

• Mechanism: Potentiates antithrombin III → inactivates thrombin and Factor Xa
• Monitoring: aPTT (target 1.5–2.5× control)
• Antidote: Protamine sulphate (1 mg per 100 units heparin)
• Complications: HIT (heparin-induced thrombocytopenia — paradoxically causes thrombosis, not bleeding), bleeding

Low Molecular Weight Heparin (LMWH) — Enoxaparin:

• More predictable pharmacokinetics; no routine monitoring
• Anti-Xa levels if needed (e.g., renal impairment, obesity, pregnancy)
• Antidote: Protamine (partial reversal — reverses about 60%)

Warfarin:

• Vitamin K antagonist; inhibits synthesis of factors II, VII, IX, X
• Monitoring: INR (target 2–3 for most indications; 2.5–3.5 for mechanical heart valves)
• Many drug interactions (CYP450); fixed dosing not possible
• Antidote: Vitamin K (IV or oral); FFP or prothrombin complex concentrate for urgent reversal
• Bridging with heparin when initiating warfarin (takes 2–3 days to achieve therapeutic effect)

Direct Oral Anticoagulants (DOACs):

• Apixaban, rivaroxaban, dabigatran, edoxaban
• Target specific clotting factors (Xa or thrombin)
• No routine monitoring needed; predictable pharmacokinetics
• Contraindicated in severe renal impairment
• Antidotes: Idarucizumab (dabigatran), andexanet alfa (apixaban/rivaroxaban)

Exam Watch: DOH examiners frequently ask about the difference between heparin and warfarin, and the concept of bridging. When starting warfarin, it takes 2–3 days to become effective — heparin is continued until INR is therapeutic for 2 consecutive days. Never give both drugs at the same time without a specific bridging protocol.

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