2nd Year MBBS Pharmacology - Short Note Answers

a. SERMs: Enumeration, Mechanism of Action & Indications of Two

Enumeration of SERMs

Mechanism of Action

• Estrogen normally binds ER → receptor-DNA complex → gene transcription → cell response
• SERMs competitively bind the same ER
• In some tissues (e.g., bone), the SERM-ER complex recruits agonist coactivators → estrogen-like effect
• In other tissues (e.g., breast), the SERM-ER complex recruits corepressors → anti-estrogen effect
• This tissue selectivity is due to differences in coregulator expression and the conformational change each SERM induces in the ER

1. Tamoxifen - In Detail

• Competitive antagonist at ER in breast tissue - blocks estrogen-driven tumor cell proliferation
• Acts as a partial agonist in bone, endometrium, and cardiovascular tissue

• Effective orally; metabolized by liver (metabolites like endoxifen are more potent)
• Inhibits CYP3A4 and P-glycoprotein
• Excreted via bile into feces

• First-line therapy for estrogen receptor (ER)-positive breast cancer (hormone-sensitive)
• Prevention of breast cancer in high-risk women
• Adjuvant therapy post-surgery for breast carcinoma

• Hot flashes, nausea, vaginal bleeding/discharge
• Risk of endometrial cancer (due to agonist activity in endometrium)
• Thromboembolism (DVT, pulmonary embolism)
• Ocular toxicity (cataracts, retinopathy with long-term use)

2. Raloxifene - In Detail

• Antagonist at ER in breast and uterine tissue
• Agonist at ER in bone - inhibits osteoclast-mediated bone resorption
• No estrogenic effect on endometrium (unlike tamoxifen)

• Postmenopausal osteoporosis - prevention and treatment
• Reduction of risk of ER-positive invasive breast cancer in postmenopausal women at high risk

• Hot flashes (less severe than tamoxifen)
• Thromboembolism risk (similar to tamoxifen)
• Does NOT increase endometrial cancer risk
• Less vaginal discharge compared to tamoxifen

b. First vs. Second Generation Antihistamines - Comparison & Indications

Classification

Comparison Table

Note on sedation among 2nd gen: Fexofenadine, Desloratadine, and Loratadine - least sedating. Cetirizine and Levocetirizine - partially sedating (but still far less than 1st gen).

Mechanism of Action (Both Generations)

• Act as competitive antagonists at H1 receptors
• Do NOT prevent histamine release or synthesis
• Block receptor-mediated response in target tissue
• More effective in preventing symptoms than reversing them once established
• First generation additionally: block muscarinic receptors (anticholinergic effects), alpha-adrenergic receptors (hypotension), serotonin receptors

Indications

• Allergic rhinitis
• Urticaria (hives) and angioedema
• Atopic dermatitis (as adjunct)
• Allergic conjunctivitis (topical forms: azelastine, olopatadine)
• Drug/food allergies
• Insect bite reactions

• Motion sickness - diphenhydramine, dimenhydrinate, meclizine, promethazine
• Nausea and vomiting - promethazine
• Pre-operative sedation - promethazine, hydroxyzine
• Sleep aid - diphenhydramine, doxylamine
• Cold preparations - chlorpheniramine (drying secretions via anticholinergic effect)
• Appetite stimulation - cyproheptadine

• Bronchial asthma as primary treatment (histamine is only one of many mediators; epinephrine is preferred for anaphylaxis)

c. Preanesthetic Medication - Why Required & Drugs Used

Definition

Why is Preanesthetic Medication Required? (Goals)

Drugs Used in Preanesthetic Medication

1. Benzodiazepines (most commonly used)

• Midazolam (IV/IM/oral) - short-acting, most popular
• Diazepam, Lorazepam
• Actions: Sedation, anxiolysis, amnesia, muscle relaxation, anticonvulsant
• Advantage: Reversible with flumazenil

2. Opioid Analgesics

• Morphine, Pethidine (Meperidine), Fentanyl
• Actions: Analgesia, sedation, euphoria, reduce anaesthetic requirement
• Disadvantage: Respiratory depression, nausea, vomiting, risk of histamine release (morphine)

3. Anticholinergics (Antisialagogues)

• Atropine (most commonly used), Glycopyrrolate, Scopolamine (Hyoscine)
• Actions:
  • Reduce salivary, bronchial, gastric secretions (dry field for intubation)
  • Prevent vagal bradycardia during laryngoscopy
  • Scopolamine also causes sedation and amnesia
• Atropine vs Glycopyrrolate: Glycopyrrolate preferred as it does NOT cross BBB (no CNS effects) and has longer duration

4. H2-Receptor Blockers / Antacids (for aspiration prophylaxis)

• Ranitidine, Famotidine, Omeprazole - reduce gastric acid production
• Sodium citrate - neutralize gastric acid
• Reduce risk of Mendelson's syndrome if aspiration occurs

5. Antiemetics

• Metoclopramide - prokinetic, raises gastric pH, reduces volume
• Ondansetron - 5-HT3 blocker; reduces PONV
• Promethazine - H1 blocker with antiemetic properties

6. Alpha-2 Agonists

• Clonidine, Dexmedetomidine
• Sedation, anxiolysis, analgesia, reduce intraoperative anaesthetic requirements
• Dexmedetomidine widely used for paediatric premedication

7. Antihistamines (H1 Blockers)

• Promethazine, Hydroxyzine
• Sedation + antiemetic + antihistamine cover

d. Shared Decision-Making (SDM)

Definition

"Shared decisions involve the doctor learning about the patient - their understanding, circumstances, and wishes - and the patient learning from the doctor about the nature of the treatment and the prognosis." (Scott-Brown's Otorhinolaryngology)

Why SDM Matters

• Improves patient satisfaction with consultation
• Leads to better quality of life outcomes
• Ensures informed consent is truly meaningful
• Respects patient autonomy and agency
• A "reasonable patient" standard now outweighs the "reasonable doctor" standard legally - patients have the right to know what they personally consider important, not just what a doctor thinks they need to know
• Reduces decisional conflict and increases adherence to treatment

Responsibilities of the DOCTOR in SDM

1. Provide complete, accurate, and understandable information about the diagnosis, treatment options, risks, benefits, and prognosis
2. Assess patient understanding - use "teach-back" method to verify comprehension
3. Explore patient values and preferences - what matters most to the individual patient
4. Present options without bias - avoid steering the patient toward a preferred option
5. Respect patient autonomy - acknowledge the patient's right to refuse or choose differently
6. Disclose a core set of information about all treatment options, including doing nothing
7. Use decision aids (pamphlets, visual tools) to help patients understand complex information
8. Provide adequate time for the patient to deliberate and ask questions
9. Document the process - record that SDM occurred and the patient's decision
10. Maintain confidentiality and trust - the therapeutic alliance depends on it

Responsibilities of the PATIENT in SDM

1. Actively participate in the consultation - ask questions, not remain passive
2. Share personal values, goals, and priorities that influence treatment choice
3. Disclose relevant information - lifestyle, other medications, social circumstances, cultural/religious beliefs
4. Seek to understand the information provided - ask for clarification when needed
5. Make an informed, autonomous decision - neither coerced nor simply deferring to the doctor
6. Communicate concerns and fears openly so the doctor can address them
7. Accept responsibility for the chosen decision once made with full information
8. Adhere to the agreed management plan and report back if things change
9. Recognize limits - if overwhelmed with information, communicate that to the doctor

Key Concept: Informed Consent vs. SDM

SDM is the broader concept; informed consent is a component of it. (Scott-Brown's Otorhinolaryngology)