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UNIT-VII — Medicinal Gases, Acidifiers, Antacids

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① Very Short Answer Type [2 Marks each]

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(i) What are Antacids? Give examples.

• Sodium Bicarbonate (NaHCO₃)
• Aluminium Hydroxide [Al(OH)₃]
• Magnesium Hydroxide [Mg(OH)₂]
• Calcium Carbonate (CaCO₃)
• Combination preparations: Gelusil, Maalox, Mylanta (Al(OH)₃ + Mg(OH)₂)

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(ii) What are Systemic and Non-Systemic Antacids?

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(iii) What is Achlorhydria? Give its treatment.

• Oral administration of dilute Hydrochloric Acid (Dilute HCl) — an acidifier
• Glutamic acid hydrochloride tablets
• Betaine hydrochloride
• Treatment of underlying cause (e.g., H. pylori eradication, pernicious anaemia management)

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(iv) Name the agents used as Acidifiers.

• Ammonium Chloride (NH₄Cl)
• Dilute Hydrochloric Acid

• Dilute Hydrochloric Acid
• Glutamic acid hydrochloride
• Betaine hydrochloride
• Ammonium chloride (also acidifies urine)

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(v) Name the Medicinal Gases with their use.

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(vi) Give the acid-neutralizing reaction of Sodium Bicarbonate.

• Reaction is rapid
• Produces CO₂ → causes belching/gastric distension
• Can cause metabolic alkalosis if absorbed in large amounts
• Contraindicated in hypertension, heart failure, renal insufficiency

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(vii) Define Buffers? Give examples of 2 official buffers.

1. Acetate Buffer — Acetic acid + Sodium acetate (pH 3.5–5.7)
2. Phosphate Buffer — Sodium dihydrogen phosphate + Disodium hydrogen phosphate (pH 5.8–8.0)

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(viii) What is Buffer Capacity and Iso-tonicity?

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(ix) Give the storage and labelling conditions of CO₂.

• Stored in steel cylinders painted grey (body: grey)
• Stored in cool, well-ventilated areas, away from heat and flames
• Cylinders kept upright and secured

• Cylinder colour: Grey (as per IP/BP standards)
• Labelled "CARBON DIOXIDE – MEDICINAL GAS"
• Should bear: name, purity, pressure, manufacturer details, batch number, expiry
• Cylinder valve outlet: specific non-interchangeable fittings (Pin Index Safety System — PISS) to prevent mix-up

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② Long Answer Type [10 Marks each]

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(i) Write the labelling and storage conditions for O₂.

Oxygen (O₂) — Official Requirements

• Manufactured by fractional distillation of liquefied air, or by electrolysis of water
• IP requirement: contains not less than 99% v/v of O₂

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1. Stored in seamless steel cylinders at high pressure (typically 13,700 kPa / ~137 atm)
2. Cylinder body: Black with White shoulder (IP/BS standard)
3. Stored in cool, dry, well-ventilated areas away from flammable materials, heat sources and open flames
4. Cylinders must be stored upright and secured against falling
5. Separate storage from flammable gases (e.g., N₂O, cyclopropane)
6. Liquefied oxygen stored in vacuum-insulated cryogenic vessels at −183°C
7. Cylinders must be periodically tested for pressure integrity

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• Hypoxia (respiratory failure, pneumonia, COPD)
• Carbon monoxide poisoning
• General anesthesia (carrier gas)
• Hyperbaric oxygen therapy (wound healing, decompression sickness)
• Neonatal resuscitation

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(ii) Define and classify antacids with examples. Add a note on combination antacid preparations.

Definition:

Base + HCl → Salt + H₂O e.g., Al(OH)₃ + 3HCl → AlCl₃ + 3H₂O

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Classification:

• Absorbed from GI tract → can cause metabolic alkalosis, sodium overload
• Sodium Bicarbonate (NaHCO₃) — fast-acting but not recommended for routine use
• NaHCO₃ + HCl → NaCl + H₂O + CO₂↑

1. Aluminium compounds:
   • Aluminium Hydroxide [Al(OH)₃]
   • Aluminium Hydroxide Gel (dried or magma)
   • Dihydroxyaluminium Sodium Carbonate
   • Effect: Causes constipation; slow-acting; also adsorbs pepsin
2. Magnesium compounds:
   • Magnesium Hydroxide [Mg(OH)₂] — "Milk of Magnesia"
   • Magnesium Carbonate, Magnesium Trisilicate
   • Effect: Causes diarrhea (osmotic); faster-acting than Al compounds
3. Calcium compounds:
   • Calcium Carbonate (CaCO₃)
   • CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑
   • Rapid; CO₂ causes belching; risk of milk-alkali syndrome
4. Bismuth compounds:
   • Bismuth Subcarbonate, Bismuth Subcitrate
   • Also have mucosal protective and antibacterial (anti-H. pylori) properties

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Ideal Properties of an Antacid:

1. High acid-neutralizing capacity
2. Non-absorbable (non-systemic)
3. Does not cause CO₂ generation (no belching)
4. No acid rebound
5. Palatable, affordable, readily available
6. Does not affect bowel habit (neither constipation nor diarrhea)
7. Does not interfere with drug absorption

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Combination Antacid Preparations (Note):

• Broader pH coverage
• Higher acid-neutralizing capacity
• Improved palatability

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(iii) What are Inhalants? Give the method of preparation, labelling, storage conditions, and medicinal use of Nitrous Oxide.

Inhalants:

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Nitrous Oxide (N₂O) — "Laughing Gas"

1. Manufactured by controlled thermal decomposition of ammonium nitrate:

   NH₄NO₃ →(~240–260°C)→ N₂O + 2H₂O

2. Crude gas is purified to remove NO, NO₂, NH₃, and higher oxides of nitrogen by washing through H₂SO₄, NaOH, and water scrubbers
3. Dried over CaCl₂ or silica gel
4. Compressed and liquefied into steel cylinders
5. IP standard: not less than 98% v/v N₂O

• Colourless, sweet-smelling gas
• Slightly heavier than air; non-flammable but supports combustion
• Critical temperature: 36.5°C (stored as liquid in cylinder)

• Stored as liquefied gas in blue cylinders (body: blue, shoulder: blue — IP)
• Stored away from heat and flammable substances
• Cylinder pressure ~50 bar at 15°C
• Upright in cool, ventilated store

• "NITROUS OXIDE – MEDICINAL GAS"
• Cylinder colour: Blue
• Purity not less than 98% v/v
• Volume, pressure, manufacturer, batch no., expiry date
• Pin Index positions: 3 and 5

1. General anesthesia: used as a carrier/adjuvant gas (with O₂ and volatile agents like isoflurane); weak anesthetic — MAC > 100%, so cannot produce anesthesia alone
2. Analgesia: "Entonox" (50% N₂O + 50% O₂) — used in labour pain, minor procedures, dental procedures
3. Procedural sedation

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(iv) What are Antacids? Give the ideal properties of antacids. Discuss preparation, assay, and use of Sodium Bicarbonate.

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Sodium Bicarbonate (NaHCO₃)

1. Solvay (Ammonia-Soda) Process (industrial):
   • Brine (NaCl solution) is saturated with NH₃, then CO₂ is passed through:

   NaCl + NH₃ + CO₂ + H₂O → NaHCO₃↓ + NH₄Cl

   • Precipitated NaHCO₃ is filtered, washed, and dried
2. Alternatively, by passing CO₂ through Na₂CO₃ solution

• White crystalline powder; odourless; slightly alkaline taste
• Freely soluble in water; insoluble in alcohol
• pH of 5% solution ~ 8.3

NaHCO₃ + HCl → NaCl + H₂O + CO₂↑

• Dissolve a known weight in water; titrate with 0.5 M HCl using methyl orange indicator
• Each mL of 0.5 M HCl = 42.00 mg NaHCO₃
• IP requires: not less than 99.0% and not more than 101.0% NaHCO₃ (dried basis)

1. Antacid — rapid relief of hyperacidity (not recommended for long-term use)
2. Systemic alkalinizer — treatment of metabolic acidosis
3. Urinary alkalinizer — relieves dysuria; used in UTIs
4. Mouthwash/gargle — mild antiseptic
5. Ingredient in combination antacid products and effervescent formulations

• Metabolic alkalosis (systemic absorption)
• Sodium overload (contraindicated in hypertension, CHF, renal failure)
• CO₂ generation → belching, gastric distension
• Acid rebound possible

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③ Short Answer Type [5 Marks each]

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(i) Give the method of preparation and use of Aluminium Hydroxide Gel.

Aluminium Hydroxide Gel [Al(OH)₃]

1. A solution of aluminium sulphate or aluminium chloride is prepared
2. Sodium hydroxide or ammonia solution is added to precipitate aluminium hydroxide:

   AlCl₃ + 3NaOH → Al(OH)₃↓ + 3NaCl Al₂(SO₄)₃ + 6NaOH → 2Al(OH)₃↓ + 3Na₂SO₄

3. The precipitate is washed thoroughly to remove chloride/sulphate ions
4. The gel is then filtered and concentrated to the desired consistency
5. IP specifies: Each mL contains approximately 4% w/v Al₂O₃ equivalent

• Aluminium Hydroxide Gel (liquid): Aqueous suspension for oral use
• Dried Aluminium Hydroxide Gel (tablets): For convenience; must be chewed

• Reacts with HCl: Al(OH)₃ + 3HCl → AlCl₃ + 3H₂O (no CO₂ generated)
• Also adsorbs pepsin, reducing proteolytic activity
• Raises gastric pH

1. Antacid — peptic ulcer, GERD, dyspepsia
2. Phosphate binder in chronic kidney disease (reduces hyperphosphatemia)
3. Mucosal protective agent

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(ii) State requirements for Ideal Antacids.

1. High acid-neutralizing capacity — reacts effectively with HCl
2. Non-systemic / Non-absorbable — does not cause metabolic alkalosis or systemic effects
3. No CO₂ generation — avoids belching and gastric distension
4. No acid rebound — does not stimulate secondary acid secretion
5. Palatable and pleasant — improves patient compliance
6. Rapid onset and prolonged action
7. Neither causes constipation nor diarrhea — does not disturb GI motility
8. Does not interfere with absorption of other drugs
9. Safe in renal impairment
10. Affordable and stable on storage

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(iii) Write the composition and uses of Talc and Kaolin.

Talc (Purified Talc)

• Composition: Hydrated magnesium silicate — Mg₃Si₄O₁₀(OH)₂
• Natural mineral; white or grayish-white, fine, impalpable, greasy powder
• Insoluble in acids and alkalis

1. Dusting powder — for skin (prevents friction/moisture)
2. Glidant and lubricant in tablet formulations
3. Filtering aid in pharmaceutical manufacturing
4. Used in cosmetics, talcum powder
5. As an antifungal/antiperspirant dusting agent
6. Pleurodesis — talc poudrage to treat recurrent pleural effusion

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Kaolin (Light Kaolin / Heavy Kaolin)

• Composition: Hydrated aluminium silicate — Al₂Si₂O₅(OH)₄ (kaolinite)
• White to pale cream fine powder; insoluble in water and dilute acids

1. Antidiarrheal — adsorbs bacteria, toxins, and fluid in the gut (Kaolin Mixture BP)
2. Adsorbent in gastroenteritis
3. Kaolin Poultice (BP) — used as warm poultice for pain/inflammation
4. Tablet filler/diluent in solid dosage forms
5. Used in cosmetics and as a clarifying agent

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(iv) Explain the physiological role of Copper and Chromium.

Copper (Cu):

• RDA: ~0.9 mg/day (adults)
• Storage: Liver, brain, kidney

1. Enzyme cofactor: Component of ceruloplasmin, cytochrome c oxidase, superoxide dismutase, lysyl oxidase
2. Iron metabolism: Ceruloplasmin oxidizes Fe²⁺ to Fe³⁺ for transferrin binding — essential for iron transport and haemoglobin synthesis
3. Antioxidant: Superoxide dismutase (Cu/Zn-SOD) neutralizes superoxide radicals
4. Connective tissue synthesis: Lysyl oxidase cross-links collagen and elastin
5. Melanin synthesis: Tyrosinase (copper-dependent) converts tyrosine → melanin
6. Neurological function: Dopamine β-hydroxylase converts dopamine → norepinephrine

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Chromium (Cr):

• RDA: ~25–35 µg/day (adults)
• Active form: Trivalent Cr(III)

1. Glucose metabolism (Insulin potentiation): Chromium forms a complex called chromodulin (also called Glucose Tolerance Factor, GTF) that enhances insulin receptor signalling → improves cellular glucose uptake
2. Lipid metabolism: Improves lipid profiles; reduces LDL and triglycerides; increases HDL
3. Protein synthesis: May enhance amino acid incorporation via insulin-mediated pathways
4. Nucleic acid metabolism: Maintains structural integrity of nuclear proteins and DNA

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Additional Questions (from right column of image)

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Sodium Bicarbonate — OTT agents and combination therapy

• Aspirin + Citric acid + NaHCO₃ → Alka Seltzer (effervescent antacid/analgesic)
• Alginate + NaHCO₃ → Gaviscon — NaHCO₃ releases CO₂ which is trapped in alginate raft, forming a physical barrier floating on gastric contents

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Enlist different antacids; write the preparation and use of Aluminium Hydroxide Gel

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UNIT-VII — Cathartics, Electrolyte Replenishers

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① Very Short Answer Type [2 Marks each]

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(i) Write different types of Cathartics.

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(ii) Define Saline Cathartics with examples.

• Magnesium Sulphate (Epsom salt) — most commonly used
• Magnesium Hydroxide (Milk of Magnesia)
• Magnesium Citrate
• Sodium Phosphate
• Sodium Sulphate (Glauber's salt)

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(iii) Define Extra and Intracellular Electrolytes with examples.

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(iv) What is Electrolyte Combination Therapy?

• ORS (Oral Rehydration Solution): Na⁺ + K⁺ + Cl⁻ + HCO₃⁻/citrate + glucose
• Ringer's Lactate (Hartmann's solution): Na⁺ + K⁺ + Ca²⁺ + Cl⁻ + lactate
• Normal Saline: NaCl 0.9%
• Darrow's solution: Na⁺ + K⁺ + Cl⁻ + lactate (used in severe dehydration with hyponatraemia)

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(v) What is the full form of ORS?

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(vi) What are OTT agents?

• Magnesium hydroxide (Milk of Magnesia) — OTC laxative/antacid
• Calcium carbonate (Tums) — OTC antacid
• PEG 3350 (Miralax) — OTC osmotic laxative
• Sodium bicarbonate (Alka Seltzer) — OTC antacid/effervescent

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(vii) What are the uses of Aluminium Hydroxide Gel?

1. Antacid — treatment of peptic ulcer, GERD, gastritis, hyperacidity
2. Phosphate binder — in chronic kidney disease (CKD) to reduce hyperphosphataemia
3. Adsorbs pepsin — reduces proteolytic mucosal damage
4. Mucosal protective agent — forms a gel coat over ulcer base
5. Adjuvant in vaccines — aluminium hydroxide gel used as an immunological adjuvant (alum)
6. Treatment of fluoride poisoning — binds fluoride ions in GI tract

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(viii) What are major physiological ions?

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(ix) Name the natural buffer systems in the human body.

1. Bicarbonate–Carbonic Acid Buffer (most important ECF buffer): HCO₃⁻/H₂CO₃ — pKₐ 6.1; effective for metabolic disturbances
2. Phosphate Buffer: HPO₄²⁻/H₂PO₄⁻ — important in urine and intracellular fluid
3. Protein Buffer (intracellular): Plasma proteins (albumin), intracellular proteins — major ICF buffer
4. Haemoglobin Buffer: Most effective buffer against both respiratory (CO₂) and metabolic acids; works via imidazole groups of histidine
5. Ammonia Buffer System (renal): NH₃ + H⁺ → NH₄⁺ — important in urine acidification

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(x) What is the role of Sodium, Calcium, Chloride, and Bicarbonate ions?

• Maintains ECF osmolality and volume
• Essential for nerve impulse transmission (action potential)
• Drives Na⁺/K⁺-ATPase pump
• Controls water distribution between compartments

• Bone and teeth mineralization (99% in skeleton)
• Muscle contraction (troponin C binding)
• Neurotransmitter release
• Blood coagulation (Factor IV)
• Second messenger in cell signalling
• Cardiac conduction

• Principal anion of ECF; maintains electroneutrality
• Component of gastric HCl (digestion)
• Chloride shift in RBCs during CO₂ transport
• Regulates osmotic pressure alongside Na⁺

• Primary buffer of blood (normal: 22–28 mEq/L)
• Transports CO₂ from tissues to lungs (CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻)
• Regulated by kidneys to maintain pH 7.35–7.45
• Alkalinizes urine

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② Long Answer Type [10 Marks each]

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(i) Explain the mechanism of maintenance of physiological acid-base balance. Write a note on the biochemical and biological role of Na⁺ and HCO₃⁻ ions.

Physiological Acid-Base Balance

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1. Bicarbonate Buffer (most important ECF buffer):

   CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻ (catalysed by carbonic anhydrase)

   • pH = pKₐ + log([HCO₃⁻] / [H₂CO₃]) = 6.1 + log(20/1) = 7.40
   • Normal ratio HCO₃⁻ : H₂CO₃ = 20:1 (must be maintained)
   • Effective against metabolic disturbances; not effective for respiratory disturbances (cannot buffer H₂CO₃)
2. Haemoglobin Buffer:
   • Buffers both CO₂ (respiratory) and noncarbonic (metabolic) acids
   • Deoxyhaemoglobin is a better buffer than oxyhaemoglobin
   • Imidazole groups of histidine residues accept H⁺
3. Plasma Protein Buffer: albumin and globulins have free -NH₂ and -COOH groups
4. Phosphate Buffer (intracellular/urine):

   HPO₄²⁻ + H⁺ ↔ H₂PO₄⁻ (pKₐ 6.8 — ideal for intracellular pH ~7.0)

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• Medullary chemoreceptors detect changes in PaCO₂ and pH
• Acidosis: ↑ ventilation → blows off more CO₂ → raises pH
• Alkalosis: ↓ ventilation → CO₂ retained → lowers pH
• Relationship: PaCO₂ rises ~0.25–1 mmHg for each 1 mEq/L rise in HCO₃⁻

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1. Reabsorption of HCO₃⁻ — primarily in proximal tubule; enhanced in acidosis
2. Excretion of titratable acids — H₂PO₄⁻ in distal tubule
3. Ammonia production (ammoniagenesis):

   Glutamine → NH₃ + glutamate (in tubular cells) NH₃ + H⁺ → NH₄⁺ (secreted into urine)

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(ii) List major intra- and extracellular electrolytes. Explain the preparation and uses of Dextrose and Sodium Chloride Injection.

Major Electrolytes:

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Sodium Chloride Injection (Normal Saline)

1. Dissolve 9 g NaCl in sufficient Water for Injection (WFI)
2. Make up volume to 1000 mL
3. Adjust pH to 4.5–7.0 (IP)
4. Filter through 0.22 µm membrane
5. Fill into sealed glass ampoules or infusion bags
6. Sterilize by autoclaving (121°C, 15 min) or by aseptic filtration

• 0.45% NaCl (hypotonic — "half-normal")
• 3% NaCl (hypertonic — for severe hyponatraemia)

1. ECF volume replacement in dehydration, shock, haemorrhage
2. Hyponatraemia (0.9% or 3% NaCl)
3. Vehicle for IV drug administration
4. Wound irrigation and eye drops (0.9%)
5. Nasal saline spray (congestion)
6. Emergency resuscitation

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Dextrose Injection (Glucose Injection)

• 5% w/v — isotonic (~278 mOsm/L)
• 10%, 25%, 50% — hypertonic

1. Dissolve anhydrous dextrose in WFI
2. Adjust pH to 3.5–6.5 (IP) — slightly acidic to prevent caramelisation during sterilisation
3. Filter and fill into sealed containers
4. Sterilize by autoclaving (121°C, 15 min)

1. Caloric (energy) source — 5% dextrose provides 200 kcal/L; used in starvation, pre/post-operatively
2. Hypoglycaemia — 25–50% dextrose IV (emergency)
3. Vehicle for IV drugs and electrolytes
4. Hyperkalaemia — glucose + insulin drives K⁺ into cells
5. Cerebral oedema — 20% mannitol (osmotic); hypertonic dextrose (adjunct)
6. Hepatic failure — provides energy while sparing protein catabolism

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(iii) Name the major physiological ions and write their role. Add a note on physiological acid-base balance.

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(iv) Define Cathartics. Give the preparation and assay of Magnesium Sulphate.

Definition:

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Magnesium Sulphate (Epsom Salt)

• Colourless, efflorescent crystals or white granular powder
• Bitter saline taste
• Freely soluble in water; practically insoluble in alcohol
• Loses water of crystallisation on heating

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MgCO₃ + H₂SO₄ → MgSO₄ + H₂O + CO₂

• Solution evaporated and crystallised to obtain MgSO₄·7H₂O

• Dolomite (CaMg(CO₃)₂) reacted with H₂SO₄
• CaSO₄ precipitates out; MgSO₄ remains in solution
• Concentrated and crystallised

Mg(OH)₂ + H₂SO₄ → MgSO₄ + 2H₂O

• Crystallised as heptahydrate by cooling

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1. Dissolve accurately weighed sample (~0.2 g) in water
2. Add ammonia buffer (pH 10)
3. Add indicator: Eriochrome Black T (EBT) (solution turns wine-red)
4. Titrate with 0.05 M disodium EDTA until colour changes from wine-red to pure blue

MgSO₄ + EDTA (Na₂H₂Y) → [Mg-EDTA]²⁻ complex + 2H⁺

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③ Short Answer Type [5 Marks each]

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① Write a note on Physiological Acid-Base Balance.

pH = 6.1 + log( [HCO₃⁻] / 0.0307 × PaCO₂ )

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② Describe the important functions of Bicarbonate and Sodium ions in the body.

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③ Write a note on Electrolytes used in Replacement Therapy.

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④ Write the composition and use of ORS.

WHO-ORS (Revised Low-Osmolarity, 2003):

1. Treatment of acute dehydrating diarrhoea (cholera, gastroenteritis)
2. Vomiting and dehydration in children
3. Heat exhaustion / exercise-induced electrolyte loss
4. Post-surgical fluid replacement (mild)
5. Prevention and treatment of dehydration in resource-limited settings

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⑤ Write a note on the Buffer Systems of the Body.

1. Bicarbonate buffer — ECF, plasma (pKₐ 6.1)
2. Haemoglobin buffer — RBCs (best for both respiratory and metabolic)
3. Plasma protein buffer — albumin, globulins
4. Phosphate buffer — ICF and urine (pKₐ 6.8)

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⑥ Give the preparation and assay of Magnesium Sulphate.

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Additional 2-Mark Questions (Right Column)

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⑤ What are Saline Cathartics? What is their mechanism of action?

• Osmotic retention: Poorly absorbed Mg²⁺/SO₄²⁻ ions retain water in intestinal lumen by osmosis
• CCK stimulation: Mg²⁺ stimulates release of cholecystokinin → fluid and electrolyte secretion + enhanced intestinal motility
• Direct mucosal effect: May stimulate release of inflammatory mediators
• Result: Watery evacuation within 0.5–6 hours

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⑥ Give the method of preparation, assay, medicinal use of Magnesium Sulphate with its chemical formula and synonym.

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