Pharmaceutical Chemistry · Short notes

Inorganic Pharmaceutical Chemistry: Short Notes & Cheat Sheet

Antacids, electrolytes and ORS, antimicrobial inorganics, dental agents, haematinics, radiopharmaceuticals and limit tests.

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Short notes

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Limit tests at a glance

Each limit test compares the sample with a standard under identical conditions; it does not measure the exact amount.

Antacids and GI agents

Aluminium hydroxide causes constipation and binds phosphate. Magnesium hydroxide and magnesium trisilicate cause diarrhoea, so they are often combined.
Sodium bicarbonate is a systemic antacid: it is absorbed and can cause metabolic alkalosis and sodium load.
Calcium carbonate can cause acid rebound, constipation and, with milk, the milk–alkali syndrome.
Magnesium sulfate (Epsom salt) is an osmotic laxative, and given IV it prevents eclamptic seizures. Sodium sulfate is Glauber's salt.
Barium sulfate is used as an X-ray contrast agent because it is insoluble. Soluble barium salts such as the carbonate are poisonous.

Electrolytes and fluids

Normal saline (0.9% NaCl) contains 154 mmol/L each of sodium and chloride.
WHO low-osmolarity ORS (245 mOsm/L): sodium 75, chloride 65, glucose 75, potassium 20 and citrate 10 mmol/L.
Ringer's lactate (Hartmann's) contains sodium, potassium, calcium, chloride and lactate; the lactate is converted to bicarbonate in the liver.
Potassium chloride must never be given as an IV bolus; it is diluted and infused slowly.
Calcium gluconate treats hypocalcaemia and protects the heart in hyperkalaemia.

Topical and antimicrobial agents

Hydrogen peroxide 3% ('10 volume') releases oxygen and cleans wounds by effervescence.
Potassium permanganate is an oxidising antiseptic used as a dilute (about 1 in 10,000) solution for weeping skin.
Iodine: Lugol's solution is 5% iodine with 10% potassium iodide (KI makes iodine soluble). Povidone-iodine is an iodophor that releases iodine slowly.
Zinc oxide is an astringent and protective; calamine is zinc oxide with a little ferric oxide for colour.
Silver nitrate is caustic and antiseptic. Boric acid is a weak antiseptic that is toxic to infants.
Sodium fluoride prevents caries but excess causes fluorosis. Strontium chloride and potassium nitrate reduce dentine sensitivity.

Radiopharmaceuticals and limit tests

Technetium-99m is the most used diagnostic isotope: a pure gamma emitter with a 6-hour half-life.
Iodine-131 treats hyperthyroidism and thyroid cancer. Cobalt-60 is used in radiotherapy and for sterilising medical devices by gamma radiation.
Limit tests control harmful impurities by comparing the sample with a standard.

Cheat sheet

High-yield facts in one place. Cover the right-hand column and test yourself.

Limit tests

Impurity	Reagent · result
Chloride	Silver nitrate + HNO₃ · opalescence
Sulfate	Barium chloride + HCl · turbidity
Iron	Thioglycolic acid + citric acid + NH₃ · purple
Heavy metals	Thioacetamide / H₂S · brown (vs lead standard)
Arsenic	Gutzeit: Zn + HCl → arsine · yellow–brown stain on HgCl₂ paper
Lead	Dithizone · red colour

Iron salts (elemental iron)

Salt	Iron content
Ferrous fumarate	≈ 33%
Ferrous sulfate (dried)	≈ 30%
Ferrous sulfate (hydrated)	≈ 20%
Ferrous gluconate	≈ 12%

Quick identities

Name	Compound
Epsom salt	Magnesium sulfate
Glauber's salt	Sodium sulfate
Milk of magnesia	Magnesium hydroxide
Calamine	Zinc oxide + ferric oxide
Plaster of Paris	Calcium sulfate hemihydrate
Lunar caustic	Silver nitrate

Memory aids

Aluminium = Anchors, Magnesium = Moves: Aluminium antacids constipate; magnesium antacids loosen the bowel.
Tc-99m: 6 hours, pure gamma: Ideal for imaging: short half-life and no particle radiation.

Exam traps

Barium sulfate is safe because it is insoluble; barium carbonate dissolves in stomach acid and is toxic.
Sodium bicarbonate, not calcium carbonate, is the classic systemic antacid causing alkalosis.
In the Gutzeit test the arsenic is converted to arsine gas, which stains mercuric chloride paper.
Lugol's solution contains both iodine and potassium iodide; the iodide keeps the iodine in solution.

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