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Find these notes by Typing lines as given below in Search… Expectorants Expectorants are drugs used to help in the removal of sputum from the respiratory tract, or simply put, they are used in the treatment of cough. ● Cough is a protective physiological reflex that helps to clear the respiratory tract. ● Cough can be further divided into two types:
- Dry Cough (No sputum discharge)
- Productive Cough (Sputum discharge)
Classification of Expectorants
Expectorants act by two mechanisms: ● Increasing fluidity (or reducing viscosity) of sputum. ● Increasing the volume of sputum. Based on these mechanisms, expectorants can be classified into two categories:
- Sedative Expectorants
- Stimulant Expectorants
1. Sedative Expectorants
● These are stomach irritant expectorants. ● They produce their effect by increasing gastric reflexes. ● They cause sedation (sleep) in patients. ● Therefore, they act by increasing the volume of sputum.
2. Stimulant Expectorants
● They act by stimulating the secretory cells of the respiratory tract directly or indirectly. ● These drugs stimulate secretion, leading to more fluid production in the respiratory tract, which dilutes the sputum and makes it easier to discharge through coughing. ● Hence, these drugs act by increasing the fluidity of sputum (or reducing its viscosity). Potassium Iodide ● Molecular Formula: KI ● Molecular Weight: 166 g/mol ● Synonyms: Kalium Iodatum
Method of Preparation
When hydrogen iodide is treated with potassium bicarbonate, it results in the formation of potassium iodide. KHCO3+HI → KI+H2O+CO
Properties
- The excess of silver nitrate is titrated with 0.1 N ammonium thiocyanate using 2 mL of ferric ammonium sulfate as an indicator. NH4Cl+AgNO3 → NH4NO3+AgCl Each mL of 0.1N AgNO₃ ≈ 0.005349 g of NH₄Cl Note: The above assay method was previously used. Nowadays, ammonium chloride is assayed using Acid-Base Titration.
Emetics
● Definition: Emetics are drugs that cause vomiting (emesis).
● Mechanism:
○ Vomiting is a forceful expulsion of the stomach's contents via the mouth or sometimes through the nose. ○ Emetics plays a valuable role in the treatment of poisoning. ○ They are also used in the treatment of drug overdose or adverse drug effects. ○ In low doses, emetics are sometimes added to cough preparations to stimulate the flow of respiratory tract secretions. ○ Vomiting is an involuntary process.
Mechanism of Action of Emetics:
● Emetics generally act through two mechanisms:
- Direct Action: By stimulating the chemoreceptor trigger zone located in the medulla oblongata in the brain.
- Indirect Action: By causing irritation in the gastrointestinal tract. Copper Sulphate ● Molecular Formula: CuSO₄·5H₂O ● Molecular Weight: 159.6 g/mol ● Synonyms: Blue Vitriol
Method of Preparation:
● Copper sulphate is prepared by dissolving cupric carbonate in dilute H₂SO₄ CuCO₃ + H₂SO₄ → CuSO₄ + H₂O + CO₂
Properties:
● Appears as blue crystalline granules or in powdered form. ● It is odorless. ● It is soluble in water. ● It is insoluble in alcohol.
Assay:
● The assay of copper sulphate is performed by Redox Titration. ● An accurately weighed quantity of CuSO₄ is dissolved in water. ● To this solution, excess potassium iodide is added, followed by acetic acid. ● The liberated iodine is titrated with standard sodium thiosulphate solution using starch solution as an indicator.
● Used in effervescent powders.
Haematinics
● Definition: Haematinics are substances required for the formation of blood and are mainly used in the treatment of anemias. ● Function: ○ These drugs increase the number of red blood cells and the amount of hemoglobin when they are below normal levels. ○ Anemia occurs when the balance between the production and destruction of red blood cells gets disturbed.
Anemia:
● Definition: Anaemia is a state of the body where the concentration of hemoglobin is reduced in the blood. ● Causes:
- Excessive blood loss
- Unhealthy RBC formation
- Increased destruction of RBCs Types of Anaemia: ● Iron Deficiency Anaemia ● Aplastic Anaemia ● Haemolytic Anaemia ● Sickle Cell Anaemia ● Pernicious Anaemia
Ferrous Sulphate
● Molecular Formula: FeSO₄·7H₂O ● Molecular Weight: 278 g/mol ● Synonyms: Green Vitriol
Method of Preparation:
● When iron is treated with dilute H₂SO₄, iron dissolves and forms ferrous sulphate, releasing hydrogen gas: Fe + H₂SO₄ → FeSO₄ + H₂ Properties: ● Occurs as transparent green crystals or pale bluish-green crystalline powder. ● It is odorless. ● It has a metallic taste. ● It is soluble in water. ● It is insoluble in alcohol. Assay: ● The assay of ferrous sulphate is performed using Redox Titration. ● Add about 0.76 g of FeSO₄ in 100 ml of water. ● Add 0.1 ml of 3-drop H₂SO₄ as an indicator. ● Titrate with 0.1 N KMnO₄ standard solution until the purple color disappears. Uses: ● Used as haematinics.
● Dilated pupils ● Decreased heart rate Cyanide Poisoning ● Occurrence: ○ Cyanide poisoning can occur by accidentally taking cyanide poison. ○ Cyanide poisoning can also occur intentionally as a means to commit suicide. ● Mechanism: ○ Cytochrome Oxidase is an enzyme responsible for electron transfer reactions necessary for cellular respiration. ○ In cyanide poisoning, cyanide binds with the ferric ion of cytochrome oxidase. ○ This binding leads to the stoppage of electron transfer reactions, ultimately inhibiting cellular respiration. ○ If cyanide poisoning is not treated immediately, it can be very harmful and potentially fatal. ● Treatment: ○ Sodium nitrite and sodium thiosulphate injections are administered, one after the other, as antidotes for cyanide poisoning. Antidotes ● Definition: ○ Antidotes are substances that specifically react with ingested poison to neutralize its effects.
○ They are used to neutralize the effects of poison in the body. ● Classification: ○ Antidotes are classified based on their mechanism into three categories:
- Physiological Antidotes
- Chemical Antidotes
- Mechanical Antidotes Physiological Antidotes: ● Also called Antagonists. ● They produce effects opposite to that of the poison. ● Example: Sodium nitrite. Chemical Antidotes: ● They act by combining with the poison, changing its chemical structure, or converting it into an inactive or harmless compound. ● Example: Sodium thiosulphate. Mechanical Antidotes: ● They act by preventing the absorption of poison into the body. ● Example: Activated charcoal. Sodium Thiosulphate ● Molecular Formula: Na₂S₂O₃·5H₂O ● Molecular Weight: 248.2 g/mol
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