Lab chemical incomp

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Created by
Nicole Ablaza

Cards (53)

  • UNIT 3: CHEMICAL INCOMPATIBILITIES
  • Chemical Incompatibilities
    • Immediate Incompatibility
    • Delayed Incompatibility
    • Generalize Chemical Incompatibilities
  • Chemical Reactions
    1. Oxidation
    2. Hydrolytic Changes
    3. Evolution of Gas
    4. Displacement
    5. Complexation
    6. Racemization
    7. Epimerization
    8. Formation of Sparing Soluble Salts
    9. Reduction
    10. Color Changes
    11. Explosive Combinations
    12. Cementation
    13. Separation of Immiscible Liquids
    14. Gelatinization
    15. Development of Heat or Cold
    16. Invisible Changes
    17. Development of Poisonous Substances
    18. Other type of Chemical Change
  • Chemical Incompatibilities occur as a result of chemical interaction among the ingredients of a prescription, where the original composition is altered
  • Compounds Considered Soluble
    • All acetates
    • All nitrates
    • Sulfates, except Ba, Sr, Pb, and Ag
    • All sodium salts
    • Potassium salts except barbiturates
    • Chlorides except silver and mercurous
  • Compounds Considered Insoluble
    • Carbonates, except those of the alkalis
    • Phosphates, except those of the alkalis
  • Immediate Incompatibility occurs instantaneously upon compounding and is readily apparent due to effervescence, precipitation, or color changes
  • Delayed Incompatibility occurs on a slow rate without appreciable visible change or immediate physical evidence of change, which may or may not result in the loss of therapeutic activity
  • Remedies for Incompatibilities include using labels like "Store in a Refrigerator" or "Shake well" to address storage and stability issues
  • Ingredients with chemically similar active groups are usually compatible, while those with different active groups may sometimes react
  • TO GENERALIZE CHEMICAL INCOMPATIBILITIES
  • Factors enhancing chemical reactions
    • Adverse Temperatures
    • Light
    • Humidity
    • Oxygen
    • Carbon dioxide
    • Over dilution
    • Excessive Storage
    • Incorrect pH Adjustment
    • Presence of Catalysts
  • Chemical reactions
    Enhanced by factors such as adverse temperatures, light, humidity, oxygen, carbon dioxide, over dilution, excessive storage, incorrect pH adjustment, and presence of catalysts
  • Oxidation

    • Second most common degradation method
    • Drugs susceptible to oxidation include Catecholamines, Phenolics, Phenothiazines, Olefins, Steroids, Tricyclics, Thiols, and Miscellaneous drugs
    • Oxidation induces compounds to free radicals
    • Compounds that undergo auto-oxidation include oils, fats, phenolic substances, aldehydes, and vitamins
    • Remedies for oxidation include protecting from oxygen, using tight containers, limiting storage time, and using metal-chelating agents and antioxidants
  • DRUG USUAL BUD: Paracetamol - 24 hours, Paper Tabs - 1 month (Solids), Semi-solid preparations - 14 days, Antibiotics - 7-14 days
  • Remedies for oxidation
    • Protect from oxygen by using tight containers and limiting storage time through conservative BUDs
    • Add a metal-chelating agent like edetate disodium
    • Add an antioxidant
    • Control storage temperature
    • Control pH because alkaline pH increases oxidation
    • Separate dr
  • Academic Year
    2023-2024
  • Drugs susceptible to hydrolysis
    • Esters (e.g. Procaine, Tetracaine, Aspirin compounds with lactone rings)
    • Amides (e.g. Penicillins)
    • Imides (e.g. Barbiturates)
    • Thiolesters
  • Hydrolytic changes
    1. Ionic hydrolysis: Ionized species + H+ or OH- of H2O → Unionized insoluble product
    2. Molecular hydrolysis: Slower than ionic, reduced therapeutic activity
  • Representative drugs for evolution of gas (CO2)
    • Sodium bicarbonate and carbonate buffers
    • Ortho- and para-substituted benzoic acids, like p-aminosalicylic acid
  • Cisplatin is displaced by water

    Chloride is displaced by water which will become inactive
  • For solids, control exposure to moisture by using tight containers and desiccants
  • Control the pH of aqueous formulations
  • Check effect of general acids or bases and drug concentration
  • Control storage temperature
  • Do not combine drug products that generate acid pH with sodium bicarbonate or drug products that contain carbonate buffers
  • Vulnerable solid dosage forms must be stored in tight containers
  • DISPLACEMENT
    1. Cisplatin is the best-known example
    2. Maintain 0.2% NaCl solution for cisplatin
    3. Use stainless-steel needles for drawing and administering the drug
    4. Once the cisplatin is administered, the chloride is displaced by water which will become inactive. Hence, apply the necessary remedies such as maintaining 0.2% NaCl solution and using stainless-steel needles
  • COMPLEXATION
    1. Representative drugs: Tetracycline by multivalent ions like calcium, magnesium, iron, and aluminum
    2. Remedy: Keep the drug from offending ions. Patients should be counseled to avoid taking the drug with food or drugs containing multivalent ions. Milk and iron supplements must be avoided when taking tetracycline as it can lead to complexation
    3. Representative drugs: Aminophylline is a complex with a 2:1 ratio of theophylline and ethylenediamine. Theophylline may precipitate out of solution. Complexation is a reversible reaction
    4. Remedies: Addition of excess ethylenediamine to keep theophylline in the complex. Maintain pH of 8.6 to 9 using ethylenediamine
  • RACEMIZATION
    1. A mixture of equal parts of enantiomers is called a racemate, and the conversion of one enantiomer to a racemate is known as racemization. Enantiomers are isomers that mirror each other. The conversion of an isomer to racemate is racemization
    2. Examples: epinephrine, mepivacaine and bupivacaine, amphetamine and dextroamphetamine, albuterol and levalbuterol, omeprazole and esomeprazole
  • EPIMERIZATION
    1. A pair of diastereomers that differ only in the configuration about one carbon atom are called epimers. Diastereomers are not mirror images of each other. They have the same functional groups and they show chemical properties but have different rates of reactions
    2. Examples: Tetracycline epimerized to epitetracycline (with little antibacterial activity). Another common example is pilocarpine which epimerizes leading to reduced pharmacological activity
    3. Remedy: Formulation of suspension. Control of pH with buffers
  • FORMATION OF SPARINGLY SOLUBLE SALTS
    When a drug is dissolved in a solvent and another drug is added, it will form a sparingly soluble salt
  • DRUGS WITH UNUSUAL COUNTER IONS
    Organic salts with a special or unusual counter ion, such as mesylate, lactate, succinate should be added with caution to another salt
  • ALKALOIDAL PRECIPITANTS
    1. Precipitation of alkaloids caused by citrate salts, tannins, iodide and picric acid
    2. Remedy: Addition of alcohol or glycerin to prevent precipitation
  • REDUCTION
    Less common
  • Anic salts with special or unusual counter ions

    • mesylate
    • lactate
    • succinate
  • Anic salts with special or unusual counter ions should be added with caution to another salt
  • Alkaloidal precipitants
    • citrate salts
    • tannins
    • iodide
    • picric acid
  • Remedy
    Addition of alcohol or glycerin to prevent precipitation
  • Reduction

    Less common in Rxs although silver, mercury, and gold salts may be reduced by light to the metallic form