15. INCOMPATIBILITIES

Incompatibilities

Introduction:

Incompatibility is defined as the mixing of two or more antagonistic substances resulting in undesirable products that affect safety, efficacy, and appearance of pharmaceutical preparations.

Classification and Remedies:

Incompatibilities are classified into three types:

1. Physical Incompatibilities: Visible physical changes like immiscibility, insolubility, liquefaction. Corrected by pharmaceutical techniques such as emulsification or use of suspending agents.
2. Chemical Incompatibilities: Caused by reactions like pH changes, redox, hydrolysis leading to precipitation, color changes, or decomposition. Managed by careful separation or added stabilizers.
3. Therapeutic Incompatibilities: Undesired pharmacological effects due to drug interactions or improper dosages resulting in antagonism or altered therapeutic effect. Avoided by verifying prescriptions.

Physical Incompatibilities:

• Immiscibility: Oil and water not mixing; remedied by emulsifying agents.
• Insolubility: Indiffusible solids precipitate; suspending agents like tragacanth used.
• Liquefaction: Eutectic mixtures liquefy below room temperature; managed by separate dosing or adsorbents like kaolin or starch.

Chemical Incompatibilities:

• Examples include alkaloidal salts with alkaline substances, salicylates forming precipitates with quinine or ferric salts, evolution of CO2 from acid and carbonate mixtures, or explosive mixtures like potassium chlorate and tannic acid.
• Remedies involve separate dissolution, use of mucilage suspensions, shifting vehicles, or dividing doses in separate containers with instructions.

Therapeutic Incompatibilities:

• Errors in dosage or form, prescribing contraindicated drugs, synergistic or antagonistic drug combinations, drug interactions, or incorrect directions can cause therapeutic incompatibility.
• Examples include overdosing atropine, confusion between similarly named drugs, antagonistic drug pairs like acetophenetidin and caffeine, and drug-food interactions such as tetracycline with milk.
• Pharmacists must carefully evaluate prescriptions to avoid these.

Effective management of incompatibilities is critical for patient safety and therapeutic success. Knowledge of these incompatibilities is essential for pharmacists during dispensing and counseling.

Detailed Notes:

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