Tema 4: Pureza de drogas y medicamentos

Understanding Drug Purity and Quality Control

The Importance of Identifying Active Ingredients

• The process begins with identifying or confirming the active ingredient or excipient in a pharmaceutical product, which is crucial for quality control.

• Once impurities are quantified in a sample, if they exceed acceptable levels, the quality control process cannot proceed, leading to potential disposal of the pharmaceutical product.

Relative Purity Standards

• Pure drugs are expected to have relative purity; achieving 100% purity is unrealistic and not mandated by pharmacopoeias.

• Higher purity often results in increased production costs. Thus, organizations like WHO advocate for relative purity standards rather than absolute ones.

Purification Processes and Their Implications

• Raw materials undergo analysis for purity before production; low-purity materials require purification processes that lead to material loss.

• For example, starting with 1000 kg at 80% purity means only 800 kg meets production standards after purification, resulting in significant losses.

Cost-Benefit Analysis of Purity

• The purification process incurs both material loss and increased costs; as raw material becomes purer, its price escalates significantly.

• International guidelines suggest that absolute purity (e.g., 99.99%) is impractical due to cost implications for mass production.

Examples Illustrating Purity Levels

• Common salt serves as an example: industrial-grade salt has about 95% purity costing approximately two bolivianos per kilo.

• Further purification yields kitchen salt (99% pure), costing around five bolivianos per kilo; therapeutic-grade sodium chloride can reach prices up to 120 bolivianos per kilo due to higher purification levels.

By understanding these concepts surrounding drug purity and quality control processes, one can appreciate the balance between maintaining effective medication standards while managing economic feasibility.

Understanding Drug Purity and Impurities in Pharmaceuticals

The Concept of Useful Drugs

• Johnson defines a "useful drug" as one that, at 99% purity, is economically viable for producing medication batches. In contrast, a substance at 99.9% purity becomes an academic curiosity due to its high cost.

Importance of Relative Purity

• The discussion highlights the significance of relative purity in pharmaceuticals. A slight increase in purity from 99% to 99.9% can drastically raise production costs, making medications unaffordable for many.

Types of Impurities and Their Risks

• Pharmaceutical manufacturers specify required purities (e.g., ciprofloxacin at 96%) to avoid costly purification processes before production.

• Impurities can be toxic or potent; toxic impurities like arsenic and lead pose serious health risks even in small amounts.

Toxic Impurities: Examples and Consequences

• Arsenic accumulates in the body and can cause death at levels as low as 8-10 parts per million. Lead contamination often arises from metal containers used during raw material transport.

• Chronic lead poisoning, known as saturnism, exemplifies the dangers posed by toxic impurities found in pharmaceutical materials.

Historical Context of Toxic Impurities

• Fenacetin was previously used but contained parafenetidina as an impurity, leading to adverse reactions among users due to its toxicity.

Potent Impurities: Effects on Health

• Potent impurities do not necessarily cause toxicity but can trigger adverse reactions; pyrogens are common examples found in injectable drugs that may originate from environmental contaminants.

• Quality control measures must ensure environments are strategically located away from human traffic and equipped with filters to prevent pyrogen contamination.

Modern Detection Methods for Pyrogens

• Advances have replaced older methods (like visual inspection or animal testing) with modern technology for detecting pyrogens effectively without using live subjects.

Additional Types of Impurities: Alterations Caused by Environmental Factors

• Humidity is a significant factor causing degradation in pharmaceuticals; it affects effervescence in products like effervescent tablets over time when exposed to moisture.

• Metals acting as catalysts during production also contribute to alterations within pharmaceutical compounds, necessitating stringent quality controls during manufacturing processes.

Impurities in Pharmaceutical Production

Types of Impurities

• The discussion begins with the identification of impurities in pharmaceuticals, emphasizing that machinery and equipment used are often made from metal alloys, which can introduce impurities.

• Impurities can lead to incompatibilities, categorized as either pharmacotechnical or therapeutic. A common example is the use of poorly distilled water, which can affect drug solubility.

Sources of Contamination

• Poorly distilled water may contain chlorides and carbonates that hinder proper mixing when reconstituting medications, necessitating additional agitation.

• Glass containers must be made from neutral silicates to prevent solubility issues; low-quality glass can introduce harmful impurities into medications.

Quality Control Measures

• Raw materials arrive at pharmaceutical facilities with inherent impurity levels. Quality control labs analyze these materials and issue certificates confirming their suitability for production.

• The purity and potency of active ingredients are crucial; only pure substances yield effective medications.

Auxiliary Substances and Manufacturing Processes

• Previously considered innocuous, auxiliary substances (like colorants or preservatives) are now recognized as potential sources of impurities due to their chemical interactions.

• Modern manufacturing employs stainless steel equipment to reduce contamination risks compared to older methods using heavy metal alloys.

Cross-contamination Risks

• Cross-contamination arises from inadequate cleaning between production batches. Residues from one batch can contaminate subsequent products if not properly managed.

• Environmental factors also contribute to contamination; personnel must maintain hygiene standards to prevent introducing pathogens during production processes.

Degradation Processes

• Primary packaging materials (glass or plastic) can leach contaminants into drugs. Additionally, degradation processes caused by moisture or metals create new compounds that act as impurities.

• Understanding the origins and classifications of impurities is essential for pharmacists to ensure medication safety and efficacy.

Classification of Impurities

• Impurities are classified based on frequency; understanding how often certain impurities occur helps in managing quality control effectively.

Impurities in Raw Materials

Common Impurities in Raw Materials

• The presence of common impurities, such as heavy metals (lead, iron, arsenic), is prevalent in most raw materials.

• Arsenic is highlighted as a common impurity resulting from organic synthesis processes.

• Specific impurities are identified within certain substances; for example, glicerophosphates are unique to glycerin and specific forms of adrenaline.

Classification of Impurities

• Impurities can be classified based on characterization techniques to definitively identify them.

• Determined impurities (like arsenic) can be investigated thoroughly, while indeterminate impurities (such as ashes or soluble residues) require general studies.

Consequences of Impurities

• Impurities may have various consequences: some are toxic, others reduce the quality of raw materials, and some cause therapeutic incompatibilities.

• Heavy metals act as catalysts that accelerate reactions and can lead to faster degradation of substances.

Identifying and Quantifying Impurities

• The concept of "quantity tolerated" refers to acceptable limits set by pharmacopoeias for raw material purity.

• This quantity tolerated is crucial for accepting or rejecting batches based on specified sensitivity limits.

Methods for Analyzing Purity

• Three methods exist for identifying and quantifying impurities: qualitative (presence/absence), semi-quantitative (e.g., tests for heavy metals), and quantitative analysis which measures both determined and indeterminate impurities rigorously.

• Rigorous quantitative criteria determine whether a batch is accepted or rejected during quality control processes.

Conclusion & Next Steps

• The session concludes with an invitation for questions about purity concepts before moving forward with future topics like adulterations. Students are encouraged to read ahead in preparation for upcoming assessments.