This blog features:
- Coding concomitant drugs in pharmacovigilance case processing
- Identifying the right WHO-DD term with accuracy and confidence
- Coding conventions: essential do’s and don’ts to avoid common errors
Table of Contents
Introduction
Concomitant drugs are one of the most frequently coded elements in case processing, alongside the suspect drug. Despite their routine nature, they are also one of the most common sources of coding errors.
Case processors often face uncertainty when selecting the correct drug code, especially when the reported information is incomplete, ambiguous, or locally branded. Incorrect coding of concomitant medications can unintentionally implicate the wrong product, distort causality assessments, and weaken overall case quality.
This guide aims to simplify the approach and help you identify and code the correct concomitant drug consistently and confidently.
What Are Concomitant Drugs?
Concomitant drugs include all medicinal products taken by the patient before, during, or after the use of the suspect drug, irrespective of their perceived relevance to the adverse event.
These include:
- Prescription medicines
- Over-the-counter (OTC) products
- Vaccines
- Herbal or traditional medicines
- Vitamins and dietary supplements
⚠️ Key principle:
Every reported concomitant drug must be captured and coded—none should be excluded based on assumptions.
“In pharmacovigilance, accuracy in concomitant drug coding is not a technical detail—it is the foundation of reliable safety data.”
Coding Standards for Concomitant Drugs
Concomitant drugs should always be coded using the WHO Drug Dictionary (WHO-DD) or another approved drug dictionary configured in the safety database.
Most safety databases globally adopt WHO-DD, which is maintained by the World Health Organization and integrated into standard pharmacovigilance workflows.
Best Practices
- Use WHO-DD consistently across the database
- Ensure dictionary version consistency within and across cases
- Avoid using internal or company-specific dictionaries for concomitant drug coding
Why Concomitant Drug Coding Feels Tricky
Coding concomitant drugs is not complicated, but it can be tricky due to:
- Incomplete product names
- Local brand variations
- Multiple strengths under the same brand name
- Country-specific formulations
Unlike suspect drugs—where detailed information is often available—concomitant drugs are frequently reported with minimal detail, increasing the risk of incorrect coding.
Identifying the Right WHO-DD Term
Choosing the exact matching term from WHO-DD is critical.
Selecting a similar-looking drug name instead of the exact reported product can:
- Attribute the case to the wrong formulation
- Introduce unnecessary drug involvement
- Compromise signal detection and data integrity
Example Scenario
Reported term: DOLO
WHO-DD entries: DOLO 650, DOLO 500, etc.
❌ Incorrect approach:
Selecting DOLO 650 without confirmation
✅ Correct approach:
If the strength is not reported, do not assume. Avoid selecting a specific strength unless it is explicitly mentioned or confirmed.
How to Handle Ambiguous or Incomplete Drug Names
When the reported drug name is unclear:
- Research the product
- Check publicly available sources
- Review product composition and available strengths
- Confirm whether multiple variants exist
- Code based on confirmed composition, not assumptions
- If uncertainty remains, document it clearly in case comments
In countries like India, the same brand name may be marketed by different companies with slight variations in strength or composition. This makes verification especially important.
Rule of thumb:
Always code what is known and confirmed, never what is assumed.
Common Mistakes to Avoid in Concomitant Drug Coding
Avoid the following frequent errors:
- Recording only suspect drugs
- Ignoring OTC, herbal, or traditional medicines
- Missing or incomplete therapy start/stop dates
- Misclassifying interacting drugs as irrelevant
- Using free-text entries instead of coded terms
- Coding concomitant drugs using a core or company-specific dictionary
Key Takeaway
Concomitant drug coding is not a secondary task—it is a core component of case quality.
Accurate, cautious, and dictionary-compliant coding protects data integrity, supports reliable causality assessment, and ensures regulatory readiness.
Where Accurate Coding Meets Regulatory Confidence
Accurate concomitant drug coding is not just about following guidelines—it’s about protecting the integrity of your safety data and regulatory submissions.
At Drugvigil, we support life sciences companies with expert pharmacovigilance services, including end-to-end case processing, WHO-DD compliant drug coding, data quality checks, and regulatory-ready safety reporting.
Conclusion
Accurate coding of concomitant drugs is a fundamental requirement for high-quality pharmacovigilance, not a routine checkbox activity. While the process may appear straightforward, incomplete product information, local brand variations, and assumptions during coding can easily compromise case integrity.
By consistently using WHO Drug Dictionary (WHO-DD), selecting only confirmed and exact terms, and strictly following established coding conventions, case processors can avoid misattribution, reduce uncertainty, and strengthen causality assessments. Special care must be taken when handling OTC products, herbal medicines, and locally marketed brands, where variations are common and assumptions are risky.
Ultimately, disciplined concomitant drug coding improves data reliability, regulatory compliance, and signal detection outcomes. A cautious, evidence-based approach—documenting what is known and clearly flagging what is unknown—ensures that each case contributes meaningfully to patient safety and public health.
Remember: In pharmacovigilance, precision in coding today prevents misinterpretation tomorrow.
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