OpenAHLTA was created from AHLTA-Theater but we removed all of the costly proprietary modules in order to keep it free. The Drug-to-drug interaction checking is now optional, not required. For example, if you purchase the FDB MedKnowledge product, OpenAHLTA will automatically perform Drug-to-Drug and Drug-to-Allergy interaction checking. Below is a list of changes from AHLTA-Theater.

• Uses SNOMED-CT (the most comprehensive, multilingual clinical healthcare terminology in the world)
• The History and physical MEDCIN tree has been replaced with free text
  • Use dragon natually speaking to dictate your own encounter note
  • Use asutype for mistake-free, fast typing
• Contains free crystal reports for local reporting
• Immunizations module is enabled!
• The Dental modues exist but are disabled for the first release
• The Oracle database has been replace with MySQL
• The Medcin ICD terminology has been replaced with SNOMED-CT