Question

I need to improve on a regular expression I’m using. Currently, here it is:

^[a-zA-Z\s/-]+

I’m using it to pull out medication names from a variety of formulation strings, for example:

• SULFAMETHOXAZOLE-TRIMETHOPRIM 200-40 MG/5ML PO SUSP
• AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE
• AMOXICILLIN TRIHYDRATE 125 mg ORAL TABLET, CHEWABLE
• AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE
• Amoxicillin 1000 MG / Clavulanate 62.5 MG Extended Release Tablet

The resulting matches on these examples are:

• SULFAMETHOXAZOLE-TRIMETHOPRIM
• AMOX TR/POTASSIUM CLAVULANATE
• AMOXICILLIN TRIHYDRATE
• AMOX TR/POTASSIUM CLAVULANATE
• Amoxicillin

The first four are what I want, but on the fifth, I really need “Amoxicillin / Clavulanate”.

How would I pull out patterns like “Amoxicillin / Clavulanate” (in fifth row) while missing patterns like “MG/5 ML” (in the first row)?

Update

Thanks for the help, everyone. Here’s a longer list of examples with more nuances of the data:

• Amoxicillin 1000 MG / Clavulanate 62.5 MG Extended Release Tablet
• Amoxicillin 1000 MG / Clavulanate 62.5 MG Extended Release Tablet
• Amoxicillin 10 MG/ML Oral Suspension
• Amoxil 10 MG/ML Oral Suspension
• AMOXICILLIN TRIHYDRATE 125 mg ORAL TABLET, CHEWABLE
• AMOXAPINE
• AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE
• AMOXICILLIN TRIHYDRATE 125 mg ORAL TABLET, CHEWABLE
• AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE
• AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE
• CARBATROL 200 MG PO CP12
• CARBATROL 200 MG PO CP12
• CARBATROL
• CARBAMAZEPINE 100 MG PO CHEW
• CEFDINIR 250 MG/5ML PO SUSR
• AMOXICILLIN 400 MG/5ML PO SUSR
• SULFAMETHOXAZOLE-TRIMETHOPRIM 200-40 MG/5ML PO SUSP
• DIAZEPAM 2 MG PO TABS
• DIAZEPAM
• PREDNISONE 20 MG PO TABS
• AUGMENTIN 250-62.5 MG/5ML PO SUSR
• ACETAMINOPHEN 325 MG/10.15ML PO SUSP

What I’ve done for now is this:

    private static string GetMedNameFromIncomingConceptString(string conceptAsString)
    {
        // look for match at beginning of string
        Match firstRegMatch = new Regex(@"^[a-zA-Z\s/-]+").Match(conceptAsString);
        if (firstRegMatch.Success)
        {
            // grab matching part of string as whole string
            string firstPart = conceptAsString.Substring(firstRegMatch.Index, firstRegMatch.Length);

            // look for additional match following a hash (like Amox 1000 / Clav 50)
            Match secondRegMatch = new Regex(@"/\s[a-zA-Z\s/-]+").Match(conceptAsString, firstRegMatch.Length);
            if (secondRegMatch.Success) 
                return firstPart + conceptAsString.Substring(secondRegMatch.Index, secondRegMatch.Length);
            else
                return firstPart;
        }
        else
        {
            return conceptAsString;
        }
    }

It’s pretty ugly, and I imagine it may fail when I run a lot more data through it, but it works for the larger set of cases I listed above.

Answer 1

When a slash is part of the dosage, is it always followed immediately by a digit? If so, this regex should do for you:

([A-Z]\D+)\d[^/]*(?:/\d[^/]*)*

It actively matches the dosage information as the others suggested, but captures only the medication name. Then you do a global replace for $1 to delete the dosage. Here’s how I tested it in Java:

String[] data = { 
  "SULFAMETHOXAZOLE-TRIMETHOPRIM 200-40 MG/5ML PO SUSP",
  "AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE",
  "AMOXICILLIN TRIHYDRATE 125 mg ORAL TABLET, CHEWABLE",
  "AMOX TR/POTASSIUM CLAVULANATE 125 mg-31.25 mg ORAL TABLET, CHEWABLE",
  "Amoxicillin 1000 MG / Clavulanate 62.5 MG Extended Release Tablet"
};
Pattern p = Pattern.compile("([A-Z]\\D+)\\d[^/]*(?:/\\d[^/]*)*");
Matcher m = p.matcher("");
for (String s : data)
{
  System.out.println(m.reset(s).replaceAll("$1"));
}

output:

SULFAMETHOXAZOLE-TRIMETHOPRIM
AMOX TR/POTASSIUM CLAVULANATE
AMOXICILLIN TRIHYDRATE
AMOX TR/POTASSIUM CLAVULANATE
Amoxicillin / Clavulanate

EDIT: Okay, it looks like the slash in the dosage is always followed by ML, which may be preceded by a number, which may include a decimal point. Also, the dosage information may be missing entirely. This regex seems to yield the desired result for your expanded sample input:

([A-Z]\D+)(?:$|\d[^/]*(?:/[\d.]*ML[^/]*)*)

It should work in C#, too.