Demystifying the Pharmacy Abbreviation: DW vs. DAW
On a prescription bottle, particularly for liquid or compounded medications, the abbreviation 'DW' stands for distilled water. Distilled water is a highly purified form of water used as a solvent or base to dissolve an active drug, ensuring the mixture is free from minerals and contaminants that could affect the medication's stability or effectiveness. This is especially crucial for preparations that are compounded, or specially mixed, by a pharmacist to meet a patient's individual needs. Understanding the difference between 'DW' and the similar-looking 'DAW' is critical for patient safety and proper medication use.
The Role of Distilled Water in Medication
In pharmaceutical compounding, precision and purity are paramount. Using regular tap water can introduce bacteria, minerals, and other impurities that can react with the active ingredients of a medication. Distilled water, on the other hand, is water that has been boiled into vapor and then condensed back into a liquid form, leaving most contaminants behind. Its use ensures:
- Stability of the formula: Prevents unwanted chemical reactions between the drug and tap water impurities.
- Dosage accuracy: The use of a standardized, pure solvent ensures a predictable and consistent concentration of the medication.
- Reduced risk of infection: For preparations that are ingested or applied to sensitive areas, sterile distilled water minimizes the risk of introducing harmful bacteria.
Dispense as Written (DAW): A Common Point of Confusion
A far more common abbreviation on a prescription pad, and a frequent point of confusion, is 'DAW', which stands for 'Dispense as Written'. This is an instruction from the prescriber to the pharmacist specifying that no generic substitution is allowed and the brand-name drug must be dispensed. This is an important instruction related to insurance and drug costs, not the medication's ingredients. The source of confusion is often the similar appearance of the abbreviations when handwritten or misread.
There are multiple types of DAW codes, each with a specific meaning, that pharmacists use for billing and record-keeping purposes.
A Closer Look at DAW Codes
- DAW 0: No product selection indicated. The pharmacy can choose between brand and generic, usually dispensing the cheaper generic version.
- DAW 1: Substitution not allowed by the prescriber. This is what is meant when a doctor explicitly writes 'Dispense as Written' and is the most definitive instruction.
- DAW 2: Substitution allowed, but the patient requested the brand-name product.
- DAW 3: Substitution allowed, but the pharmacist selected the brand-name product.
- DAW 8: Substitution not allowed because a generic equivalent is not available on the market.
Comparison: DW vs. DAW
To help clarify the distinction, here is a comparison of 'DW' and 'DAW'.
| Feature | DW (Distilled Water) | DAW (Dispense as Written) |
|---|---|---|
| Purpose | Indicates an ingredient used as a base for liquid medications. | An instruction to the pharmacist regarding generic substitution. |
| Meaning | The solvent in which the active drug is dissolved. | The prescriber or patient requires the specific brand-name drug. |
| Context | Seen on labels for compounded liquids, solutions, or suspensions. | A common instruction on a prescription form or electronic record. |
| Appearance | May be written on the label to denote the composition of the formula. | Written or coded by the prescriber to influence the dispensing process. |
| Patient Action | No action required; informational for the patient. | May affect insurance coverage and out-of-pocket costs for the patient. |
Other Common Pharmacy Abbreviations to Know
Just as with 'DW' and 'DAW', many other abbreviations are used by healthcare professionals. Familiarity with these can improve your understanding of your medication instructions.
- a.c.: Before meals (from the Latin 'ante cibum').
- p.c.: After meals (from the Latin 'post cibum').
- b.i.d.: Twice a day (from the Latin 'bis in die').
- t.i.d.: Three times a day (from the Latin 'ter in die').
- q.i.d.: Four times a day (from the Latin 'quater in die').
- p.r.n.: As needed (from the Latin 'pro re nata').
- h.s.: At bedtime (from the Latin 'hora somni').
- p.o.: By mouth (from the Latin 'per os').
- gtt(s): Drop(s) (from the Latin 'gutta').
- c.: With (from the Latin 'cum').
- s.: Without (from the Latin 'sine').
Conclusion
While the abbreviation 'DW' on a prescription bottle is uncommon, it simply refers to distilled water, a safe and pure base for liquid medications. It's the pharmacy's way of noting the exact composition of a compounded formula. The more frequent issue is the mix-up with 'DAW', an entirely different instruction regarding brand-name versus generic drugs. Knowing the meaning of these abbreviations can help you feel more confident about your medication. However, always speak with your pharmacist if you have questions about your prescription bottle or the instructions on the label. They are the most authoritative source for verifying any information about your medication regimen.
