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What is "dual release" nitrofurantoin?

In the nitrofurantoin dosage information, it refers to "regular release" and "dual release" formulations of nitrofurantoin. What is the difference?

Medically reviewed by Last updated on May 20, 2019.

Official Answer


Dual release nitrofurantoin refers to the nitrofurantoin monohydrate/macrocrystalline nitrofurantoin capsule formulation, which is available under the brand name Macrobid and its generics.

Nitrofurantoin is an antibacterial agent specific for the treatment of urinary tract infections.

Nitrofurantoin capsules are available in two formulations: 

  • Macrodantin and its generics which contain macrocrystalline nitrofurantoin.
  • Macrobid and its generics which contain nitrofurantoin monohydrate and macrocrystalline nitrofurantoin.

Macrocrystalline nitrofurantoin (Macrodantin) is sometimes referred to as regular release nitrofurantoin.

Nitrofurantoin monohydrate/macrocrystalline nitrofurantoin (Macrobid) is sometimes referred to as dual release nitrofurantoin.

The dual release nitrofurantoin formulation contains both the regular release macrocrystalline nitrofurantoin, and nitrofurantoin monohydrate. The nitrofurantoin monohydrate powder blend in the capsule forms a gel matrix upon exposure to gastric and intestinal fluids, allowing the nitrofurantoin to be released slowly over time and a providing longer dosing interval of twice a day, compared to four times a day with the regular release formulation .

In the treatment of urinary tract infections (cystitis):

  • regular release nitrofurantoin is dosed four times a day
  • dual release nitrofurantoin is dosed twice a day.

For the prevention of urinary tract infections

  • regular release nitrofurantoin is dosed once a day.

For more information, see Nitrofurantoin Dosage.

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