Isosorbide mononitrate is a nitrate used for the prevention of angina. It is presented only as a sustained release preparation and, therefore, cannot be crushed or chewed.

Isosorbide mononitrate is available in both 60mg and 120mg formulations, and daily dosing ranges from 30mg to 120mg.

The 120mg tablets (Imdur®, Monodur®) are not scored and should not be administered in half doses.

The 60mg tablets (Chemmart®, Duride®, GenRx®, Imdur®, Imtrate® SR, Isomonit®, Isosorbide AN®, Monodur®, Terry White Chemists®) are scored. However, not all brands can be halved.

Duride®, Imdur® and Monodur® are the only brands where the sustain-release properties are not compromised when the tablet is halved for 30mg doses.

There is insufficient evidence to demonstrate that one halved tablet of the Chemmart®, GenRx®, Imtrate® SR, Isomonit®, Isosorbide AN® and Terry White Chemists® brands deliver exactly half the dose of a full tablet, or whether the rate of release is the same. In-vitro dissolution testing has demonstrated the dissolution was slightly faster with halved tablets compared to a whole tablet.

It is important to recognise that while many tablets are scored, not all can be halved. Particular attention should be given when dispensing or administering isosorbide mononitrate, wherein 30mg doses, only Duride®, Imdur® and Monodur® 60mg tablets can be halved safely.

References:

  1. Duride 60mg (Isosorbide mononitrate) Australian approved product information. Millers Point: Alphapharm Pty Ltd. Approved 18 September 2013
  2. Imdur Durules 60mg (Isosorbide mononitrate) Australian approved product information. North Ryde: AstraZeneca Pty Ltd. Approved 3 May 2006
  3. Monodur Durules 60mg (Isosorbide mononitrate) Australian approved product information. North Ryde: PMC Pharma. Approved 3 May 2006
  4. GenRx Isosorbide Mononitrate 60mg (Isosorbide mononitrate) Australian approved product information. Macquarie Park: Apotex Pty Ltd. Approved 4 November 2008
  5. Chemmart Isosorbide Mononitrate 60mg (Isosorbide mononitrate) Australian approved product information. Macquarie Park: Apotex Pty Ltd. Approved 4 November 2008
  6. Imtrate SR 60mg (Isosorbide mononitrate) Australian approved product information. South Melbourne: Ascent Pharma Pty Ltd. Approved 15 April 2010
  7. Isomonit 60mg (Isosorbide mononitrate) Australian approved product information. Pyrmont: Sandoz Pty Ltd. Approved 27 February 2012
  8. Isosorbide AN 60mg (Isosorbide mononitrate) Australian approved product information. South Yarra: Amneal Pharma Australia Pty Ltd. Approved 9 July 2014.

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