Modified Release

'Modified release' means that the escape of the drug from the tablet has been modified in some way. Usually this is to slow the release of the drug so that the medicine doesn't have to be taken too often and therefore improves compliance. The other benefit from modifying release is that the drug release is controlled and there are smaller peaks and troughs in blood levels therefore reducing the chance of peak effects and increasing the likelihood of therapeutic effectiveness for longer periods of time.

Tablets and capsules which are designed to provide modified release often have the letters MR, LA, XL, CR or SR in their names e.g. Diffundox MR, Elantan LA, Dilzem XL Calcicard CR, Dilcardia S,. Sometimes the words 'slow' or 'retard' can be used to denote modified release e.g. Diclomax retard, Voltarol retard & Slow K.

There are a number of ways in which a medicine can have its release modified. Perhaps the most famous is that used in Contac 400 capsules. The pellets inside are of different thicknesses and therefore the thinnest release the drug first and the thickest last (Figure 1).

Another method used is to put the drug in thick goo which breaks down slowly itself and therefore releases the drug slowly. One method which has been tried in the past has been to put a non dissolving coating around the tablet or capsule, laser a small hole in it and then let the drug only release through the hole. In such cases patients frequently report passing the tablet or capsule whole and worrying whether it is actually working. Frequently they are however just passing the outer coat in their stools as this is how the medicine is designed to work and the drug has long been absorbed.

Modified release products usually have a higher than normal amount of the drug within them and therefore if they are crushed the whole dose will be released very quickly and could be dangerous.

For this reason modified release products should never be crushed or modified before being taken.