Difference between "controlled release" vs "prolonged release" My sister is using the epilepsy drug Tegretol which has both CR and retard (previous naming for prolonged release according to < versions in different countries. Given the active ingredient is the same (carbamazepine), would there be any difference between the effects of the two drugs in terms of preventing seizures? Here are the boxes for the two versions: ![enter image description here]( ![enter image description here](

The first box contains **Tegretol Retard** , which is an old name for what is now known as **Tegretol Prolonged Release** (medicines.org.uk).

The second box contains **Tegretol CR** , which means **controlled-release** (PubMed).

Drugs.com says:

> Your medicine is called Tegretol 200mg prolonged-release Tablets/Tegretol CR 200mg Tablets or Tegretol 400mg prolonged-release Tablets/Tegretol CR 400mg Tablets but will be referred to as Tegretol prolonged-release Tablets throughout this leaflet.

**Concluding from that, Tegretol CR200 is the same as Tegretol Retard, which is now known as Tegretol Prolonged Release.**

Saying that, it is a doctor who prescribes drugs and who can answer such questions.