Despite this, 4-AP has beneficial effects on spasticity. 4-AP reacts with many different kinds of fillers, leading to a shortened shelf life and lower potency. For example, some formulations of 4-AP may lose as much as 10 to 20 percent of its potency per week. It is likely that many of the 4-AP pills out there do not have the potency that they are said to have. In addition, the immediate-release formulation results in a peak plasma dose within 30 minutes.
Plasma levels fall by about a half within three to four hours.
Immediate-release formulations therefore tend to produce higher peak levels and greater variations in plasma levels. Peak levels determine side effects, one of the reasons why a sustained or timed-release formulation of the drug is desirable. This formulation has not yet been approved by the FDA and therefore is not available. That version of the drug is currently undergoing phase 2 clinical trials. Click here for more information.