Isopilocarpine is a diastereomer of pilocarpine. Isopilocarpine coexists with pilocarpine in nature and is also a degradation product of pilocarpine after oral administration to humans. It can be found in the leaves of some Pilocarpus species. Pilocarpine targets the muscarinic receptors and is approved for treatment of xerostomia. Isopilocarpine is often present in formulations of pilocarpine but has no appreciable effect on muscarinic receptors.