Profound Pain Reduction After Induction of Memantine Treatment in Two Patients with Severe Phantom Limb Pain

In Brief We present the cases of two patients who suffered severe lower extremity injuries and subsequently developed phantom limb pain (PLP) that was refractory to high dose opioids and adjunctive pain medications. Both patients were receiving large doses of oral methadone, IV hydromorphone via a patient-controlled analgesia delivery system, and adjunctive medications including tricyclic antidepressants, nonsteroidal anti-inflammatory medications, and anti-epileptics. Despite these treatments, the patients had severe PLP. Upon induction of the oral N-methyl-d-aspartate receptor antagonist memantine, both patients had a profound reduction in their PLP without any apparent side effects from the medication. IMPLICATIONS: The administration of memantine to two patients with severe refractory phantom limb pain led to a significant reduction in pain. In patients with refractory phantom pain, memantine may be considered as an additional adjunctive medication.