Such a combination will produce a lesser degree of analgesia than the opioid alone. Adjuvant analgesics are the many types of medication that may help specific types of pain. Skeletal muscle relaxants and antispasmodics act directly on muscle spasms, an often-overlooked source of pain for many individuals. Other adjuvant analgesics that have application for specific pain syndromes include clonidine, mexiletine, neuroleptics, and psychostimulants. Used for pain, it is best dosed three to four times per day.
Meperidine is very problematic when used chronically.
Meperidine metabolism produces normeperidine, a long-lived central nervous system irritant with no analgesic value. As normeperidine accumulates in the blood, patients begin to experience emotional lability, irritability, myoclonus, and, when the level becomes sufficiently high, seizures. Thus, it is recommended that meperidine be used for no more than 48 hours, and at doses lower than 600 mg per day in individuals with good renal function. Unfortunately, these medications have proven to be more problematic than helpful when used chronically. They are every bit as susceptible to abuse as pure agonists such as morphine, have a high incidence of psychotomimetic effects, and display a ceiling to their effective dose.