FLUPIRTINE MALEATE
FLUPIRTINE MALEATE IS A NONOPIOID CENTRALLY-ACTING ANALGESIC AGENT, STRUCTURALLY DISSIMILAR FROM OTHER ANALGESICS. IT IS A PYRIDINE DERIVATIVE WITH THE CHEMICAL NAME OF ETHYL2AMINO6(4-FLUOROBENZYLAMINO) 3-PYRIDYLCARBAMATE MALEATE.
INDICATIONS : CLINICAL PHARMACOLOGY: PHARMACODYNAMICS:
FLUPIRTINE IS A UNIQUE CENTRALLY-ACTING, NON-OPIOID ANALGESIC WITH MUSCLE RELAXANT AND NEURO PROTECTIVE PROPERTIES. ANIMAL STUDIES HAVE DEMONSTRATED THAT FLUPIRTINE IS PREDOMINANTLY A CENTRALLY-ACTING ANALGESIC, WITH MINIMAL PERIPHERAL ANALGESIC POTENCY. ANIMAL STUDIES HAVE INDICATED THAT FLUPIRTINE LACKS ABUSE POTENTIAL AND PHYSICAL - DEPENDENCE LIABILITY. THE DRUG HAS NOT BEEN ASSOCIATED WITH SOME OF THE ADVERSE EFFECTS OF NARCOTIC ANALGESICS, AND DOES NOT APPEAR TO BE PHYSICALLY ADDICTING. THE DRUG HAS MINIMAL TO NO AFFINITY FOR OPIOID RECEPTORS, AND ANALGESIA IS NOT MEDIATED VIA OPIOID MECHANISMS. ANALGESIC EFFECTS OF FLUPIRTINE HAVE NOT BEEN ANTAGONIZED BY NALOXONE. SEROTONERQIC MECHANISMS ALSO DO NOT APPEAR TO BE INVOLVED. THE ANALGESIC EFFECTS OF FLUPIRTINE APPEAR TO BE DOSE-RELATED. FLUPIRTINE IS THE PROTOTYPE OF A CLASS OF AGENTS KNOWN AS SELECTIVE NEURONAL POTASSIUM CHANNEL OPENERS (SNEPCO). ACTIVATES G-PROTEIN- COUPLED, INWARDS ACTING K+ CHANNELS OF THE NERVE CELL: DUE TO SELECTIVE OPENING OF VOLTAGE-INDEPENDENT K+ CHANNELS AND RESULTANT OUTFLOW OF K+ CHANNELS, RESTING POTENTIAL OF THE NERVE CELL STABILIZES; THE ACTIVATION OF THE NERVE CELL MEMBRANE IS REDUCED; THE NEURON IS LESS EXCITABLE. FLUPIRTINE INDIRECTLY ACTS AS N-METHYL-D-ASPARTATE(NMDA)- ANTAGONIST; MG+2 BLOCK OF THE NMDA RECEPTOR IS NOT LIFTED UNLESS THE CELL MEMBRANE IS DEPOLARIZED. THE RESULTING NMDA ANTAGONISM OF FLUPIRTINE PROTECTS AGAINST THE INFLOW OF CA+2, SO THE SENSITIZING EFFECT OF THE RISE IN INTRACELLULAR CA+2 IS BUFFERED; AS A CONSEQUENCE, THE TRANSMISSION OF THE RISING NOCICEPTIVE IMPULSES IN A STATE OF NEURONAL EXCITATION IS THEREFORE INHIBITED. FLUPIRTINE ALSO HAS A MUSCLE-TONE NORMALIZING EFFECT ASSOCIATEDWITH THE INHIBITION OF NEURONAL TRANSMISSION TO MOTOR NEURONS AND THE RESULTING ACTION ON INTERNEURONS; THIS IS NOT A GENERAL MUSCLE-RELAXING EFFECT BUT PRIMARILY AN EFFECT LOOSENING MUSCLE TENSENESS. FLUPIRTINE NORMALISES MUSCULAR TONUS WITHOUT AFFECTING THE MUSCULAR STRENGTH. TOLERANCE TO THE ANALGESIC EFFECTS OF FLUPIRTINE HAS NOT BEEN REPORTED DURING CHRONIC USE.
PHARMACOKINETICS:
FLUPIRTINE IS WELL ABSORBED FORM THE GASTROINTESTINAL TRACT. VOLUME OF DISTRIBUTION IS ABOUT 150 L. THE APPARENT VOLUME OF DISTRIBUTION IN THE ELDERLY AND IN THOSE WITH RENAL IMPAIRMENT IS 200 L. THE MEAN PEAK SERUM CONCENTRATIONS OF FLUPIRTINE OCCUR APPROXIMATELY 1.5 TO 2 HOURS FOLLOWING ORAL ADMINISTRATION IN YOUNG AND ELDERLY SUBJECTS, AND IN PATIENTS WITH RENAL IMPAIRMENT. THE TIME TO ATTAIN PEAK LEVELS HAS BEEN LONGER (2.5 HOURS) IN PATIENTS WITH LIVER DISEASE IT IS MAINLY METABOLIZED IN LIVER. METABOLITES ARE: PARA-FLUOROHIPPURIC ACID & 2-AMINO-3-ACETYLAMMO-6-(PARA-FLUOROBENZYLAMINO) PYRIDINE. THE ACETYLATED METABOLITE HAS BEEN REPORTED TO POSSESS 20% TO 30% OF THE ANALGESIC ACTIVITY OF FLUPIRTINE. BILIARY EXCRETION MAY CONTRIBUTE TO THE ELIMINATION OF FLUPIRTINE. ELIMINATION HALF LIFE IS ABOUT 7 HOURS. IN THE ELDERLY, ELIMINATION HALF-LIFE IS 10 HOURS, AND IN THOSE WITH RENAL IMPAIRMENT, 14 TO 18 HOURS.
INDICATION & USAGE:
FLUPIRTINE IS INDICATED FOR TREATMENT OF ACUTE AND CHRONIC PAIN, I.E, FOR PAINFUL INCREASED MUSCLE TONE OF THE POSTURE AND. MOTOR MUSCLES, PRIMARY HEADACHE, TUMOR PAIN, DYSMENORRHEA AND PAIN AFTER TRAUMATOLOGIC/ ORTHOPEDIC OPERATIONS AND INJURIES.
CONTRAINDICATIONS : ESTABLISHED HYPERSENSITIVITY TO FLUPIRTINE MALEATE. FLUPIRTINE SHOULD NOT BE GIVEN TO PATIENTS AT RISK OF A HEPATIC ENCEPHALOPATHY NOR TO PATIENTS. SUFFERING FROM CHOLESTASIS, SINCE AN ENCEPHALOPATHY OR ATAXIA MAY DEVELOP OR DETERIORATE. AS FLUPIRTINE MALEATE LOOSENS MUSCLE TENSENESS PATIENTS SUFFERING FROM MYASTHENIA GRAVIS SHOULD NOT BE TREATED WITH FLUPIRTINE. SINCE FLUPIRTINE MALEATE IS MOSTLY METABOLIZED IN THE LIVER, PATIENTS WITH A LIVER DISEASE AND ALCOHOL ABUSERS SHOULD NOT BE GIVEN FLUPIRTINE.
PRECAUTION: PREGNANT & LACTATING WOMEN. NO INFORMATION CONCERNING ITS EFFECTS ON PREGNANT WOMEN IS AVAILABLE. IF THERE ARE COMPELLING REASONS FOR GIVING FLUPIRTINE TO A WOMAN BREAST-FEEDING SHOULD BE STOPPED. STUDIES HAVE SHOWN THAT A SMALL PERCENTAGE OF THE ACTIVE SUBSTANCE PASSES INTO THE MOTHER'S MILK
RENAL FAILURE:
IT IS RECOMMENDED THAT INITIAL DOSES OF FLUPIRTINE BE REDUCED BY 50% IN PATIENTS WITH EVEN MILD DEGREES OF RENAL IMPAIRMENT GERIATRIC PATIENTS: AN INCREASE IN THE ELIMINATLON HALF-LIFE OF FLUPIRTINE, ASSOCIATED WITH INCREASES IN PEAK SERUM LEVELS AND REDUCED CLEARANCE, HAS BEEN REPORTED IN ELDERLY PATIENTS AS COMPARED TO YOUNGER SUBJECTS. BASED ON THESE DATA, IT IS RECOMMENDED THAT LOWER DOSES OF FLUPIRTINE (50% OF NORMAL) BE ADMINISTERED WHEN INITIATING THERAPY IN ELDERLY PATIENTS.
SAFETY PROFILE :X
ADVERSE EFFECTS :MOST OF THE ADVERSE EFFECTS DEPENDED ON THE DOSE. IN MANY CASES THEY DISAPPEARED IN THE COURSE OF TREATMENT OR WERE REVERSIBLE AFTER THE END OF THE THERAPY. VERY FREQUENT SIDE EFFECTS (ΓβΓΒ» 10 %): TIREDNESS (ABOUT 15 PER CENT OF PATIENTS), ESPECIALLY AT THE START OF TREATMENT.
FREQUENT SIDE EFFECTS (>1 % - < 10 %): DIZZINESS, HEARTBURN, NAUSEA / VOMITING, GASTRIC DISORDERS, CONSTIPATION, DISTURBED SLEEP, OUTBREAK OF SWEAT, LACK OF APPETITE, DEPRESSION, TREMOR, HEADACHE, ABDOMINAL PAIN, DRYNESS OF THE MOUTH, RESTLESSNESS / NERVOUSNESS, FLATULENCE, DIARRHEA OCCASIONAL SIDE EFFECTS (> 0.1 % - < 1 %):CONFUSION, VISUAL DISTURBANCES AND ALLERGIC REACTIONS. ALLERGIC REACTIONS, IN ISOLATED CASES WITH A RAISED BODY TEMPERATURE, MANIFESTED THEMSELVES IN SYMPTOMS SUCH AS RASH, URTICARIA AND ITCHING. VERY RARE SIDE EFFECTS ΓβΓΒ« 0.01 %): IN VERY RARE AND ISOLATED CASES REPORTS ABOUT THE APPLICATION OF THE DRUG IN PRACTICE REFERRED TO SIDE EFFECTS AFFECTING THE LIVER: INCREASES IN TRANSAMINASE (WHICH MOSTLY NORMALIZED AFTER A DOSE REDUCTION OR DISCONTINUATION OF FLUPIRTINE MALEATE), DRUG INDUCED HEPATITIS (ACUTE OR CHRONIC, ICTERIC OR ANICTERIC, WITH OR WITHOUT A CHOLESTATIC ELEMENT). IN VERY FEW CASES WITH CLINICAL SYMPTOMS THE LIVER WAS EITHER DAMAGED BEFORE OR A CO-MEDICATION AFFECTING THE LIVER FUNCTION WAS GIVEN.
DRUG INTERACTIONS : FLUPIRTINE MAY INTERACT WITH ANTICOAGULANTS SUCH AS WARFARIN. A BLOOD TEST CALLED THE PT IS NEEDED TO MONITOR THIS POTENTIAL INTERACTION. ALCOHOL OR OTHER SEDATIVES SUCH AS BENZODIAZEPINES CAN INCREASE THE TIREDNESS AND DIZZINESS THAT YOU MAY EXPERIENCE WITH FLUPIRTINE.
DOSAGE :DOSE & ADMINISTRATION:
FLUPIRTINE CAPSULE IS FOR ORAL ADMINISTRATION WITH THE FOLLOWING DOSAGE AS REGIMEN. INITIALLY TWO CAPSULES DEPENDING ON DIAGNOSIS AND PAIN INTENSITY. AFTERWARDS ONE CAPSULE ORALLY 3 - 4 TIMES A DAY.CHILDREN (OLDER THAN SIX YEARS) HAVE BEEN TREATED WITH 50 MILLIGRAMS ORALLY THREE OR FOUR TIMES DAILY FOR UP TO SIX DOSES PER DAY.
RENAL IMPAIRMENT : IT IS RECOMMENDED THAT INITIAL DOSES OF FLUPIRTINE BE REDUCED BY 50% IN PATIENTS. WITH EVEN MILD DEGREES OF RENAL IMPAIRMENT GERIATRIC PATIENTS: AN INCREASE IN THE ELIMINATION HALF-LIFE OF FLUPIRTINE, ASSOCIATED WITH INCREASES IN PEAK SERUM LEVELS AND REDUCED CLEARANCE, HAS BEEN REPORTED IN ELDERLY PATIENTS AS COMPARED TO YOUNGER SUBJECTS. BASED ON THESE DATA, IT IS RECOMMENDED THAT LOWER DOSES OF FLUPIRTINE (50% OF NORMAL) BE ADMINISTERED WHEN INITIATING THERAPY IN ELDERLY PATIENTS.
REMARK :STORAGE: STORE IN A COOL AND DRY PLACE PROTECTED FROM LIGHT AND MOISTURE