Names and pronunciation
(peer-id-oh-stig′meen) Mestinon, Mestinon SR , Mestinon Tinespan, Regonol
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Drug reference
(peer-id-oh-stig′meen) Mestinon, Mestinon SR , Mestinon Tinespan, Regonol
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Func. class.: Cholinergic; anticho- linesterase Func. class.: Vit B6, water soluble
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Chem. class.: Tertiary amine carbamate
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ACTION: Inhibits destruction of acetylcholine, which increases concen tration at sites where acetylcholine is released; this facilitates the transmission of impulses across the myoneural junction ACTION: Needed for fat, protein, carbohydrate metabolism; enhances glycogen release from liver and muscle tissue; needed as coenzyme for metabolic transformations of a variety of amino acids
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USES: Nondepolarizing muscle relaxant antagonist, myasthenia gravis, pretreatment for nerve gas exposure (military only) USES: Vit B6 deficiency of inborn errors of metabolism, seizures, isoniazid therapy, oral contraceptives, alcoholic polyneuritis
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Do not confuse: pyridoxine/Pyridium
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CONTRAINDICATIONS: Brady cardia; hypotension; obstruction of intes tine, renal system; bromide, benzyl alcohol sensitivity; adrenal insufficiency; cholinesterase inhibitor toxicity Precautions: Pregnancy, seizure disor- ders, bronchial asthma, coronary occlu- sion, hyperthyroidism, dysrhythmias, peptic ulcer, megacolon, poor GI motility CONTRAINDICATIONS: Hyper sensitivity Precautions: Pregnancy, breastfeeding, children, Parkinson’s disease; patients taking levodopa should avoid supple- mental vitamins with >5 mg pyridoxine
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SIDE EFFECTS CNS: Dizziness, headache, sweating, weakness, seizures, incoordination, paralysis, drowsiness, LOC CV: Tachycardia, dysrhythmias, brady- cardia, AV block, hypotension, ECG changes, cardiac arrest, syncope EENT: Miosis, blurred vision, lacrima- tion, visual changes GI: Nausea, diarrhea, vomiting, cramps, increased salivary and gastric secretions, peristalsis GU: Urinary frequency, incontinence, urgency INTEG: Rash, urticaria, flushing RESP: Respiratory depression, broncho- spasm, constriction, laryngospasm, respi- ratory arrest SYST: Cholinergic crisis SIDE EFFECTS CNS: Paresthesia, flushing, warmth, lethargy (rare with normal renal function) INTEG: Pain at inj site
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INTERACTIONS Increase: action—succinylcholine Decrease: action—gallamine, metocurine, pancuronium, tubocurarine, atropine Decrease: pyridostigmine action—ami- noglycosides, anesthetics, procainamide, quiNIDine, mecamylamine, polymyxin, magnesium, corticosteroids, antidys- rhythmics, quinolones INTERACTIONS Decrease: effects of levodopa Decrease: effects of pyridoxine—oral contraceptives, isoniazid, cycloSERINE, hydrALAZINE, penicillamine, chloram- phenicol, immunosuppressants P
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TREATMENT OF OVERDOSE: Discontinue product, atropine 1-4 mg IV OTC) (peer-i-dox′een) Cataplex , Pyri 500, Neuro-K
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DOSAGE AND ROUTES Myasthenia gravis • Adult: PO 600 mg/day in 5-6 divided doses, max 1.5 g/day; IM/IV 2 mg; SUS REL 180-540 mg/day or bid at intervals of ≥6 hr • Child: PO 7 mg/kg/day in 5-6 divided doses; IM/IV 0.05-0.15 mg/kg/dose Nondepolarizing neuromuscular blocker antagonist • Adult: 0.6-1.2 mg IV atropine, then 0.1-0.25 mg/kg/dose • Child: IV 0.1-0.25 mg/kg/dose P Nerve gas exposure prophylaxis (military) • Adult: PO 30 mg q8hr if threat of ex- posure to Soman gas is anticipated; start several hours before exposure and dis- continue upon exposure; after product is discontinued, give antidotes (atropine, pralidoxime) DOSAGE AND ROUTES RDA • Adult: PO (male) 1.7-2 mg; (female) 1.4-1.6 mg • Child 9-13 yr: PO 1 mg/day • Child 4-8 yr: PO 0.6 mg/day • Child 1-3 yr: PO 0.5 mg/day • Infant 7-12 mo: PO 0.3 mg/day Vit B6 deficiency • Adult: PO 5-25 mg/day × 3 wk • Child: PO 10 mg until desired response Pyridoxine deficiency neuritis/ seizure (not drug induced) • Adult: PO without neuritis 2.5-10 mg/ day, after corrected 2-5 mg/day; with neuritis 100-200 mg/day × 3wk, then 2-5 mg/day • Child: PO without neuritis 5-25 mg/ day × 3wk, then 1.5-2.5 mg/day in a multivitamin; with neuritis: 10-50 mg/ day × 3wk, then 1-2 mg/day • Neonate with seizures: IM/IV 50-100 mg as single dose Deficiency caused by isoniazid, cycloSERINE, hydrALAZINE, penicillAMINE • Adult: PO 100-300 mg/day • Child: PO 10-50 mg/day Prevention of deficiency caused by isoniazid, cycloSERINE, hydrALAZINE, penicillAMINE • Adult: PO 25-100 mg/day • Child: PO 1-2 mg/kg/day
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Available forms: Tabs 60 mg; ext rel tabs 180 mg; syr 60 mg/5 mL; inj 5 mg/mL Available forms: Tabs 25, 50, 100, 250, 500 mg; ext rel tabs 200, 500 mg; inj 100 mg/mL; ext rel caps 200, 500 mg; capsules 250 mg
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Administer: • Only with atropine sulfate available for cholinergic crisis • Only after all other cholinergics have been discontinued • Increased doses for tolerance as or- dered • Larger doses after exercise or fatigue as ordered • Do not break, crush, or chew sus rel tabs PO route • On empty stomach for better absorp- tion Direct IV route • Undiluted (5 mg/mL), give through Y- tube or 3-way stopcock, give ≤0.5 mg/ min (myasthenia gravis); 5 mg/min (re- versal of nondepolarizing neuromuscular blockers) Y-site compatibilities: Heparin, hydro- cortisone, potassium chloride, vit B/C Administer: PO route • Do not break, crush, or chew ext rel tabs/caps IM route • Rotate sites; burning or stinging at site may occur • Z-track to minimize pain IV route • Undiluted or added to most IV sol; give ≤50 mg/1 min if undiluted Syringe compatibilities: Doxapram
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Assess: • Myasthenia gravis: fatigue, ptosis, dip- lopia, difficulty swallowing, SOB, hand/ gait before, after product; improvement should be seen after 1 hr • VS, respiration q8hr • I&O ratio; check for urinary retention or incontinence • Toxicity: bradycardia, hypotension, bronchospasm, headache, dizziness, sei- zures, respiratory depression; product should be discontinued if toxicity occurs • Pregnancy/breastfeeding: use only if benefits outweigh fetal risk; cautious use in breastfeeding Assess: • Pyridoxine deficiency: seizures, irrita- bility, cheilitis, conjunctivitis, anemia, confusion, red tongue, weakness, fatigue before and during treatment; monitor pyridoxine levels • Nutritional status: yeast, liver, legumes, bananas, green vegetables, whole grains • Blood studies: Hct, HB • Malabsorption: may require injection if abdominal resection has occurred or in malabsorption syndromes • Pregnancy/breastfeeding: safe in preg- nancy, breastfeeding
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Evaluate: • Therapeutic response: increased muscle strength, hand grasp, improved gait, absence of labored breathing (if severe), negative in- spiratory force, and vital capacity; reversal of nondepolarizing neuromuscular blockers; prevention of nerve gas toxicity Evaluate: • Therapeutic response: absence of nau- sea, vomiting, anorexia, skin lesions, glossitis, stomatitis, edema, seizures, restlessness, paresthesia
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CLINICAL CONSIDERATIONS CLINICAL CONSIDERATIONS
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Patient and caregiver information: • Myasthenia gravis: that product is not a cure, only relieves symptoms • To wear emergency ID specifying my- asthenia gravis, products taken • To avoid driving, other hazardous ac- tivities until effect is known • To report muscle weakness (choliner- gic crisis or underdosage), bradycardia • Not to drink alcohol • To take with food to decrease gastric side effects • That doses are highly individualized, often 5-6 times per day, and will be based on response to the product Patient and caregiver information: • To avoid vitamin supplements unless directed by prescriber • To increase meat, bananas, potatoes, lima beans, whole-grain cereals in diet • To take as directed; to continue with follow-up exams, blood work
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PHARMACOKINETICS Metabolized in liver, excreted in urine (unchanged) PO: Onset 20-30 min, duration 3-6 hr PO-EXT REL: Onset 30-60 min, duration 6-12 hr IM/IV/SUBCUT: Onset 2-15 min, dura- tion 21/2-4 hr PHARMACOKINETICS PO/INJ: Half-life 2-3 wk, metabolized in liver, excreted in urine
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• Infant 7-12 mo: PO 0.3 mg/day Vit B6 deficiency
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