Drug Topics - February 2009 - (Page 45)

CONTINUING EDUCATION Peak plasma concentrations occur 1 to 4 hours after oral administration. The elimination half-life is approximately 13 hours. The oral and intravenous formulations are bioequivalent, so there is no need to adjust the dose when converting from IV to oral therapy. Precautions: As with other antiepileptics, lacosamide increases the risk of suicidal thoughts and behaviors; patients should be monitored accordingly. Also as with other antiepileptic medications, lacosamide should be tapered to discontinuation to prevent the risk of increased seizure frequency. Drug interactions: Studies revealed no signiﬁcant drug interactions, but caution is advised when lacosamide is administered with drugs that may affect the heart conduction system (e.g., drugs that may prolong the QT interval). Adverse effects: The adverse reactions most commonly leading to drug discontinuation were dizziness, nausea, vomiting, diplopia, blurred vision, ataxia, and vertigo. Elevations in liver enzymes were observed in some cases during clinical trials. Dosage and availability: The initial recommended oral starting dose is 50 mg taken twice daily. The dose may be increased by weekly intervals of 100 mg/day until the recommended dose of 200 to 400 mg/day has been reached. A maximum dose of 300 mg/day is recommended in patients with severe renal impairment or mild-to-moderate hepatic impairment. Lacosamide is available as 50-, 100-, 150-, and 200-mg tablets as well as in a 200-mg/20-mL single-use vial for intravenous use. Patient counseling: Patients should be advised to be aware of any changes in moods, behaviors, thoughts, or feelings. Lacosamide may be taken without regard to meals. Instruct the patient not to stop taking the medicine abruptly. METHYLNALTREXONE (Relistor, Progenics). FDA rating: 1-S,I. Methylnaltrexone is the second approved peripherally acting mu-opioid receptor antagonist. When standard therapy is unsuccessful at treating opioid-induced constipation in patients receiving palliative care, it offers a therapeutic alternative. Indication: Methylnaltrexone is indicated for the treatment of opioid-induced constipation in patients with advanced illness who are receiving palliative care, when response to laxative therapy has not been sufﬁcient. Pharmacology: Methylnaltrexone is a peripherally acting, selective antagonist of opioid binding at the mu-opioid receptor. It does not have an impact on opioid-mediated analgesic effects on the central nervous system because its structure restricts it from crossing the blood-brain barrier. It exerts its effect by antagonizing opioid receptors in the gastrointestinal tract. Precautions: Patients with known or suspected mechanical gastrointestinal obstruction should not receive methylnaltrexone. Adverse effects: Methylnaltrexone was generally well tolerated in trials. The most common adverse reactions reported with methylnaltrexone are abdominal pain, ﬂatulence, nausea, dizziness, and diarrhea. Dosage and availability: Methylnaltrexone is administered W W W.D R U GTO P I C S .C O M as a subcutaneous injection. The usual schedule is 1 dose every other day as needed, but no more frequently than 1 dose in a 24-hour period. The recommended dose of methylnaltrexone is 8 mg for patients weighing 38 to less than 62 kg (84 to less than 136 lb) or 12 mg for patients weighing 62 to 114 kg (136 to 251 lb). Patients whose weight falls outside these ranges should be dosed at 0.15 mg/kg. Methylnaltrexone is available as a 12 mg/0.6 mL solution for injection in single-use vials. Patient counseling: Tell patients that methylnaltrexone is used to treat constipation caused by prescription pain medicines taken by patients receiving supportive care for advanced illness, when other medications for constipation have not worked well enough. Stipulate that only 1 dose of naltrexone should be administered in any 24-hour period. Explain that laxation can occur within 30 minutes and emphasize the importance of being in close proximity to toilet facilities after the drug is administered. Advise patients that methylnaltrexone should be stored away from light. Stress the importance of injection-site rotation. Instruct patients to read the patient information leaﬂet to reinforce what you have discussed. REGADENOSON (Lexiscan, Astellas). FDA rating = 1-S,I. Regadenoson is a novel adenosine receptor agonist with selectivity for the A2A adenosine receptor. Its safety and efﬁcacy are similar to those of adenosine (the other member of its class), but its ease of administration is a potential advantage. Indication: Regadenoson is a pharmacologic stress agent indicated for radionuclide myocardial perfusion imaging (MPI) in patients unable to undergo adequate exercise stress. Pharmacology: Regadenoson produces coronary vasodilation and increased coronary blood ﬂow by activating the A2A adenosine receptor. In vitro, its afﬁnity for the A2B and A3 adenosine receptors, which have been implicated in the pathophysiology of bronchoconstriction in susceptible individuals (i.e., asthmatics), is minimal. Adverse effects: When regadenoson and adenosine, a nonspeciﬁc adenosine receptor agonist, were studied head to head, adverse reactions occurred at similar rates in the two groups. Dosage and availability: The recommended dose of regadenoson is 5 mL (0.4 mg) administered by rapid intravenous injection. It should be followed immediately by saline ﬂush and radiopharmaceutical. RUFINAMIDE (Banzel, Eisai). FDA Rating: 1-S,O,T. Lennox-Gastaut syndrome (LGS) is a severe form of childhood epilepsy that is poorly controlled by current anticonvulsant measures. Ruﬁnamide is another treatment option for this disorder. Indications: Ruﬁnamide is indicated for use as adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in adults and children aged 4 years and older. Pharmacology and pharmacokinetics: Similar to lacosamide, in vitro data suggest anticonvulsant properties are exerted through prolonging the inactive state of sodium channels in the brain. This occurs by slowing the sodium channel recovery from inactivation and limiting sustained repetitive ﬁring of sodium-dependent action potentials. Februar y 2009 DRUG TOPICS 45 http://WWW.DRUGTOPICS.COM

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Drug Topics - February 2009 Contents Health-System Edition Group Attempts to Resurrect Pain Care Act HSE Business Management HSE Clinical Letters Up Front Up Front in Depth Community Practice Niche Pharmacies Serve Special Populations Special Report Oral Oncology Drugs New Drugs Update 2008 Approvals OTC New Products Viewpoint

Drug Topics - February 2009

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