ABSTRACT
Abuse of a dangerous street drug called mephedrone (4-methylmethcathinone) has become commonplace in the United States. Mephedrone is hypothesized to possess abuse liability, share pharmacological properties with psychostimulants, and display toxicity that has been linked to fatalities and non-fatal overdoses. Knowledge about the pharmacology of mephedrone has been obtained primarily from surveys of drug abusers and emergency room visits rather than experimental studies. The present study used motor activity and conditioned place preference (CPP) assays to investigate behavioral effects of mephedrone. Acute mephedrone (3, 5, 10, 30 mg/kg, ip) administration increased ambulatory activity in rats. Mephedrone (5 mg/kg, ip)-induced ambulation was inhibited by pretreatment with a dopamine D1 receptor antagonist (SCH 23390) (0.5, 1, 2 mg/kg, ip) and enhanced by pretreatment with a dopamine D2 receptor antagonist (sulpiride) (2 mg/kg, ip). Rats injected for 5 days with low dose mephedrone (0.5 mg/kg, ip) and then challenged with mephedrone (0.5 mg/kg, ip) following 10 days of abstinence displayed sensitization of ambulatory activity. In CPP experiments, mephedrone (30 mg/kg, ip) conditioning elicited a preference shift in both rats and mice. The CPP and dopamine-sensitive motor activation produced by mephedrone is suggestive of abuse liability and indicates commonalities between the neuropharmacological profiles of mephedrone and established drugs of abuse.
Subject(s)
Central Nervous System Stimulants/pharmacology , Conditioning, Operant/drug effects , Dopamine/physiology , Methamphetamine/analogs & derivatives , Motor Activity/drug effects , Animals , Benzazepines/pharmacology , Dopamine Antagonists/pharmacology , Dopamine D2 Receptor Antagonists , Male , Methamphetamine/pharmacology , Mice , Rats , Rats, Sprague-Dawley , Receptors, Dopamine D1/antagonists & inhibitors , Receptors, Dopamine D1/drug effects , Receptors, Dopamine D2/drug effects , Sulpiride/pharmacologyABSTRACT
INTRODUCTION: d-Propoxyphene, which was previously available in many single-agent and combination products, was recently voluntarily withdrawn from the US market following an FDA recommendation based partly on the concern that the risk associated with QT prolongation exceeded the clinical benefit of the drug. The drug had previously been withdrawn from European markets. These recent actions prompt the question: what is known about QT prolongation and analgesic drugs? AREAS COVERED: A systematic search was conducted of 50 opioid and non-opioid analgesic drugs using PubMed, the FDA website, and the Internet. Search terms for opioids, NSAIDs, acetaminophen and other analgesics were used (including both generic and brand names), along with QTc, QTc prolongation, QTc interval, hERG, torsades de pointes (TdP), ventricular arrhythmias, and other relevant terms. EXPERT OPINION: There is a paucity of available information on the QT interval for most analgesics. Of those for which there is a lot of data, only methadone, oxycodone, and LAAM (levo--acetylmethadol) appear to have a known and accepted level of effect on the QT interval.
