Antagonism of acute cocaine toxicity by buprenorphine

Buprenorphine: considerations for pain management

New effective analgesics are needed for the treatment of pain. Buprenorphine, a partial mu-opioid agonist which has been in clinical use for over 25 years, has been found to be amenable to new formulation technology based on its physiochemical and pharmacological profile. Buprenorphine is marketed as parenteral, sublingual, and transdermal formulations. Unlike full mu-opioid agonists, at higher doses, buprenorphine's physiological and subjective effects, including euphoria, reach a plateau. This ceiling may limit the abuse potential and may result in a wider safety margin. Buprenorphine has been used for the treatment of acute and chronic pain, as a supplement to anesthesia, and for behavioral and psychiatric disorders including treatment for opioid addiction. Prolonged use of buprenorphine can result in physical dependence. However, withdrawal symptoms appear to be mild to moderate in intensity compared with those of full mu agonists. Overdoses have primarily involved buprenorphine taken in combination with other central nervous system depressants.

Cardiovascular disorders associated with cocaine use: myths and truths

Cocaine produces a pattern of cardiovascular responses that are associated with apparent myocardial ischemia, arrhythmias, and other life-threatening complications in some individuals. Despite recent efforts to better understand the causes of cocaine-induced cardiovascular dysfunction, there remain a number of unanswered questions regarding the specific mechanisms by which cocaine elicits hemodynamic responses. This review will describe the actions of cocaine on the cardiovascular system and the evidence for the mechanisms by which cocaine elicits hemodynamic and pathologic responses in humans and animals. The emphasis will be on experimental data that provide the basis for our understanding of the mechanisms of cardiovascular toxicity associated with cocaine. More importantly, this review will identify several controversies regarding the causes of cocaine-induced cardiovascular toxicity that as yet are still debated. The evidence supporting these findings will be described. Finally, this review will outline the obvious deficits in our current concepts regarding the cardiovascular actions of cocaine in hope of encouraging additional studies on this grave problem in our society.

Antidotal effects of buprenorphine on the behavioral alterations accompanying cocaine and combined cocaine-ethanol toxicity

The present study examined the effects of buprenorphine (BUP), a mixed opioid agonist-antagonist, on the behaviors accompanying cocaine (COCA) and combined cocaine-ethanol (EtOH) toxicity in the surviving mice. Using the activity-counting instrument Supermex, the relationship between the toxic signs and the corresponding behavioral alterations could be assessed. In the COCA-only group, a prolonged increase in the activity counts was caused by a high dose of COCA (75 mg/kg ip). Furthermore, this COCA-induced hyperactivity included ataxic behaviors that were accompanied by visible toxic signs, which were not observed in the mice with no drug treatment. A depressive dose of EtOH (3 g/kg ip) did not significantly modify the mortality rate in the COCA-only group in spite of its anticonvulsant effects. However, the peak activity counts in the survivors were attenuated in the COCA-EtOH group as compared to the COCA-only group. BUP attenuated the mortality rate in both COCA and COCA-EtOH groups, even without any anticonvulsant effects, but the most effective dose differed between the COCA (BUP: 0.25 mg/kg ip) and COCA-EtOH (BUP: 0.5 mg/kg ip) groups. At these BUP doses, the prolonged suppression of the morbid hyperactivity in the COCA-BUP group and the restoration of normal behavior in the COCA-EtOH-BUP group both seemed to be correlated with a good prognosis in the survivors; there was an early recovery from an increased blood pressure (BP), increased heart rate (HR) and decreased respiratory rate (RR) in the COCA-BUP group, and an early recovery from a decreased BP, decreased HR and decreased RR in the COCA-EtOH-BUP group.

Comparison of effect of ethanol and anticonvulsants on cardiovascular drug-modified cocaine toxicity

The anticonvulsant (AC drug)- or ethanol (EtOH)-modified effects of cardiovascular (CV) drugs against cocaine (COCA)-induced toxicity were examined in male ICR mice. Nontoxic doses of the CV drugs nimodipine (NIMO), prazosin (PRA), phentolamine (PHEN), propranolol (PRO), and enalapril (ENA) were used with or without the AC drugs diazepam (DZP), phenobarbital (PHB), phenytoin (PHY), and EtOH. Each CV drug combined with or without each AC drug was administered intraperitoneally (IP) 5 min before an IP injection of COCA 75 mg/kg. Of the CV drugs examined, PRA 5 mg/kg and PHEN 5 mg/kg protected against COCA-induced seizures, but only the alpha1-adrenergic blocking agent PRA protected against COCA-induced deaths. Of the AC drugs examined, DZP 5 mg/kg and PHB 50 mg/kg, as well as EtOH 3 g/kg, attenuated the severity of the COCA-induced seizures, but only PHB protected against COCA-induced deaths. The total mortality rate was significantly, often synergistically, decreased compared to the COCA-only group when the appropriate CV drugs were combined with the AC drugs: PRA 5 mg/kg in the EtOH-cotreated groups, PRA 5 mg/kg, PHEN 5 mg/kg or ENA 10 mg/kg in the DZP-cotreated groups, and NIMO 5 mg/kg, PRA 5 mg/kg, PHEN 5 mg/kg, or PRO 10 mg/kg in the PHB-cotreated groups. The decrease in the COCA concentration in the blood and/or brain was not always accompanied by an attenuation of the mortality rate. However, the attenuation of severe seizures by a single PRA, PHEN, DZP, or PHB cotreatment was accompanied by a decrease in the brain COCA concentration.

Voltammetric study and determination of buprenorphine in pharmaceuticals

The oxidation of buprenorphine on a carbon paste electrode has been studied using voltammetric techniques under both semi-infinite linear diffusion and hydrodynamic conditions. By applying a simple electrode pretreatment a good reproducibility of the current signal is obtained (R.S.D. = 0.85%, n = 6 for a 1.0 x 10(-5) M buprenorphine concentration). The limit of detection was found to be 2.0 x 10(-7) M. The voltammetric method developed for the determination of buprenorphine in pharmaceutical preparations was examined for its applicability to liquid and solid preparations.

The thymolytic effect of cocaine and monoaminergic drugs in the mouse

Cocaine abuse is known to be associated with suppression of the immune system. In this experiment, animals treated with cocaine (CC) in their drinking water (200 mg/L) for 10 days resulted in a significant decrease in thymus weight in HSD-NDA male Swiss mice. A subsequent in-vitro experiment was designed to investigate the direct effect of cocaine and other dopaminergic agents on thymocyte proliferation. Thymus glands were aseptically removed from mice and thymocytes were isolated and then incubated in microtiter plates with various concentrations (10[-8]-10[-4] M) of CC, apomorphine (AM), haloperidol (HP), dopamine (DA) and epinephrine (EN) for 18 hrs. The results revealed that cocaine inhibits [3H]-thymidine uptake into DNA in a dose-dependent manner. Apomorphine, haloperidol and dopamine also exhibited a similar dose dependent inhibition of thymocyte proliferation. The IC25s for DNA synthesis inhibition were 8.2 x 10(-6) M, 4.3 x 10(-7) M, 2.5 x 10(-7) M, and 1.1 x 10(-7) M for CC, HP, DA and AM, respectively. EN was found not to have any significant effect on DNA synthesis. The results suggest that thymus gland atrophy, associated with use of CC may be related to the inhibition of thymocyte proliferation.

Naltrexone, naltrindole, and CTOP block cocaine-induced sensitization to seizures and death

I.c.v. injection for 9 days of either naltexone (NTX) (5, 10, 20, 40 micrograms/rat) or a selective mu peptide (CTOP) (0.125, 0.25, 0.5, 1, 3, 6 micrograms/rat) or delta (naltrindole) (NLT) (5, 10, 20 micrograms/rat) subtype opioid receptor antagonist affected sensitization to cocaine (COC) (50 mg/kg, i.p.) administered 10 min after. NTX (5 and 40 micrograms/rat), NLT (10 and 20 micrograms/rat), and the peptide CTOP (0.25-0.5 microgram/rat) attenuated seizure parameters (percent of animals showing seizures, mean score and latency) in a day-related manner. The DD50 (days to reach 50% of death) value for COC was 2.69, whereas it was 9.67 and 7.27 for NTX 5 and 40 micrograms/rat, 8.59 for NLT (10 micrograms/rat), and 6.11, 5.95, and 4.30 for CTOP (0.25, 0.5, and 1 microgram/rat respectively). These findings suggest a concurrent involvement of mu- and delta-opioid receptor subtype in COC-induced sensitization to toxic effects.

Effect of cocaine on macromolecular syntheses and cell proliferation in cultured glial cells

In the present study the effect of cocaine on thymidine, uridine and leucine incorporation was assessed in primary cortical glial and C6 glioma cells. Cocaine exposure for 24 h inhibited thymidine and uridine incorporation in cortical glial and C6 glioma cells. However, the effect of cocaine on uridine incorporation was less prominent compared to thymidine incorporation. High concentrations of cocaine inhibited leucine incorporation in C6 glioma cells but not in cortical glia. Cocaine exposure for four days decreased cell proliferation of cortical glial and C6 glioma cells. Cocaine-induced attenuation of macromolecular syntheses was not due to cell death since cocaine-treated cells were not stained with Trypan Blue and did not release lactate dehydrogenase into culture supernatants. Furthermore, cocaine had no effect on glutamate uptake either in cortical glia or in C6 glioma cells. These results indicate that cocaine inhibits macromolecular syntheses in glial cells. The inhibition of macromolecular syntheses in glial cells may be the mechanism involved in cocaine-induced fetal brain growth retardation.

Buprenorphine-cocaine interactions in mice: effect on locomotor activity and hole-dipping behaviour

The effect of cocaine and the mixed mu-opioid partial agonist/kappa-antagonist buprenorphine on locomotor activity and hole-dipping behaviour was investigated in mice. The drugs were given alone and in combination. Cocaine (7.5, 15, 30 mg kg-1, i.p.) significantly increased locomotion in a dose-related manner in the hour following injection. The two highest doses also increased hole-dipping although this response was not consistently seen. Buprenorphine (0.5, 5 mg kg-1, i.p.) produced an increase in locomotion which occurred 30-60 min after injection but did not alter hole-dipping behaviour. A lower dose (0.05 mg kg-1) had no effect on either parameter. The locomotion induced by cocaine (15 mg kg-1, i.p.) was not modified by buprenorphine (0.05, 0.5, 1, 5 mg kg-1, i.p.; 5 min pretreatment). However, hole-dipping was almost completely abolished in animals given combinations of cocaine and buprenorphine (0.05-5 mg kg-1, i.p.), although neither drug decreased hole-dipping when given alone. This observation, which was not simply due to the emergence of stereotyped behaviour, suggests an interaction between buprenorphine and cocaine.