The effect of repeat dosing with cimetidine on the pharmacokinetics of intravenous granisetron in healthy volunteers

Comparing the Therapeutic Effectiveness of N-acetylcysteine with the Combination of N-acetyl Cysteine and Cimetidine in Acute Acetaminophen Toxicity: A Double-Blinded Clinical Trial

BACKGROUND

N-acetylcysteine (NAC) has been used as a classic treatment for hepatotoxicity induced by N-acetyl-p-benzoquinone imine (NAPQI) as a metabolite of acetaminophen. However, cimetidine theoretically can reduce the production of toxic metabolites through the inhibition of cytochrome p450, and it recently was proposed as a complementary treatment for acetaminophen toxicity.

OBJECTIVE

The aim of this study was to compare the effects of treating acute acetaminophen toxicity with NAC alone and with a combination of NAC and cimetidine.

METHODS

From October 2013 to March 2014, 105 patients suspected of acetaminophen toxicity who had paraclinical confirmation of toxicity requiring medical treatment (based on the risk assessment nomogram of acetaminophen serum level) were enrolled in this double-blind, randomized, controlled trial at Imam Reza Hospital in Mashhad, Iran. The patients were divided into two groups, i.e., 1) patients who were treated with NAC alone (group A) and 2) patients who were treated with a combination of NAC and cimetidine (group B). The primary outcomes were 1) the serum level of acetaminophen and 2) the serum level of aminotransferases at the time of admission and 4, 12, 24, and 48 hours after admission. Exclusion criteria included multiple toxicities, concurrent diseases that could affect liver enzymes, the use of other drugs, and dissatisfaction with the project. For measuring quantitative data, SPSS version 16 was used for t-test analysis and for analyzing the qualitative data with chi-squared analysis.

RESULTS

Sixty patients (32 females and 28 males) with a mean age of 25.2 ± 7.3 years were classified in two groups of 30.. There was no difference between the groups in terms of their admission information. The average levels of acetaminophen in both groups at admission, 12, 24, and 48 hours after hospitalization were not significantly different from each other. Twelve hours after hospitalization, the aspartate aminotransferase (AST) level in the group treated with NAC was significantly higher than in the group treated with the combination of NAC and cimetidine (IU/L30.1 ± 110.0 versus IU/L26.38 ± 94.93, p = 0.044). At the other times that the level of liver enzymes was assessed, the serum levels of urea and creatinine were not significantly different in the two groups (p > 0.05).

CONCLUSION

The intravenous administration of 300 mg of cimetidine every six hours with NAC did not improve the level of hepatoprotective action significantly compared with the NAC treatment protocol alone.

Effects of Nigella sativa, Lepidium sativum and Trigonella foenum-graecum on sildenafil disposition in beagle dogs

The present study was conducted to investigate the effects of some commonly used herbs namely Nigella sativa, Lepidium sativum and Trigonella foenum-graecum on the pharmacokinetics of sildenafil in beagle dogs. The study design involved four treatments in a non-balanced crossover design. Sildenafil was given one tablet 100 mg orally to each dog and blood samples were obtained. After a suitable washout period, animals were commenced on a specific herb treatment for 1 week. Blood samples were withdrawn at different time intervals and sildenafil was analyzed by HPLC method. Oral administration of Nigella sativa resulted in reduction of AUC0-∞, C max and t 1/2 as compared to the control. Treatment of Lepidium sativum resulted in a significant reduction in the C max and AUC. There were no significant differences between the rests of the pharmacokinetic parameters relative to those of the control. For Trigonella foenum-graecum, the effects were similar to those obtained in case of Lepidium sativum. It was concluded that concurrent use of investigated herbs alters the pharmacokinetics of sildenafil. Co-administration of investigated herbs should be cautious since their concomitant use might result in decrease in sildenafil bioavailability.

[Maximal initial dose of simvastatin causing acute renal failure through rhabdomyolysis: risk factors, pathomechanism and therapy related to a case]

Rhabdomyolysis (RML) is a rare and severe adverse effect of simvastatin (SIM). Several risk factors have been described which play a role in its pathogenesis, namely age >65, diabetes mellitus, renal disease, high-dose statin therapy, chemicals metabolized by cytochrome P450 3A4 or idiosyncrasy.

CASE SUMMARY

A 66-year-old man with diabetes, ischaemic heart disease and hypertension, on medication of CYP3A4 substrates amlodipine and alprazolam, maximal daily dose of SIM has been started for unknown cholesterol level. On the second day dark-brown urine, paraparesis, bile-like vomiting, on his fourth day of treatment total tetraparesis and oliguria characterized RML with acute renal failure. During his hospitalization of one-hundred-six days he underwent fourty-nine dialysis treatments. Sixteen months follow-up after discharge from hospital, his walking improved up to using one stick now. His cholesterol level is in physiological range with no statin therapy.

CONCLUSIONS

On account of risk factors listed above this case should have been administered to low initial dose of SIM. Developing myalgia or weakness in muscles, treatment must be stopped. In a case of predisposition to RML statin therapy and dosage can only be performed under continuous supervision.

Drug-induced changes in P450 enzyme expression at the gene expression level: a new dimension to the analysis of drug-drug interactions

Drug-drug interactions (DDIs) caused by direct chemical inhibition of key drug-metabolizing cytochrome P450 enzymes by a co-administered drug have been well documented and well understood. However, many other well-documented DDIs cannot be so readily explained. Recent investigations into drug and other xenobiotic-mediated expression changes of P450 genes have broadened our understanding of drug metabolism and DDI. In order to gain additional information on DDI, we have integrated existing information on drugs that are substrates, inhibitors, or inducers of important drug-metabolizing P450s with new data on drug-mediated expression changes of the same set of cytochrome P450s from a large-scale microarray gene expression database of drug-treated rat tissues. Existing information on substrates and inhibitors has been updated and reorganized into drug-cytochrome P450 matrices in order to facilitate comparative analysis of new information on inducers and suppressors. When examined at the gene expression level, a total of 119 currently marketed drugs from 265 examined were found to be cytochrome P450 inducers, and 83 were found to be suppressors. The value of this new information is illustrated with a more detailed examination of the DDI between PPARalpha agonists and HMG-CoA reductase inhibitors. This paper proposes that the well-documented, but poorly understood, increase in incidence of rhabdomyolysis when a PPARalpha agonist is co-administered with a HMG-CoA reductase inhibitor is at least in part the result of PPARalpha-induced general suppression of drug metabolism enzymes in liver. The authors believe this type of information will provide insights to other poorly understood DDI questions and stimulate further laboratory and clinical investigations on xenobiotic-mediated induction and suppression of drug metabolism.

Same Old Story? Do We Need to Modify Our Supportive Care Treatment of Elderly Cancer Patients? Focus on Antiemetics

The incidence of cancer is highest among individuals > or =65 years of age. Physiological changes associated with aging, such as cognitive decline, renal and hepatic dysfunction, can often complicate treatment options, and the elderly represent a particular challenge to the oncologist because of the high incidence of comorbidity and polypharmacy. Effective supportive care is of particular importance in elderly cancer patients as they may recover less satisfactorily if adverse events are poorly controlled. Nevertheless, evidence suggests that supportive care agents, for example, antiemetics, are underutilised in this patient population. Chemotherapy and radiotherapy regimens are frequently associated with nausea and vomiting--symptoms that can have deleterious effects on vulnerable patients if not adequately managed. The serotonin 5-HT3-receptor antagonists represent a class of antiemetics that are currently regarded as the gold standard treatment for chemotherapy- and radiotherapy-induced nausea and vomiting. They are recommended as first-line treatment for patients at moderate-to-high risk of emesis. However, antiemetic guidelines do not differentiate between these agents and, more importantly, do not contain specific recommendations for the elderly. Pharmacological differences exist between the commonly available 5-HT3-receptor antagonists (dolasetron, granisetron, ondansetron, tropisetron and palonosetron), namely receptor sensitivity, duration of action, metabolism and tolerability profile. Of particular concern with prescriptions to elderly cancer patients is the convenience of once-daily administration, the low potential for drug-drug interactions and cardiovascular adverse effect profile. Moreover, the addition of the newly approved neurokinin NK1-receptor antagonist aprepitant to the choice of antiemetic regimen may complicate therapy and exacerbate the drug-drug interaction risk in elderly patients. Therefore, the use of antiemetics that are well tolerated and with the lowest risk of drug-drug interactions is imperative in this patient population and will enable even those patients with several comorbidities and a high level of polypharmacy to receive effective antiemetic therapy.