Adverse events with concomitant use of simvastatin or atorvastatin and thiazolidinediones

Caffeine modulates pharmacokinetic and pharmacodynamic profiles of pioglitazone in diabetic rats: Impact on therapeutics

OBJECTIVES

To determine the influence of caffeine on pharmacokinetics and pharmacodynamics of pioglitazone (PIO) in diabetic rats.

METHODS

This was a preclinical study conducted in the College of Pharmacy, Najran University, Saudi Arabia, using 5 groups of Wistar rats: normal rats, untreated diabetic rats, diabetic rats + caffeine (20 mg/kg), diabetic rats + PIO (10 mg/kg), and diabetic rats + PIO (10 mg/kg) + caffeine (20 mg/kg). The drugs were administered for 14 days, and fasting plasma glucose concentrations were determined on the first day, and thereafter at weekly intervals. On day 14, rat sacrifice was followed with assay of levels of biomarkers. To estimate the pharmacokinetic parameters, the diabetic animals were assigned to 2 groups: one group received PIO (10 mg/kg), while the other received PIO + caffeine (20 mg/kg). Blood samples were drawn from the retro-orbital plexus at different time intervals, and pharmacokinetic parameters were measured using high performance liquid chromatography.

RESULTS

Caffeine caused statistically marked increases in area under the curve, Cmax, Tmax, and half-life of PIO, and decreased clearance. Combination of PIO and caffeine produced a synergistic effect on percentage reduction in blood glucose, with 67.1% reductions observed on day 7 and 68.9% reductions observed on day 14. Liver and cardiac biomarkers were significantly decreased, suggesting cardioprotective and hepatoprotective effects.

CONCLUSION

Co-administration of PIO with caffeine enhances its antidiabetic effect, probably due to enhanced bioavailability of PIO, leading to clinical benefits in diabetic patients.

Pioglitazone ameliorates retinal ischemia/reperfusion injury via suppressing NLRP3 inflammasome activities

AIM

To explore the role of Pioglitazone (Pio) on a mouse model of retinal ischemia/reperfusion (I/R) injury and to elucidate the potential mechanism.

METHODS

Retinal ischemia was induced in mice by increasing the intraocular pressure, and Pio was administered 4h though periocular injection before I/R. The number of cells in the ganglion cell layer (GCL) was counted 7d after retinal I/R injury. Glial fibrillary acidic protein (GFAP), nuclear factor-kappa B (NF-κB), p38, phosphorylated-p38, PPAR-γ, interleukin-1β (IL-1β), Toll-like receptor 4 (TLR4), NLRP3, cleaved caspase-1, caspase-1 were determined by real-time polymerase chain reaction and Western blotting.

RESULTS

Pio promoted the survival of retinal cells in GCL following retinal I/R injury (P<0.05). Besides, retinal I/R injury stimulated the expression of GFAP and TLR4, which were partially reversed by Pio treatment (P<0.05). Retinal I/R injury-upregulated expression of NLRP3, cleaved caspase-1, IL-1β was attenuated after Pio treatment (P<0.05). Moreover, I/R injury induced activation of NF-κB and p38 were inhibited by Pio treatment (P<0.05).

CONCLUSION

Pio promotes retinal ganglion cells survival by suppressing I/R-induced activation of TLR4/NLRP3 inflammasomes via inhibiting NF-κB and p38 phosphorylation.

Mitochondrial dysfunction and delayed hepatotoxicity: another lesson from troglitazone

AIMS/HYPOTHESIS

Troglitazone was approved for treatment of type 2 diabetes mellitus, but by 2000 it had been removed from all world markets due to severe drug-induced liver injury. Even today, we still do not know how many patients sustained a long-term liver injury. No system is in place to acquire that knowledge. Regarding toxicity mechanisms, controversy persists as to which ones are class effects of thiazolidinediones (TZDs) and which are unique to troglitazone. This study aims to provide long-term outcome data and new insights on mechanisms of troglitazone-induced liver injury.

METHODS

This case series reports the liver injuries sustained by eleven type 2 diabetic patients treated with troglitazone between 1997 and 2000. Exhaustive review of medical records was performed for all patients. Long-term outcomes were available for all the non-fatal cases. A comprehensive literature review was also performed.

RESULTS

Long-term liver injury progressing to cirrhosis was identified in seven patients. All eleven cases had liver injury patterns consistent with troglitazone toxicity. Analysis of these cases and of the experimental troglitazone toxicity data points to mitochondrial toxicity as a central factor. The general clinical patterns of mitochondrial hepatotoxic events are reviewed, as are the implications for other members of the TZD family.

CONCLUSIONS/INTERPRETATION

This analysis enables the liver injury induced by troglitazone to be better understood. In future cases of delayed drug-induced liver injury that progresses after discontinuation, the possibility of mitochondrial toxicity should be considered. When appropriate, this can then be evaluated experimentally. Such proactive investigation may anticipate clinical risk before a large-scale therapeutic misadventure occurs. Drug-induced liver injury due to mitochondrial hepatotoxins may be less unpredictable than has previously been surmised.

Pharmacokinetic interactions with thiazolidinediones

Type 2 diabetes mellitus is a complex disease combining defects in insulin secretion and insulin action. New compounds called thiazolidinediones or glitazones have been developed for reducing insulin resistance. After the withdrawal of troglitazone because of liver toxicity, two compounds are currently used in clinical practice, rosiglitazone and pioglitazone. These compounds are generally used in combination with other pharmacological agents. Because they are metabolised via cytochrome P450 (CYP), glitazones are exposed to numerous pharmacokinetic interactions. CYP2C8 and CYP3A4 are the main isoenzymes catalysing biotransformation of pioglitazone (as with troglitazone), whereas rosiglitazone is metabolised by CYP2C9 and CYP2C8. For both rosiglitazone and pioglitazone, the most relevant interactions have been described in healthy volunteers with rifampicin (rifampin), which results in a significant decrease of area under the plasma concentration-time curve [AUC] (54-65% for rosiglitazone, p<0.001; 54% for pioglitazone, p<0.001), and with gemfibrozil, which results in a significant increase of AUC (130% for rosiglitazone, p<0.001; 220-240% for pioglitazone, p<0.001). The relevance of such drug-drug interactions in patients with type 2 diabetes remains to be evaluated. However, in the absence of clinical data, it is prudent to reduce the dosage of each glitazone by half in patients treated with gemfibrozil. Conversely, rosiglitazone and pioglitazone do not seem to significantly affect the pharmacokinetics of other compounds. Although some food components have also been shown to potentially interfere with drugs metabolised with the CYP system, no published study deals specifically with these possible CYP-mediated food-drug interactions with glitazones.

Safety of lovastatin/extended release niacin compared with lovastatin alone, atorvastatin alone, pravastatin alone, and simvastatin alone (from the United States Food and Drug Administration adverse event reporting system)

Recent national guidelines support combination drug therapy targeting multiple lipid abnormalities. Current drug labeling warns of an increased risk of adverse events with statin and niacin combinations. These recommendations have been based solely on case reports. We compared the rates of adverse event reports (AERs) received by the United States Food and Drug Administration (1999 to March 2005) associated with the combination of lovastatin/niacin-extended release (ER) with those of lovastatin or niacin-ER alone, and other commonly used statins. The following AERs were considered: events that were fatal, life-threatening, or resulted in hospitalization (serious AERs), hepatotoxicity (liver AERs), and rhabdomyolysis (rhabdomyolysis AERs). We also calculated the prevalence of concomitant niacin-ER therapy in statin-associated AERs. The rate of serious AERs associated with the combination lovastatin/niacin-ER was similar to that of lovastatin or niacin-ER alone, and significantly less than that of atorvastatin or simvastatin. Likewise, the rates of liver and rhabdomyolysis AERs associated with lovastatin/niacin-ER were similar to those of the other statins or niacin-ER alone and lower than those of simvastatin-associated rhabdomyolysis reports (p <0.01). Concomitant niacin-ER use in statin-associated AERs was rare (<or=1%). In conclusion, these findings do not support a clinically significant adverse drug interaction between niacin-ER and statins and should encourage the safe use of this combination in appropriate high-risk patients, as recommended by the national guidelines.

Impact of thiazolidenediones on serum lipoprotein levels

The thiazolidinediones, acting through peroxisome proliferator-activated receptor chi (PPARchi), affect multiple areas of metabolism. Of increasing importance is the recognition that these agents affect lipoprotein metabolism and cause changes in serum lipid and lipoprotein levels. All three thiazolidinediones, including troglitazone (which was withdrawn in the year 2000), rosiglitazone, and pioglitazone, tend to increase high-density lipoprotein (HDL) cholesterol, increase the size/decrease the density of low-density lipoprotein (LDL) particles, and raise the level of lipoprotein(a). In addition, troglitazone and pioglitazone, but not rosiglitazone, lower triglyceride levels modestly, thereby further contributing to increases in LDL and HDL size. The mechanism for these effects is still being clarified, but may involve enhancement of triglyceride clearance (in the case of pioglitazone), alteration of apolipoprotein C-III levels, reduction of hepatic lipase, and increase in ATP binding cassette A1 (ABCA1) activity. The clinical implications of these effects need further exploration.

Drug interactions of clinical importance with antihyperglycaemic agents: an update

Because management of type 2 diabetes mellitus usually involves combined pharmacological therapy to obtain adequate glucose control and treatment of concurrent pathologies (especially dyslipidaemia and arterial hypertension), drug-drug interactions must be carefully considered with antihyperglycaemic drugs. Additive glucose-lowering effects have been extensively reported when combining sulphonylureas (or the new insulin secretagogues, meglitinide derivatives, i.e. nateglinide and repaglinide) with metformin, sulphonylureas (or meglitinide derivatives) with thiazolidinediones (also called glitazones) and the biguanide compound metformin with thiazolidinediones. Interest in combining alpha-glucosidase inhibitors with either sulphonylureas (or meglitinide derivatives), metformin or thiazolidinediones has also been demonstrated. These combinations result in lower glycosylated haemoglobin (HbA(1c)), fasting glucose and postprandial glucose levels than with either monotherapy. Even if modest pharmacokinetic interferences have been reported with some combinations, they do not appear to have important clinical consequences. No significant adverse effects, except a higher risk of hypoglycaemic episodes that may be attributed to better glycaemic control, occur with any combination. Challenging the classical dual therapy with sulphonylurea plus metformin, there is a recent trend to use alternative dual combinations (sulphonylurea plus thiazolidinedione or metformin plus thiazolidinedione). In addition, triple therapy with the addition of a thiazolidinedione to the metformin-sulphonylurea combination has been recently evaluated and allows glucose targets to be reached before insulin therapy is considered. This triple therapy appears to be safe, with no deleterious drug-drug interactions being reported so far.Potential interferences may also occur between glucose-lowering agents and other drugs, and such drug-drug interactions may have important clinical implications. Relevant pharmacological agents are those that are widely coadministered in diabetic patients (e.g. lipid-lowering agents, antihypertensive agents); those that have a narrow efficacy/toxicity ratio (e.g. digoxin, warfarin); or those that are known to induce (rifampicin [rifampin]) or inhibit (fluconazole) the cytochrome P450 (CYP) system. Metformin is currently a key compound in the pharmacological management of type 2 diabetes, used either alone or in combination with other antihyperglycaemics. There are no clinically relevant metabolic interactions with metformin, because this compound is not metabolised and does not inhibit the metabolism of other drugs. In contrast, sulphonylureas, meglitinide derivatives and thiazolidinediones are extensively metabolised in the liver via the CYP system and thus, may be subject to drug-drug metabolic interactions. Many HMG-CoA reductase inhibitors (statins) are also metabolised via the CYP system. Even if modest pharmacokinetic interactions may occur, it is not clear whether drug-drug interactions between oral antihyperglycaemic agents and statins may have clinical consequences regarding both efficacy and safety. In contrast, a marked pharmacokinetic interference has been reported between gemfibrozil and repaglinide and, to a lesser extent, between gemfibrozil and rosiglitazone. This leads to a drastic increase in plasma concentrations of each antihyperglycaemic agent when they are coadministered with the fibric acid derivative, and an increased risk of adverse effects. Some antihypertensive agents may favour hypoglycaemic episodes when co-prescribed with sulphonylureas or meglitinide derivatives, especially ACE inhibitors, but this effect seems to result from a pharmacodynamic drug-drug interaction rather than from a pharmacokinetic drug-drug interaction. No, or only modest, interferences have been described with glucose-lowering agents and other pharmacological compounds such as digoxin or warfarin. The effects of inducers or inhibitors of CYP isoenzymes on the metabolism and pharmacokinetics of the glucose-lowering agents of each pharmacological class has been tested. Significantly increased (with CYP inhibitors) or decreased (with CYP inducers) plasma levels of sulphonylureas, meglitinide derivatives and thiazolidinediones have been reported in healthy volunteers, and these pharmacokinetic changes may lead to enhanced or reduced glucose-lowering action, and thus hypoglycaemia or worsening of metabolic control, respectively. In addition, some case reports have evidenced potential drug-drug interactions with various antihyperglycaemic agents that are usually associated with a higher risk of hypoglycaemia.

Treating insulin resistance in type 2 diabetes with metformin and thiazolidinediones

Insulin resistance underlies the pathogenesis of hyperglycaemia and cardiovascular disease in most people with type 2 diabetes. Metformin and thiazolidinediones (pioglitazone and rosiglitazone) counter insulin resistance by different cellular mechanisms and with complementary effects, making them suited for use in combination. Metformin exerts a stronger suppression of hepatic glucose output, while thiazolidinediones produce a greater increase in peripheral glucose uptake, enabling metformin-thiazolidinedione combinations to improve glycaemic control in type 2 diabetes with additive efficacy. Basal insulin concentrations are not raised by metformin or thiazolidinediones, so there is minimal risk of hypoglycaemia, and metformin can reduce the weight gain associated with thiazolidinediones. There are overlapping effects of metformin and thiazolidinediones against a range of athero-thrombotic factors and markers. These include decreased plasminogen activator inhibitor-1, reduced platelet aggregation, reductions of several vascular adhesion molecules, and reduced markers of low-grade inflammation such as C-reactive protein. Additionally, thiazolidinediones increase adiponectin and slightly reduce blood pressure. Both metformin and thiazolidinediones can improve components of the lipid profile: thiazolidinediones consistently reduce free fatty acid concentrations and decrease the proportion of small dense low-density-lipoprotein, and pioglitazone also decreases triglycerides. During co-administration, metformin and thiazolidinediones do not interfere with each other's pharmacokinetics, and lower doses of the two agents together can achieve efficacy with fewer side effects. Metformin-thiazolidinedione combinations require attention to the precautions for both agents, especially renal, cardiac and hepatic status. Thus, metformin and thiazolidinediones can be used in combination to address the hyperglycaemia and vascular risk in type 2 diabetes.