Plasma chlorpropamide: a critical factor in chlorpropamide-alcohol flush

Facial skin temperature in chlorpropamide alcohol flush

Objective methods to study the chlorpropamide alcohol flush (CPAF) have been inadequate. Determination of blood acetaldehyde has proved to be a promising method, but the analysis is difficult and time-consuming. To measure the facial skin temperature is more handy. The results of these measurements can be presented as delta T (skin temperature increase), %T (per cent of maximum possible temperature rise) or delta MTCI (malar thermal circulation index) after calculations. The baseline skin temperature is accounted for in %T and delta MTCI. Blood acetaldehyde determinations and placebo-alcohol tests can be used to separate the CPAF reaction from alcohol flushing. Single dose CPAF tests including facial skin temperature measurements were performed in 133 type 2 (non-insulin dependent) diabetics. Facial flush was observed in 42.9%. The specificity and sensitivity of all three skin temperature methods were high: 88.2, 85.5, 96.1%, and 89.5, 86.0, 86.0%, respectively. Skin temperature measurement, whether expressed as delta T, %T or delta MTCI, provides a method to study CPAF with high accuracy.

Comparative tolerability of sulphonylureas in diabetes mellitus

The sulphonylurea drugs have been the mainstay of oral treatment for patients with diabetes mellitus since they were introduced. In general, they are well tolerated, with a low incidence of adverse effects, although there are some differences between the drugs in the incidence of hypoglycaemia. Over the years, the drugs causing the most problems with hypoglycaemia have been chlorpropamide and glibenclamide (glyburide), although this is a potential problem with all sulphonylureas because of their action on the pancreatic beta cell, stimulating insulin release. Other specific problems have been reported with chlorpropamide that occur only rarely, if at all, with other sulphonylureas. Hyponatraemia secondary to inappropriate antidiuretic hormone activity, and increased flushing following the ingestion of alcohol, have been well described. The progressive beta cell failure with time results in eventual loss of efficacy, as these agents depend on a functioning beta cell and are ineffective in the absence of insulin-producing capacity. Differences in this secondary failure rate have been reported, with chlorpropamide and gliclazide having lower failure rates than glibenclamide or glipizide. The reasons for this are unclear, but the more abnormal pattern of insulin release produced by glibenclamide may be partly responsible and, indeed, may explain the increased risk of hypoglycaemia with this agent. Previously reported increased mortality associated with tolbutamide therapy has not been substantiated, and more recent data have shown no increased mortality from sulphonylurea treatment. Indeed, benefit from glycaemic control, regardless of the agent used--insulin or sulphonylurea--was reported by the United Kingdom Prospective Diabetes Study. Nevertheless, there is still ongoing controversy in view of the experimental evidence, mainly from animal studies, of potential adverse effects on the heart from sulphonylureas, but these are difficult to extrapolate into clinical situations. Most of these studies have been carried out with glibenclamide, which makes comparison of possible risk difficult. Other cardiovascular risk factors may be modified by gliclazide, which seems unique among the sulphonylureas in this respect. Its reported haemobiological and free radical scavenging activity probably resides in the azabicyclo-octyl ring structure in the side chain. Reduced progression or improvement in retinopathy has been reported in comparative trials with other sulphonylureas, and the effect is unrelated to improvements in glycaemia. There are differences between the sulphonylureas in some adverse effects, risk of hypoglycaemia, failure rates and actions on vascular risk factors. As a group of drugs, they are very well tolerated, but differences in overall tolerability can be identified.

Oral antidiabetic drug use in the elderly

Non-insulin-dependent diabetes mellitus (NIDDM) is a metabolic disease that is common in the elderly, and is characterised by insulin insufficiency and resistance. Measures such as bodyweight reduction and exercise improve the metabolic defects, but pharmacological therapy is the most frequently used and successful therapy. The sulphonylureas stimulate insulin secretion. Metformin and troglitazone increase glucose disposal and decrease hepatic glucose output without causing hypoglycaemia. Acarbose is a dietary aid that spreads the dietary carbohydrate challenge to endogenous insulin over time. These pharmacological agents, either alone or in combination, should improve blood glucose regulation in patients with NIDDM.

Alcohol and drug interactions

Interactions of ethyl alcohol with various drugs are common. Their consequences vary depending on the effects of the drugs concerned, the doses of drugs and alcohol given and their mode of administration. Pharmacokinetic interactions refer to altered tissue concentrations of alcohol or drugs or both and their metabolites which sometimes lead to serious toxic reactions. The kinetic interactions take place in the absorption or metabolism of alcohol or the drug, whereas significant interactions in their distribution phase are rare. Pharmacodynamic interactions refer to the combined actions, even serious ones, which primarily take place at the tissue (receptor?) level, with or without an important pharmacokinetic component of interaction. Acute substantial doses of alcohol given quickly tend to inhibit microsomal drug metabolism and thus enhance the effects of drugs. Chronic administration of alcohol usually induces the synthesis of cytochrome P-450 isoenzyme P-450 II E1, thus accelerating the metabolism of its own and, depending on the circumstances, of various drugs as well. Reduced actions of the agents may then ensue. If the (toxic) effect of a drug (e.g., paracetamol) depends on the formation of active metabolites acute intake of alcohol may, paradoxically, reduce the drug effect, while chronic alcohol intake enhances it. Induction of hepatic enzymes by alcohol may affect the turnover of endogenous vitamins and hormones, or even produce carcinogenic substances.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between the pharmacokinetics and pharmacodynamic effects of oral hypoglycaemic drugs

Oral hypoglycaemic drugs have widely differing pharmacokinetic properties. Possible pharmacodynamic benefits include greater efficacy and fewer adverse effects. In general, it has not been possible to demonstrate unequivocal differences in clinical efficacy between the sulphonylureas during long term use, although there are clear differences in potency. These differences have been emphasised to the extent that the term 'second-generation' has been used for the most potent sulphonylureas, but there is little to suggest that potency is of any therapeutic significance. Trials to study differences in efficacy have rarely been of acceptable design. They have often used fixed doses of drugs, begging the question of whether true potency ratios have been established for chronic treatment. They have rarely involved substantial numbers of patients in double-blind crossover studies with a suitable washout period. Trials which show that there is a clear relationship between drug concentrations in blood and drug effects (whether therapeutic effects or adverse effects such as severe hypoglycaemia) are generally lacking. Qualitative and semiquantitative analysis of adverse effects supports the concept that drugs with a long half-life (e.g. chlorpropamide), renally excreted active metabolites (e.g. acetohexamide) or unusual properties (e.g. glibenclamide, which accumulates progressively in islet tissue) are more likely to cause prolonged hypoglycaemia, which may be fatal. The major adverse effect of treatment with biguanides is lactic acidosis, and this probably occurs more commonly in patients treated with phenformin than those treated with metformin because of pharmacogenetic variation in phenformin metabolism. The available evidence therefore favours the use of drugs with a short elimination half-life which are extensively metabolised and which have no active metabolites.

Roles of chlorpropamide, alcohol and acetaldehyde in determining the chlorpropamide-alcohol flush

The value and reproducibility of the chlorpropamide-alcohol flush (CPAF) have been questioned, and objective measures of the test are required. Recording of facial skin temperature, measurement of chlorpropamide, ethanol and acetaldehyde concentrations have been proposed for this purpose. The present study was designed to evaluate the relative contributions of these variables in determining CPAF. Twenty-one Type 2 (non-insulin-dependent) diabetic patients (11 CPAF-positive and 10 CPAF-negative according to previous tests with standard amounts of alcohol and chlorpropamide) were investigated in a random fashion with either chlorpropamide or placebo given on three subsequent evenings before a two-step alcohol challenge with increasing body-weight-matched amounts of alcohol. Higher rises in facial skin temperature and heart rate, higher flush-score and higher acetaldehyde levels resulted from chlorpropamide therapy than followed placebo. After smaller alcohol challenges (with chlorpropamide pretreatment) there were positive intercorrelations between flush-score, rise in facial skin temperature, and plasma concentrations of chlorpropamide and blood acetaldehyde. The increased alcohol dose abolished most of these correlations and a minimum temperature rise of 1.8 degrees C appeared in all but two subjects regardless of previous CPAF classification. During the current experimental conditions, the previously-classified CPAF-positive and CPAF-negative patients did not differ with respect to flush-score, rise in skin temperature, heart rate, blood acetaldehyde or ethanol concentrations, whereas they differed with respect to chlorpropamide concentrations. The present results support the view that CPAF is associated with elevated blood acetaldehyde levels due to inhibition of aldehyde dehydrogenase by chlorpropamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlorpropamide-alcohol flush: significance of body weight, sex and serum chlorpropamide level

Chlorpropamide-alcohol flush (CPAF) tests were carried out in 15 male and 15 female Type 2 diabetics. Twelve subjects were CPAF-positive and 18 were -negative. The two groups did not differ in age or duration of diabetes, but the CPAF-positive subjects weighed less (mean difference 13 kg) and had higher plasma chlorpropamide levels. There was a negative correlation between plasma chlorpropamide and body weight, and a positive correlation between plasma chlorpropamide and the increase in facial skin temperature. Females had higher plasma chlorpropamide, a greater skin temperature increase and lower body weight than males; there were 11 females and only 1 male amongst the 12 CPAF-positive subjects. The findings confirm that plasma chlorpropamide is a major determinant of the CPAF reaction and also show that body weight strongly influences the chlorpropamide level and, consequently, the outcome of the CPAF test. The sex difference in body weight probably accounts for most, if not all, of the sex difference in the incidence of the CPAF.