Propranolol disposition in renal failure

Antihypertensive treatment of end-stage renal disease patients on hemodialysis does not alter circulating ACE and ACE2 activity and angiotensin peptides

Cardiovascular diseases (CVD) are the main causes of death in hemodialysis patients, representing a public health challenge. We investigated the effect of different antihypertensive treatments on circulating levels of renin-angiotensin system (RAS) components in end-stage renal disease (ESRD) patients on hemodialysis. ESRD patients were grouped following the prescribed antihypertensive drugs: ß-blocker, ß-blocker+ACEi and ß-blocker+AT1R blocker. ESDR patients under no antihypertensive drug treatment were used as controls. Blood samples were collected before hemodialysis sessions. Enzymatic activities of the angiotensin-converting enzymes ACE and ACE2 were measured through fluorescence assays and plasma concentrations of the peptides Angiotensin II (Ang II) and Angiotensin-(1-7) [Ang-(1-7)] were quantified using mass spectrometry (LC-MS/MS). ACE activity was decreased only in the ß-blocker+ACEi group compared to the ß-blocker+AT1R, while ACE2 activity did not change according to the antihypertensive treatment. Both Ang II and Ang-(1-7) levels also did not change according to the antihypertensive treatment. We concluded that the treatment of ESRD patients on hemodialysis with different antihypertensive drugs do not alter the circulating levels of RAS components.

Extracorporeal treatment for poisoning to beta-adrenergic antagonists: systematic review and recommendations from the EXTRIP workgroup

BACKGROUND

β-adrenergic antagonists (BAAs) are used to treat cardiovascular disease such as ischemic heart disease, congestive heart failure, dysrhythmias, and hypertension. Poisoning from BAAs can lead to severe morbidity and mortality. We aimed to determine the utility of extracorporeal treatments (ECTRs) in BAAs poisoning.

METHODS

We conducted systematic reviews of the literature, screened studies, extracted data, and summarized findings following published EXTRIP methods.

RESULTS

A total of 76 studies (4 in vitro and 2 animal experiments, 1 pharmacokinetic simulation study, 37 pharmacokinetic studies on patients with end-stage kidney disease, and 32 case reports or case series) met inclusion criteria. Toxicokinetic or pharmacokinetic data were available on 334 patients (including 73 for atenolol, 54 for propranolol, and 17 for sotalol). For intermittent hemodialysis, atenolol, nadolol, practolol, and sotalol were assessed as dialyzable; acebutolol, bisoprolol, and metipranolol were assessed as moderately dialyzable; metoprolol and talinolol were considered slightly dialyzable; and betaxolol, carvedilol, labetalol, mepindolol, propranolol, and timolol were considered not dialyzable. Data were available for clinical analysis on 37 BAA poisoned patients (including 9 patients for atenolol, 9 for propranolol, and 9 for sotalol), and no reliable comparison between the ECTR cohort and historical controls treated with standard care alone could be performed. The EXTRIP workgroup recommends against using ECTR for patients severely poisoned with propranolol (strong recommendation, very low quality evidence). The workgroup offered no recommendation for ECTR in patients severely poisoned with atenolol or sotalol because of apparent balance of risks and benefits, except for impaired kidney function in which ECTR is suggested (weak recommendation, very low quality of evidence). Indications for ECTR in patients with impaired kidney function include refractory bradycardia and hypotension for atenolol or sotalol poisoning, and recurrent torsade de pointes for sotalol. Although other BAAs were considered dialyzable, clinical data were too limited to develop recommendations.

CONCLUSIONS

BAAs have different properties affecting their removal by ECTR. The EXTRIP workgroup assessed propranolol as non-dialyzable. Atenolol and sotalol were assessed as dialyzable in patients with kidney impairment, and the workgroup suggests ECTR in patients severely poisoned with these drugs when aforementioned indications are present.

Clinical Pharmacokinetics of Propranolol Hydrochloride: A Review

BACKGROUND

Nobel laureate Sir James Black's molecule, propranolol, still has broad potential in cardiovascular diseases, infantile haemangiomas and anxiety. A comprehensive and systematic review of the literature for the summarization of pharmacokinetic parameters would be effective to explore the new safe uses of propranolol in different scenarios, without exposing humans and using virtual-human modeling approaches.

OBJECTIVE

This review encompasses physicochemical properties, pharmacokinetics and drug-drug interaction data of propranolol collected from various studies.

METHODS

Clinical pharmacokinetic studies on propranolol were screened using Medline and Google Scholar databases. Eighty-three clinical trials, in which pharmacokinetic profiles and plasma time concentration were available after oral or IV administration, were included in the review.

RESULTS

The study depicts that propranolol is well absorbed after oral administration. It has dose-dependent bioavailability, and a 2-fold increase in dose results in a 2.5-fold increase in the area under the curve, a 1.3-fold increase in the time to reach maximum plasma concentration and finally, 2.2 and 1.8-fold increase in maximum plasma concentration in both immediate and long-acting formulations, respectively. Propranolol is a substrate of CYP2D6, CYP1A2 and CYP2C19, retaining potential pharmacokinetic interactions with co-administered drugs. Age, gender, race and ethnicity do not alter its pharmacokinetics. However, in renal and hepatic impairment, it needs a dose adjustment.

CONCLUSION

Physiochemical and pooled pharmacokinetic parameters of propranolol are beneficial to establish physiologically based pharmacokinetic modeling among the diseased population.

β-Blocker dialyzability and mortality in older patients receiving hemodialysis

Some β-blockers are efficiently removed from the circulation by hemodialysis ("high dialyzability") whereas others are not ("low dialyzability"). This characteristic may influence the effectiveness of the β-blockers among patients receiving long-term hemodialysis. To determine whether new use of a high-dialyzability β-blocker compared with a low-dialyzability β-blocker associates with a higher rate of mortality in patients older than age 66 years receiving long-term hemodialysis, we conducted a propensity-matched population-based retrospective cohort study using the linked healthcare databases of Ontario, Canada. The high-dialyzability group (n=3294) included patients initiating atenolol, acebutolol, or metoprolol. The low-dialyzability group (n=3294) included patients initiating bisoprolol or propranolol. Initiation of a high- versus low-dialyzability β-blocker was associated with a higher risk of death in the following 180 days (relative risk, 1.4; 95% confidence interval, 1.1 to 1.8; P<0.01). Supporting this finding, we repeated the primary analysis in a cohort of patients not receiving hemodialysis and found no significant association between dialyzability and the risk of death (relative risk, 1.0; 95% confidence interval, 0.9 to 1.3; P=0.71). β-Blocker exposure was not randomly allocated in this study, so a causal relationship between dialyzability and mortality cannot be determined. However, our findings should raise awareness of this potentially important drug characteristic and prompt further study.

The effect of chronic renal failure on drug metabolism and transport

BACKGROUND

Chronic renal failure (CRF) has been shown to significantly reduce the nonrenal clearance and alter bioavailability of drugs predominantly metabolized by the liver and intestine.

OBJECTIVES

The purpose of this article is to review all significant animal and clinical studies dealing with the effect of CRF on drug metabolism and transport.

METHODS

A search of the National Library of Medicine PubMed was done with terms such as chronic renal failure, cytochrome P450 [CYP], liver metabolism, efflux drug transport and uptake transport, including relevant articles back to 1969.

RESULTS

Animal studies in CRF have shown a significant downregulation (40-85%) of hepatic and intestinal CYP metabolism. High levels of parathyroid hormone, cytokines and uremic toxins have been shown to reduce CYP activity. Phase II reactions and drug transporters such as P-glycoprotein and organic anion transporting polypeptide are also affected.

CONCLUSION

CRF alters intestinal, renal and hepatic drug metabolism and transport producing a clinically significant impact on drug disposition and increasing the risk for adverse drug reactions.

Predictions of the In Vivo Clearance of Drugs from Rate of Loss Using Human Liver Microsomes for Phase I and Phase II Biotransformations

PURPOSE

The utility of in vitro metabolism to accurately predict the clearance of hepatically metabolized drugs was evaluated. Three major goals were: (1) to optimize substrate concentration for the accurate prediction of clearance by comparing to Km value, (2) to prove that clearance of drugs by both oxidation and glucuronidation may be predicted by this method, and (3) to determine the effects of nonspecific microsomal binding and plasma protein binding.

METHODS

The apparent Km values for five compounds along with scaled intrinsic clearances and predicted hepatic clearances for eight compounds were determined using a substrate loss method. Nonspecific binding to both plasma and microsomal matrices were also examined in the clearance calculations.

RESULTS

The Km values were well within the 2-fold variability expected for between laboratory comparisons. Using both phase I and/or phase II glucuronidation incubation conditions, the predictions of in vivo clearance using the substrate loss method were shown to correlate with published human clearance values. Of particular interest, for highly bound drugs (>95% plasma protein bound), the addition of a plasma protein binding term increased the accuracy of the prediction of in vivo clearance.

CONCLUSIONS

The substrate loss method may be used to accurately predict hepatic clearance of drugs.

Intestinal Absorption and Hepatic Extraction of Propranolol and Metoprolol in Rats with Bilateral Ureteral Ligation

To investigate the mechanism responsible for the increased bioavailability of propranolol in bilateral ureter-ligated (BUL) rats, the intestinal absorption and hepatic extraction of propranolol and metoprolol were evaluated. The initial absorption rate of these drugs after intra-intestinal administration was only slightly increased in the BUL rats, whereas the blood drug concentration in these rats was higher than that in control rats. The blood propranolol and metoprolol concentrations during intra-portal infusion in the BUL rat were significantly higher than that in the control rat. In the presence of NADPH, the intrinsic metabolic activity of metoprolol in hepatic microsomes was not altered by BUL. On the other hand, the NADPH generation rate in the hepatic cytosol in the BUL group was lower than that in the control group. These results indicate that the absorption rate-dependent decrease in hepatic first-pass clearance of propranolol and metoprolol due to saturation kinetics is marginal, and that the hepatic metabolic activity and extraction of the drugs is significantly decreased in BUL rats probably due to the reduced NADPH generation rate in the liver.

The effect of chronic renal failure on hepatic drug metabolism and drug disposition

There is abundant evidence that chronic renal failure (CRF) and end-stage renal disease (ESRD) alter drug disposition by affecting protein and tissue binding and reducing systemic clearance of renally cleared drugs. What is not fully appreciated is that CRF can significantly reduce nonrenal clearance and alter the bioavailability of drugs predominantly metabolized by the liver. Animal studies in CRF have shown a major down-regulation (40-85%) of hepatic cytochrome P-450 metabolism involving specific isozymes. Phase II reactions such as acetylation and glucuronidation are also involved, with some isozymes showing induction and others inhibition. Hepatic enzymes exhibiting genetic polymorphisms such as N-acetyl-transferase-2 (NAT-2), which is responsible for the rapid and slow acetylator phenotypes, have been shown to be inhibited by ESRD and reversed by transplantation. There is some evidence pointing to the possibility of inhibitory factors circulating in the serum in ESRD patients which may be dialyzable. This review includes all significant animal and clinical studies using the search terms "chronic renal failure,""cytochrome P-450," and "liver metabolism" over the past 10 years obtained from the National Library of Medicine MEDLINE database, including relevant articles back to 1969.

Individual variation in first-pass metabolism

Individual variation in pharmacokinetics has long been recognised. This variability is extremely pronounced in drugs that undergo extensive first-pass metabolism. Drug concentrations obtained from individuals given the same dose could range several-fold, even in young healthy volunteers. In addition to the liver, which is the major organ for drug and xenobiotic metabolism, the gut and the lung can contribute significantly to variability in first-pass metabolism. Unfortunately, the contributions of the latter 2 organs are difficult to quantify because conventional in vivo methods for quantifying first-pass metabolism are not sufficiently specific. Drugs that are mainly eliminated by phase II metabolism (e.g. estrogens and progestogens, morphine, etc.) undergo significant first-pass gut metabolism. This is because the gut is rich in conjugating enzymes. The role of the lung in first-pass metabolism is not clear, although it is quite avid in binding basic drugs such as lidocaine (lignocaine), propranolol, etc. Factors such as age, gender, disease states, enzyme induction and inhibition, genetic polymorphism and food effects have been implicated in causing variability in pharmacokinetics of drugs that undergo extensive first-pass metabolism. Of various factors considered, age and gender make the least evident contributions, whereas genetic polymorphism, enzymatic changes due to induction or inhibition, and the effects of food are major contributors to the variability in first-pass metabolism. These factors can easily cause several-fold variations. Polymorphic disposition of imipramine and propafenone, an increase in verapamil first-pass metabolism by rifampicin (rifampin), and the effects of food on propranolol, metoprolol and propafenone, are typical examples. Unfortunately, the contributions of these factors towards variability are unpredictable and tend to be drug-dependent. A change in steady-state clearance of a drug can sometimes be exacerbated when first-pass metabolism and systemic clearance of a drug are simultaneously altered. Therefore, an understanding of the source of variability is the key to the optimisation of therapy.

The effect of renal failure on hepatic drug clearance

It is known that loss of renal function decreases the hepatic clearance of some drugs, but the mechanisms by which this occurs are unclear. Knowledge of which drugs display reduced hepatic metabolism may be important for appropriate dosing of these drugs in uremic patients. Although no firm conclusions can be made regarding common pharmacokinetic and metabolic characteristics of drugs that display decreased hepatic metabolism in renal failure, certain observations deserve consideration. It appears that drugs metabolized by oxidation, conjugation, or both may be predisposed to decreased hepatic clearance in renal failure. Drugs that undergo oxidation by the P-450IID6 isozyme may be more likely to exhibit inhibition whereas those metabolized by the P-450IIIA4 isozyme may be spared. Future studies designed to clarify the mechanisms of decreased hepatic clearance in renal failure should take into account the multiplicity of P-450 enzymes for drugs that are oxidatively metabolized. The phenomenon of reduced hepatic drug clearance in uremia should be considered when evaluating the influence of renal failure on drug disposition.

Antihypertensive therapy in the aged patient. Clinical pharmacokinetic considerations

The incidence of both systolic and diastolic hypertension is increased in elderly patients, therefore antihypertensive drugs are commonly used in this population. In addition to changes in blood pressure, the aging process also causes numerous changes in other physiological parameters, resulting in altered pharmacokinetic and pharmacodynamic responses to the drugs. The dosage regimens for thiazide diuretics and amiloride must be individually titrated in the elderly patient, since the elimination of these agents decreases concurrently with decreased renal function, as indicated by compromised creatinine clearance. The initial doses of the calcium antagonists should be decreased in elderly patients, since representative compounds from all 3 chemically heterogeneous classes have been shown to have decreased clearance in these patients which appears to be primarily due to the status of hepatic function in the patient. However, with verapamil, the dosage should be further decreased in association with compromised renal function. The dosage of the angiotensin converting enzyme (ACE) inhibitors should be adjusted according to renal function rather than age. Lisinopril, which is primarily eliminated unchanged, is usually given in lower doses in the elderly, and doses of both captopril and enalapril may need to be reduced, depending on renal function. While there is no need to adjust the dosage regimen for the alpha-adrenoceptor blocking drugs (prazosin, terazosin), caution should be used with the beta-adrenergic blockers, particularly the hydrophilic agents, since they are renally eliminated. Labetalol may be a suitable alternative beta-blocker for the elderly patient, since its pharmacodynamic properties of decreased systemic vascular resistance without changes in heart rate or stroke volume are preferential for the elderly patient, and its pharmacokinetics are relatively unchanged in this population. Drugs that act primarily through the central nervous system, such as clonidine, methyldopa and guanfacine, require smaller doses in the presence of renal dysfunction. In contrast, guanabenz is metabolised primarily by the liver, so it would appear to be useful in elderly patients with renal dysfunction despite the lack of studies in this population. Guanadrel, an adrenergic neuron blocking drug, also requires a dosage reduction in patients with impaired renal function. In addition to the pharmacokinetic changes that occur in the elderly patient, pharmacodynamic changes may also be anticipated due to receptor modifications. Older patients have a decrease in beta-receptor sensitivity, while alpha-receptor sensitivity does not change. When designing the dosage regimen for a senior patient with hypertension, the combination of all these variables must be considered.

Disease-induced variations in plasma protein levels. Implications for drug dosage regimens (Part II)

Part I of this article, which appeared in the previous issue of the Journal, discussed the implications of variations in plasma protein levels in a number of diseases: hepatic and renal disease, acute myocardial infarction, burns, cancer, diabetes mellitus, hyperlipidaemia and inflammatory diseases. In Part II the authors continue their review with a further range of disease states, and consider their import for drug dosages.

Clinical pharmacokinetic considerations in the elderly. An update

There are numerous studies of drug handling in the elderly, but it is difficult to assess the significance of changes seen in vitro, or after single-dose administration, because they are often compensated by other mechanisms at steady-state. However, a knowledge of these studies is important as the results alert the investigator to possible treatment problems. The high incidence of adverse drug reaction in the elderly population leaves no doubt that improvements in therapy are needed. Research has been directed at seeking patterns of abnormality in the elderly on which to base recommendations for alterations in dosage regimens. The major shortcoming of this approach has been the failure to distinguish between the effect of chronological age on drug pharmacokinetics, and drug kinetics in elderly people with multiple pathology. The latter concern appreciates the variety of factors involved and the importance of treating each patient as an individual: presentation of mean data is confusing and misleading. The objective of drug treatment in any age group, but particularly in the elderly, is to administer the smallest possible dose which gives adequate therapeutic benefit throughout the entire dosage interval with the minimum of side effects. For most drugs the safe starting dose in the elderly is one-third to half that recommended in the young. Vigilance for potential side effects with plasma concentration monitoring, if available, should help keep toxicity to a minimum. When other medications are added or changed, the possibility of interaction should be anticipated. Methods for individualisation of dosage regimens and the use of sustained-release formulations in the elderly are discussed. Dosage alteration in the elderly in terms of reduced dose frequency, rather than dose size, may help improve compliance. A knowledge of the pharmacokinetics of a drug helps determine which approach will be most beneficial.

Clinical pharmacokinetics in organ transplant patients

Diseases of the liver, kidney and heart influence the pharmacokinetics of several drugs. Organ transplantation is an accepted therapeutic option for the treatment of several disease states associated with these organs. Recently, there has been an increase in both graft and patient survival after transplantation of the liver, heart, kidney and bone marrow. Such patients normally receive a wide range of drugs, and optimisation of drug therapy requires a thorough understanding of the pharmacokinetics and pharmacodynamics of these drugs in transplant patients. However, only limited studies have been carried out to characterise drug kinetics in these situations. Available information indicates that drug kinetics cannot be considered normal in transplant patients. Drug absorption generally appears to be similar to that in healthy subjects. The plasma protein binding of drugs that primarily bind to albumin increases after transplantation, but remains lower than that observed in healthy subjects. While the binding of certain basic drugs may increase after transplantation due to an increase in the concentration of alpha 1-acid glycoprotein, a lower albumin concentration may mask this effect. Oxidative and conjugative metabolism as measured by the kinetics of antipyrine (phenazone) and paracetamol (acetaminophen) is normal, while the metabolism of steroids may be impaired. Serum creatinine does not appear to be a good indicator of the functional status of the kidney in transplant patients. It is also important to realise that there will be time-dependent changes in several kinetic parameters of drugs due to improvement in the physiological function from that associated with the disease state to that of the normal state. Individualisation and close monitoring of drug therapy is necessary in transplant patients.

Clinical pharmacokinetics of beta-adrenoceptor antagonists. An update

The beta-adrenoceptor antagonists have been widely used clinically for over 20 years and their pharmacokinetics have been more thoroughly investigated than any other group of drugs. Their various lipid solubilities are associated with differences in absorption, distribution and excretion. All are adequately absorbed, and some like atenolol, sotalol and nadolol which are poorly lipid-soluble are excreted unchanged in the urine, accumulating in renal failure but cleared normally in liver disease. The more lipid-soluble drugs are subject to variable metabolism in the liver, which may be influenced by age, phenotype, environment, disease and other drugs, leading to more variable plasma concentrations. Their clearance is reduced in liver disease but is generally unchanged in renal dysfunction. All the beta-adrenoceptor antagonists reduce cardiac output and this may reduce hepatic clearance of highly extracted drugs. In addition, the metabolised drugs compete with other drugs for enzymatic biotransformation and the potential for interaction is great, but because of the high therapeutic index of beta-adrenoceptor antagonists, any unexpected clinical effects are more likely to be due to changes in the kinetics of the other drug. Because satisfactory plasma concentration effect relationships have been difficult to establish for most clinical indications, and little dose-related toxicity is seen, plasma beta-adrenoceptor antagonist concentration measurement is usually unnecessary. The investigation of the clinical pharmacokinetics of the beta-adrenoceptor antagonists has added greatly to our theoretical and practical knowledge of pharmacokinetics and made some contribution to their better clinical use.

Renal disease and drug metabolism: an overview

Renal disease will perturb the disposition of drugs that primarily depend upon renal excretory function for elimination. While changes in drug half-life (T1/2) are often cited as evidence of altered drug disposition, it must be remembered that T1/2 is a dependent variable whose magnitude varies directly with volume of distribution (Vd) and indirectly with total body clearance (ClT). ClT is the one term that succinctly describes drug elimination. ClT is defined as the sum of the renal (ClR) and nonrenal (ClNR), or metabolic, clearances of a drug. Renal failure has been shown to alter the hepatic microsomal mixed-function oxidase system of drug metabolizing enzymes. Therefore, in end-stage renal failure, the potential exists for the modification of the disposition of drugs whose elimination is primarily hepatic. The kidneys themselves contain many of the enzymes important in hepatic drug metabolism. Drugs such as morphine, paracetamol, and p-aminobenzoic acid are metabolized in the kidney and experimental renal disease has been shown to reduce drug metabolism in the diseased kidney compared with the contralateral normal kidney. Renal disease, then, has the potential to alter not only the renal clearance of unchanged drug but also may substantially modify the metabolic transformation of drugs in both the liver and the kidneys. It can no longer be assumed that the pharmacokinetics of drugs that are disposed mainly by metabolism will be unaltered in renal failure.

Nadolol in hypertensive patients maintained on long-term hemodialysis

The pharmacokinetics, efficacy, and safety of nadolol were evaluated in hypertensive patients maintained on long-term hemodialysis. In nine patients the plasma elimination half-life of unchanged nadolol averaged 26 hours following a single 40 mg oral dose during the interdialytic period. Nineteen patients received nadolol once after each dialysis session. In addition, 12 of the 19 patients also received hydralazine and/or furosemide daily. Predialysis blood pressures and heart rates were significantly lower with nadolol than with combination or single therapy with conventional antihypertensive drugs, including other beta blockers. Nadolol administered only after each dialysis session (i.e., two or three times a week), in conjunction with hydralazine and/or furosemide, is an effective antihypertensive agent in hypertensive patients receiving long-term hemodialysis.

Pharmacokinetics of l-propranolol during repetitive dosing in normal and uranyl nitrate-induced renal failure rats

The effect of experimental renal failure on the intravenous and oral pharmacokinetics of l-propranolol was studied in rats. Renal failure was induced by a single intravenous injection of uranyl nitrate (5 mg/kg). Pharmacokinetic studies were carried out on the fifth day after injection of the renal toxin (renal failure group) or saline (control group). Serum concentration time course of l-propranolol was characterized after a single intravenous or oral dose as well as after five consecutive doses of the drug given at 3-hr intervals. During repetitive intravenous drug administration, steady state was reached by the second dose, i.e., within 6 hr after initiation of repetitive dosing. No significant difference in the serum concentration time course of l-propranolol was observed between control and renal failure animals. In both groups the AUC over the steady-state dosing interval was on the average 21-27% higher than the AUC after a single dose, indicating a slight decrease in the systemic clearance of l-propranolol during repetitive intravenous drug administration. An approximately two- to three-fold higher serum l-propranolol concentration was observed in renal failure animals as compared to the normal controls after both single or repetitive oral dosing. The apparent reduction in oral clearance probably reflected an inhibition of the hepatic first-pass metabolism of l-propranolol in the renal failure rat. An unexpectedly high and protracted accumulation of serum l-propranolol concentration was observed during repetitive oral drug administration. Continuing accumulation was still evident after the fifth oral dose, i.e., a period of 15 hr or approximately 10 half-lives. The mean AUC over the last dosing interval was 32.0 and 17.8 times higher than the predicted steady-state estimate based on single oral dose data for control and renal failure rats, respectively. The substantial reduction in the oral clearance during repetitive drug administration may be due to an auto-inhibition of l-propranolol metabolism.

Alteration of drug-protein binding in renal disease

The protein binding of acidic drugs but not basic drugs is decreased in serum from patients with poor renal function. This decreased binding is due to the retention of compounds that displace drugs from their binding sites on albumin. Phenytoin and valproic acid are the 2 drugs that require a change in the values for therapeutic levels to allow for this decreased binding.

Pharmacokinetics of mepindolol in patients with chronic renal failure

Five patients with a creatinine clearance of 14 to 37 ml/min/1.73 m2 were each given an oral dose of 10 mg of the beta-blocker mepindolol sulphate (Corindolan). In addition, two dialysis patients received the same dose either during hemodialysis or on a dialysis-free day. Plasma levels of mepindolol were measured by a sensitive, specific HPLC method. Mepindolol was rapidly absorbed in all the patients. The maximum plasma level of 35 +/- 8 ng/ml was reached after 1.4 +/- 0.5 h. The half-life of disposition was 4.0 +/- 1.5 h. The area under the plasma concentration-time curve was 237 +/- 84 ng X h/ml. The data obtained were no different from those found in normal healthy volunteers.

Drug therapy in patients undergoing haemodialysis. Clinical pharmacokinetic considerations

Haemodialysis is utilised therapeutically as supportive treatment for end-stage renal disease (ESRD). In conjunction with haemodialysis therapy, ESRD patients frequently receive a large number of drugs to treat a multitude of intercurrent conditions. Because of the impaired renal function in ESRD patients, dosage reduction is often recommended to avoid adverse drug reactions, particularly for drugs and active metabolites with extensive renal excretion. On the other hand, if the removal of a drug by haemodialysis during concomitant drug therapy is significant, a dosage supplement would be required to ensure adequate therapeutic efficacy. Knowledge of the impact of haemodialysis on the elimination of specific drugs is therefore essential to the rational design of the dosage regimen in patients undergoing haemodialysis. This review addresses the clinical pharmacokinetic aspects of drug therapy in haemodialysis patients and considers: (a) the effects of ESRD on the general pharmacokinetics of drugs; (b) dialysis clearance and its impact on drug and metabolite elimination; (c) the definition of dialysability and the criteria for evaluation of drug dialysability; (d) pharmacokinetic parameters which are useful in the prediction of drug dialysability; and (e) the application of pharmacokinetic principles to the adjustment of dosage regimens in haemodialysis patients. Finally, drugs commonly associated with haemodialysis therapy are tabulated with updated pharmacokinetics and dialysability information.

Drug prescribing in renal failure: dosing guidelines for adults

The data base for rational guidelines to safe, efficacious drug prescribing in adults with renal insufficiency are presented in tabular form. Current medical literature was extensively surveyed to provide as much specific information as possible. When information is lacking, however, recommendations are based on pharmacokinetic variables in normal subjects. Nephrotoxicity, important adverse effects, and special considerations in renal patients are noted. Adjustments are suggested for hemodialysis and peritoneal dialysis when appropriate.

Variability of beta-blocker pharmacokinetics in young volunteers

Plasma concentrations of metoprolol, propranolol oxprenolol, acebutolol and its metabolite diacetolol were measured after single oral doses in young health volunteers. In order to assessed the inter- and intra-subject variability the following pharmacokinetic parameters were compared: AUC0(24), Cmax, tmax and t 1/2. The smallest variation in inter-subject variability was seen with oxprenolol and acebutolol: intrasubject variability was more uniform. Female volunteers taking an oral contraceptive generally had higher AUC0(24) and Cmax values than those not. This finding reached statistical significance only for metoprolol AUC0(24).