Drug prescribing in hepatobiliary disease

Review article: prescribing medications in patients with cirrhosis - a practical guide

BACKGROUND

Most drugs have not been well studied in cirrhosis; recommendations on safe use are based largely on experience and/or expert opinion, with dosing recommendations often based on pharmacokinetic (PK) changes.

AIM

To provide a practical approach to prescribing medications for cirrhotic patients.

METHODS

An indexed MEDLINE search was conducted using keywords cirrhosis, drug-induced liver injury, pharmacodynamics (PDs), PKs, drug disposition and adverse drug reactions. Unpublished information from the Food and Drug Administration and industry was also reviewed.

RESULTS

Most medications have not been adequately studied in cirrhosis, and specific prescribing information is often lacking. Lower doses are generally recommended based on PK changes, but data are limited in terms of correlating PD effects with the degree of liver impairment. Very few drugs have been documented to have their hepatotoxicity potential enhanced by cirrhosis; most of these involve antituberculosis or antiretroviral agents used for HIV or viral hepatitis. Paracetamol can be used safely when prescribed in relatively small doses (2-3 g or less/day) for short durations, and is recommended as first-line treatment of pain. In contrast, NSAIDs should be used cautiously (or not at all) in advanced cirrhosis. Proton pump inhibitors have been linked to an increased risk of spontaneous bacterial peritonitis (SBP) in cirrhosis and should be used with care.

CONCLUSIONS

Most drugs can be used safely in cirrhosis, including those that are potentially hepatotoxic, but lower doses or reduced dosing frequency is often recommended, due to altered PKs. Drugs that can precipitate renal failure, gastrointestinal bleeding, SBP and encephalopathy should be identified and avoided.

Morbidity and mortality in cirrhotic patients undergoing anesthesia and surgery

Several studies have demonstrated increased morbidity and mortality in patients with cirrhosis undergoing anesthesia and surgery. Cirrhosis is a chronic liver disease, which may affect all body systems. The severity of the disease, assessed by the Child-Pugh classification, has a substantial effect on patient outcome. The extent of surgery and co-morbid conditions also have a major impact. In the past few years, changes have been made in the diagnosis, preoperative preparation, surgical and anesthetic management and perioperative care of patients with liver disease. The aim of this review is to examine whether these changes have resulted in improved perioperative outcomes.

Beta-Lactam antibiotic-induced leukopenia in severe hepatic dysfunction: risk factors and implications for dosing in patients with liver disease

PURPOSE

To determine if an association could be established for leukopenia and administration of beta-lactam antibiotic therapy in patients with hepatic dysfunction. If such an association could be found, to determine the incidence, timing, and risk factors for beta-lactam antibiotic-induced leukopenia.

PATIENTS AND METHODS

Patients with hepatic dysfunction, i.e., liver transplant recipients as well as patients with end-stage liver disease awaiting liver transplantation, seen at our institution between October 1989 and October 1991, who received 7 or more days of antibiotics, were studied in a prospective observational fashion. Complete blood count was determined at baseline and followed until the completion of the antibiotic course or until the resolution of leukopenia in leukopenic patients.

RESULTS

Leukopenia occurred after a mean of 6 days with 23% of the beta-lactam antibiotic courses as compared with 0% with the non-beta-lactam antibiotic courses (p = 0.046). Development of leukopenia correlated with the severity of liver disease. Patients developing leukopenia had worse synthetic hepatic function as evidenced by a lower serum albumin level (p < 0.01), a lower serum cholesterol level (p < 0.05), and a higher prothrombin time (p < 0.01) as compared with the patients without leukopenia. Leukopenic patients had a lower baseline white blood cell count (p < 0.051) and a lower baseline platelet count (p < 0.01) indicative of a greater degree of hypersplenism. Leukopenic patients received a higher mean daily dosage of cephalosporins as compared with nonleukopenic patients.

CONCLUSION

beta-Lactam antibiotics when administered in usually recommended dosages can induce leukopenia in patients with hepatic dysfunction. The probable mechanism is impaired hepatic metabolism of the beta-lactam antibiotics resulting in bone marrow suppression of white cell precursors from excessive antibiotic concentrations. The more severe the hepatic dysfunction, the greater the risk. We propose a reduction in dosages of beta-lactam antibiotics when used in patients with hepatic dysfunction. Finally, we raise the possibility that this adverse drug effect is more common than currently recognized by physicians.

Drug disposition in patients with HBsAg-positive chronic liver disease

Chronic infection with hepatitis B virus (HBV) results in a spectrum of hepatic abnormalities ranging from minimal liver dysfunction to severe liver failure. These patients provide an opportunity to examine the relationship between the evolution of the liver disease and the ability to metabolize drugs. We have examined hepatic drug disposition in patients with chronic persistent hepatitis, chronic active hepatitis, and cirrhosis due to HBV infection. Four model drugs were used: two low-extraction capacity-limited drugs (antipyrine and aminopyrine) and two high-extraction flow-limited drugs (ICG and lidocaine). The disposition of the four drugs tested was comparable to that of healthy controls in patients with chronic persistent hepatitis, chronic active hepatitis, and mild cirrhosis. In patients with severe cirrhosis (as defined by the presence of ascites, encephalopathy, or large esophageal varices), there was a significant impairment in the aminopyrine breath test (-31%) and in the clearance of antipyrine (-53%), lidocaine (-49%), and ICG (-54%). These results indicate that impairment of drug clearance occurs only late in the evolution of HBV-related chronic liver disease. This is in keeping with the known slow and insidious progression of the disease.

The effects of age and chronic liver disease on the elimination of temazepam

The pharmacokinetics of the newer 1, 4 benzodiazepine temazepam were evaluated in 16 healthy subjects aged 18-92 years and in 15 cirrhotic patients, to ascertain the effect of ageing and liver disease. The data were analysed both by classic two compartment and by non-compartmental methods. The mean elimination half-life in the control subjects was 15.5 h, considerably longer than previous estimates. No correlation was found between age and pharmacokinetic parameters. The cirrhotic group showed no statistically significant difference in the pharmacokinetic parameters nor in the urinary recovery of the dose from the control group. Temazepam plasma protein binding was assessed in a second group of 9 cirrhotics of similar severity to the main group and in matched controls. When these binding data were applied to the mean clearance data, a modest although not statistically significant, reduction in free drug clearance was observed in the cirrhotic group. This study adds further support to the observation that drugs which undergo ether glucuronidation have normal elimination patterns in patients with liver disease. Temazepam may prove to be a useful hypnotic sedative in patients with liver disease.

An intensive drug monitoring study suggesting possible clinical irrelevance of impaired drug disposition in liver disease

1 Liver disease can alter the disposition and clinical effects of drugs. However, even though altered drug disposition occurs, there is no clinical evidence relating it to an increased susceptibility to adverse drug reactions (ADRs). 2 An intensive prospective drug monitoring study of 2,582 hospitalized patients was conducted. The adverse drug reactions probability scale (APS) was used to assess ADRs. Only non-mild, definite or probable ADRs (APS greater than or equal to 5) were included. Severity of liver dysfunction was assessed by a composite clinical and laboratory index (CCLI). 3 The frequency of ADRs was higher in 402 patients with cirrhosis (27.4%) than in 661 with renal dysfunction (22.8%) and in 249 with other parenchymatous liver diseases (13.7%) or in 1,270 patients with neither liver diseases nor renal dysfunction (10.9%) (chi 2 3 = 85.53, P less than 0.001). The frequency of ADRs in cirrhotics was highly correlated with the severity of the liver dysfunction measured by CCLI (r = 0.82, P less than 0.001). 4 Drugs predominantly eliminated by liver metabolism were not among those most commonly inducing ADRs or those causing severe reactions in cirrhotics. Thus, frusemide caused the most common and the most severe ADRs, whereas reactions induced by sedatives were uncommon. Drug-induced hepatic encephalopathy was more common in cirrhotics receiving diuretics (13.3%) than in those receiving sedatives (1.8%) (chi 2 y.c. = 5.29, P less than 0.025). Patients with alcoholic liver disease had more drug-induced hepatic encephalopathy (7.7%) than those with non-alcoholic liver disease (1.2%) (chi 2 y.c. = 11.86, P less than 0.001). 5 These results indicate that susceptibility to ADRs is increased only in severe cirrhosis and that the most common and severe ADRs seem more likely related to enhanced pharmacodynamic action than to impaired drug disposition.

Host factors influencing the response to antimicrobial agents

When the desired clinical response to an antibiotic therapeutic regimen is not achieved, despite appropriate antibiotic selection and organism sensitivity, the clinician must be aware that several host factors exist that may influence the outcome. Examples of the influence of host-related factors on drug disposition have been briefly reviewed in this article. It should be noted, however, that further investigation is needed to determine whether these factors truly exert a significant influence on the outcome of antibiotic utilization.

Pharmacokinetics and bioavailability of cimetidine in humans

Cimetidine given orally without food after an overnight fast produces a blood concentration curve with a pronounced second peak that does not appear after parenteral administration or when the drug is taken with food. The following interpretation of this kinetic phenomenon is proposed: 1. The drug cumulates in a tissue or organ that is well perfused in the first-pass transfer. 2. The hepatic parenchymal tissue and the bile phase are the most likely storage areas. 3. The high capacity of the cumulation may be due to the formation of conjugates or other modifications of the drug with a pronounced affinity for the hepatic-biliary system. 4. The rate of cumulation is much higher in the first-pass transfer than from the systemic circulation, possibly due to the difference in the drug concentrations and the conjugation rate. 5. The cumulation appears to occur by a competitive process. 6. Absorbed elements of food seem to compete in this process. 7. The second peak apparently is the result of a rapid release of drug and bioreversible drug compounds from the hepatic-biliary system with subsequent reabsorption. 8. This release may occur spontaneously but appears to be triggered by food intake. A pharmacokinetic model constructed according to this interpretation showed good agreement with data from oral, intravenous, and intramuscular administration. The special problems associated with the evaluation of bioavailability in the presence of reabsorption are discussed.

Impaired elimination of caffeine in cirrhosis

The effect of cirrhosis on the disposition and elimination of caffeine was examined. Caffeine (250 mg) was administered orally to 15 healthy controls and eight patients with cirrhosis. The elimination half-life was prolonged from 5.2 +/- 2.4 hr (mean +/- SD) in controls to 6.1 +/- 1.9 hr in cirrhotics, although this did not reach statistical significance. The plasma clearance, however, was significantly higher (1.4 +/- 0.5 ml/min/kg) in controls as compared to cirrhotics (0.9 +/- 0.3 ml/min/kg) (P less than 0.05). The plasma binding of caffeine was also lower in cirrhotics (31.3 +/- 1.8% vs 25.5 +/- 4.0%, P less than 0.01). The plasma clearance of unbound caffeine therefore was reduced from 2.0 +/- 0.7 ml/min/kg in controls to 1.2 +/- 0.4 ml/min/kg (P less than 0.01) in cirrhotics, demonstrating impaired elimination of caffeine in cirrhosis.