Drugs and the ageing liver

Clinical course and outcomes of drug-induced liver injury: nimesulide as the first implicated medication

BACKGROUND AND AIMS

Drug-induced liver injury (DILI) is the most common cause of death from acute liver failure, and accounts for approximately 13% of cases of acute liver failure in the United States. The clinical presentation of DILI covers a wide spectrum, from asymptomatic liver test abnormalities to symptomatic acute liver disease, prolonged jaundice and disability, or overt acute or subacute liver failure. The aim of our study was to evaluate the number of DILI cases admitted to our Unit and to identify the drugs responsible. Thus, we reviewed all clinical records of patients with DILI admitted to our Unit from 1996 to 2006.

PATIENTS AND METHODS

A database was constructed, reporting demographic, clinical features at onset, laboratory results, suspected drugs and follow-up. Liver damage was defined as hepatocellular, cholestatic or mixed, according to clinical and laboratory data.

RESULTS

Forty-six patients were admitted with a diagnosis of DILI. Presentation was jaundice in 22 patients and hepatic failure in 3 (all attributed to nimesulide). Liver damage was of a cytolytic pattern in 19 cases (41%), cholestatic in 15 (33%) and mixed in 12 (26%). Jaundice was found to be higher in nimesulide-induced liver damage compared to other drugs (p=0.007). Three out of 14 patients with nimesulide-induced DILI developed encephalopathy and/or ascites. Time of recovery in the nimesulide group was significantly lower than DILI from other drugs (p<0.001).

CONCLUSION

Non-steroidal anti-inflammatory drugs, psychotropic drugs and antimicrobials are the most common causes of DILI. Nimesulide-induced DILI is usually reversible upon discontinuation of the drug, but occasionally progresses to liver failure.

Old age and the hepatic sinusoid

Morphological changes in the hepatic sinusoid with old age are increasingly recognized. These include thickening and defenestration of the liver sinusoidal endothelial cell, sporadic deposition of collagen and basal lamina in the extracellular space of Disse, and increased numbers of fat engorged, nonactivated stellate cells. In addition, there is endothelial up-regulation of von Willebrand factor and ICAM-1 with reduced expression of caveolin-1. These changes have been termed age-related pseudocapillarization. The effects of old age on Kupffer cells are inconsistent, but impaired responsiveness is likely. There are functional implications of these aging changes in the hepatic sinusoid. There is reduced sinusoidal perfusion, which will impair the hepatic clearance of highly extracted substrates. Blood clearance of a variety of waste macromolecules takes place in liver sinusoidal endothelial cells (LSECs). Previous studies indicated either that aging had no effect, or reduced the endocytic capacity of LSECs. However, a recent study in mice showed reduced endocytosis in pericentral regions of the liver lobules. Reduced endocytosis may increase systemic exposure to potential harmful waste macromolecules such as advanced glycation end products Loss of fenestrations leads to impaired transfer of lipoproteins from blood to hepatocytes. This provides a mechanism for impaired chylomicron remnant clearance and postprandial hyperlipidemia associated with old age. Given the extensive range of substrates metabolized by the liver, age-related changes in the hepatic sinusoid and microcirculation have important systemic implications for aging and age-related diseases.

Hepatotoxicity due to antibiotics

Antimicrobial drugs are important causative agents in idiosyncratic drug-induced liver injury (DILI). As with idiosyncratic DILI in general, antibiotic-induced liver injury is rare but difficult to diagnose and almost impossible to predict. Diagnosis requires awareness of possible causal agents, vigilance in monitoring symptoms and sometimes biochemical tests, attention to careful history taking and establishing temporal association, and exclusion of competing etiologies. In most instances, patients with antibiotic-associated DILI recover if the offending agent is withdrawn in a timely fashion.

Drug-induced liver injury in a Swedish University hospital out-patient hepatology clinic

BACKGROUND

Limited data exist on the proportion of drug-induced liver injury among out-patients seen in a hepatology clinic.

AIM

To determine the proportion of drug-induced liver injury cases, and identify the most important agents and the nature of the liver injury.

METHODS

A computerized diagnoses database in an out-patient hepatology clinic in a Swedish University hospital was analysed during the period 1995-2005. All suspected drug-induced liver injury cases were causality assessed with the International Consensus Criteria.

RESULTS

A total of 1164 cases were seen for the first time during this period. Drug-induced liver injury with at least a possible causal relationship was found in 77 cases (6.6%), 38 (3.3%) of whom were referred for evaluation to the out-patient clinic whereas 3% had a follow-up after hospitalization of drug-induced liver injury. The median age was 58 years, 43 (56%) were females, a hepatocellular pattern was observed in 37 cases (48%), cholestatic in 31 (40%) and mixed in 12%. Antibiotics were the most common agents causing drug-induced liver injury followed by non-steroidal anti-inflammatory drugs, with diclofenac most often responsible for the drug-induced liver injury.

CONCLUSIONS

Drug-induced liver injury cases constituted 6% of all out-patients and 3% of referrals and occurred more often in women. Antibiotics and diclofenac were the most common causes of drug-induced liver injury among out-patients.

Fulminant drug-induced hepatic failure leading to death or liver transplantation in Sweden

OBJECTIVE

There are only a few data on the prevalence of drug-induced liver injury associated with fatal outcome. The aim of this study was to determine the nature and number of suspected adverse drug-induced liver disease associated with fatalities and/or liver transplantation since reporting of adverse drug reactions (ADRs) started in Sweden.

MATERIAL AND METHODS

All reports of suspected hepatic ADRs with fatal outcome received by the Swedish Adverse Drug Reactions Advisory Committee (SADRAC) from 1966 to 2002 were reviewed and causality assessed.

RESULTS

The SADRAC received 151 reports of suspected ADRs with fatal outcome from liver injury; 48 cases were either unlikely or excluded. Of the remaining 103 cases, 13 (13%) were highly probable, 48 (47%) probable and 42 (41%) possible. The median age of the 103 patients was 64 years (47-77 interquartile range (IQR)) and 59 (57%) were males. The majority of cases were classified as hepatocellular (75%), with only 15% cholestatic and 10% mixed. Halothane, paracetamol, flucloxacillin, sulfamethoxazole/trimethoprim and diclofenac were the most common drugs associated with fatal outcome. Seventeen patients underwent liver transplantation, most commonly because of paracetamol and disulfiram toxicity.

CONCLUSIONS

A wide range of suspected ADRs are associated with fatalities. Antibiotics and analgesics are associated with the greatest number of reports of deaths.

Veterinary pharmacovigilance. Part 6. Predictability of adverse reactions in animals from laboratory toxicology studies

Toxicological studies are conducted on constituents of veterinary medicinal products for a number of reasons. Aside from being a requirement of legislation, they are carried out for predictive purposes in the assessment of user safety or for the determination of consumer safety, for example, in the elaboration of maximum residue limits or tolerances. Alternatively, the results of toxicology studies may be available as they have been generated for registration of the drug for human medicinal purposes. This paper examines if the results of such studies have any predictive value for adverse reactions, which might occur during clinical use in animals. A number of adverse reactions, notably the Type A (toxicology or pharmacology dependent) should be predictable from these laboratory studies. However, as with human pharmaceutical products, they have less utility in predicting Type-B reactions (idiosyncratic in nature).

Aging biology and geriatric clinical pharmacology

Population aging evokes doomsday economic and sociological prognostication, despite a minority of older people suffering significant dependency and the potential for advances in therapeutics of age-related disease and primary aging. Biological aging processes are linked mechanistically to altered drug handling, altered physiological reserve, and pharmacodynamic responses. Parenteral loading doses need only be adjusted for body weight as volumes of distribution are little changed, whereas oral loading doses in some cases may require reduction to account for age-related increases in bioavailability. Age-related reduction of hepatic blood flow and hepatocyte mass and primary aging changes in hepatic sinusoidal endothelium with effects on drug transfer and oxygen delivery reduce hepatic drug clearance. Primary renal aging is evident, although renal clearance reduction in older people is predominantly disease-related and is poorly estimated by standard methods. The geriatric dosing axiom, "start low and go slow" is based on pharmacokinetic considerations and concern for adverse drug reactions, not from clinical trial data. In the absence of generalizable dosage guidelines, individualization via effect titration is required. Altered pharmacodynamics are well documented in the cardiovascular system, with changes in the autonomic system, autacoid receptors, drug receptors, and endothelial function to modify baseline cardiovascular tone and responses to stimuli such as postural change and feeding. Adverse drug reactions and polypharmacy represent major linkages to avoidable morbidity and mortality. This, combined with a deficient therapeutic evidence base, suggests that extrapolation of risk-benefit ratios from younger adults to geriatric populations is not necessarily valid. Even so, therapeutic advances generally may convert healthy longevity from an asset of fortunate individuals into a general social benefit.

Liver disease in the elderly

Despite several morphologic and functional changes that have been described in the aging liver, most relevant studies fail to identify a significant age-related deficit in liver function in humans. One of the important age-related changes is a decrease in regenerative capacity, which may partly explain the impaired recovery after severe viral and toxic injury in the elderly. Nevertheless, livers from older subjects are used successfully for transplantation. Substantial morbidity and mortality in the elderly is attributable to liver diseases, and the number of patients older than 65 years of age with chronic liver disease is increasing rapidly. Although there are no liver diseases specific to advanced age, the presentation, clinical course and management of liver diseases in the elderly may differ in important respects from those of younger individuals.

Oral anticoagulants. Pharmacologic issues for use in the elderly

There has been a marked expansion of the indications for oral anticoagulant therapy, particularly among the elderly. Despite the documented benefits, the use of warfarin remains strikingly low among patients 80 years of age and older. Elderly patients often exhibit an enhanced dose response to warfarin. On average, steady-state warfarin doses decrease by 11% per decade of age. Pharmacokinetic changes in the elderly are negligible. Pharmacodynamic differences have not been well characterized. Initiating warfarin dosing in the elderly should be done cautiously, with doses of 5 mg or less. Doses should be adjusted downward in the presence of congestive heart failure, advanced obstructive lung disease, liver disease, malignancy, protracted diarrhea, enteral feedings, or concurrent potentiating medications. Numerous medications interfere with the anticoagulant response of warfarin. The most powerful potentiating drugs are those that interfere with the metabolism of (S)-warfarin. Examples include amiodarone, trimethoprim-sulfamethoxazole, and metronidazole. These drugs should be prescribed with caution in the elderly and mandate frequent INR monitoring during the induction period. An extensive assessment of patient-specific factors that might increase the hazards related to warfarin therapy needs to be conducted and documented before initiating oral anticoagulant therapy. Patients and their caregivers need to understand the risks and benefits, and to recognize signs of abnormal bleeding and the need for frequent monitoring. Patients should be encouraged to maintain consistency in their vitamin K intake and should strive to meet the recommended dietary allowance for vitamin K. To improve anticoagulation control, physicians and other health care providers need to be aware of the many warfarin drug interactions and be cognizant of the increased dose response of warfarin seen in the elderly. Concurrent prescription of multiple drugs known to affect warfarin's anticoagulant response should be minimized and use of nonselective nonsteroidal anti-inflammatory drugs should be limited given their deleterious effects on the gastric mucosa. Transitions from inpatient care to subacute care and back to outpatient care are particularly vulnerable periods for patients' anticoagulation control. Enhanced provider communication and more seamless transitions help to ensure optimal INR follow-up and timely warfarin dose adjustment if indicated.

Oxidative injury reproduces age-related impairment of oxygen-dependent drug metabolism

The Oxygen Diffusion Barrier Hypothesis states that aging in the liver is associated with restricted oxygen uptake that explains the age-related impairment of phase I drug clearance observed in vivo with preservation of in vitro phase I enzyme activity and in vivo phase II drug clearance. Aging in the liver may be secondary to oxidative stress. Therefore we examined the effects of oxidative injury on oxygen uptake, and phase I and phase II drug metabolism in the liver. Oxidative stress was induced in the perfused rat liver with hydrogen peroxide. The intrinsic clearances of propranolol and morphine were used as markers of phase I and phase II activity, respectively. Oxidative injury was associated with a 14+/-99% (P=0.03) reduction in oxygen uptake. The decrease in the intrinsic clearance of propranolol was greater than that of morphine (57+/-14% vs 34+/-7% P<0.005). This result supports the concept of a restriction of oxygen supply constraining hepatic drug metabolism following oxidative stress. This has implications for aging and hepatic drug metabolism.

The aging liver. Drug clearance and an oxygen diffusion barrier hypothesis

A change in drug clearance with age is considered an important factor in determining the high prevalence of adverse drug reactions associated with prescribing medications for the elderly. Despite this, no general principles have been available to guide drug administration in the elderly, although a substantial body of clearance and metabolism data has been generated in humans and experimental animals. A review of age-related change in drug clearances established that patterns of change are not simply explained in terms of hepatic blood flow, hepatic mass and protein binding changes. In particular, the maintained clearance of drugs subject to conjugation processes while oxygen-dependent metabolism declines, and all in vitro tests of enzyme function have been normal, requires new explanations. Reduction in hepatic oxygen diffusion as part of a general change in hepatocyte surface membrane permeability and conformation does provide one explanation for the paradoxical patterns of drug metabolism, and increased hepatocyte volume would also modify oxygen diffusion path lengths (the 'oxygen diffusion barrier' hypothesis). The reduction in clearances of high extraction drugs does correlate with observed reduction in hepatic perfusion. Dosage guidelines emerge from these considerations. The dosage of high clearance drugs should be reduced by approximately 40% in the elderly while the dosage of low clearance drugs should be reduced by approximately 30%, unless the compound is principally subject to conjugation mechanisms. If the hepatocyte diffusion barrier hypothesis is substantiated, this concept may lead to therapeutic (preventative and/or restorative) approaches to increased hepatocyte oxygenation in the elderly. This may lead to approaches for modification of the aging process in the liver.

Hepatotoxicity due to lysine salt of bendazac

BACKGROUND

The lysine salt of bendazac is a non-steroidal anti-inflammatory agent, and it is marketed exclusively for the treatment of cataracts. We report two cases of possible hepatotoxicity due to the use of bendazac lysine.

METHODS

Laboratory tests, serologic tests, abdominal sonography and scan were performed to study liver disease.

RESULTS

Reversible increases of the hepatic enzymes were found in both cases. Anemia was also found in one of the cases (case 1).

CONCLUSIONS

Abnormal liver test results could be related to a possible liver injury attributed to the use of bendazac lysine.

Hepatic injury associated with the use of nitrofurans: a clinicopathological study of 52 reported cases

Fifty cases of nitrofurantoin-associated hepatic injury and two cases of nifurtoinol (hydroxymethylnitrofurantoin)-associated hepatic injury reported to the Netherlands Centre for Monitoring of Adverse Reactions to Drugs were analyzed in detail. In 38 cases, a causal relationship was considered likely [i.e., "highly probable" (n = 4), "probable" (n = 23) or "possible" (n = 11)]. In 25 cases, hepatic injury was of the acute type whereas 13 cases presented a chronic type of reaction. Both types were more common in the elderly. Eighty per cent of the acute reactions appeared within the first 6 weeks of treatment and were sometimes accompanied by fever (28%), rash (12%) and eosinophilia (16%). Biochemically, the pattern was mainly hepatocellular (32%), whereas mixed cholestatic-hepatocellular (4%) and cholestatic (4%) patterns were uncommon. Although mild to moderate liver enzyme elevations (60%) were common, these were primarily symptomatic. The reaction was fatal in one "acute" and one "chronic" case. In the chronic cases, nuclear (82%) and smooth muscle (73%) antibodies and LE cells (50%) were frequently present. HLA typing showed no increase of the HLA B8 or HLA DRw3 haplotype. HLA DR2 (56%) and HLA DRw6 (56%) were more frequent than in controls (both 29%), but this was not statistically significant. Histology showed mainly necrosis, varying from spotty to massive, in the acute cases and a pattern consistent with chronic active hepatitis in the chronic cases.(ABSTRACT TRUNCATED AT 250 WORDS)