Ranitidine Induced Hepatotoxicity: A Review

Drug induced liver injury (DILI) is a primary safety concern during drug discovery and those drugs which are found to be associated with severe adverse drug reactions (ADRs) are mainly withdrawal from the market. There are few drugs which have been withdrawn due to its severe ADRs reported over the period of time in the post-marketing surveillance (PMS) [summarized in Table 1] and Ranitidine (RAN) is one of them and it is found to be associated with idiosyncratic hepatotoxic reactions (Teschke et al., 2018). RAN is widely used in the treatment of gastrointestinal diseases and is one of the most frequently prescribed drugs worldwide (Chalasani et al., 2010). An estimated 34.2 ± 10.7 cases of DILI per 1 million people per year were reported in the Spanish DILI Registry. It has been observed that, amongst all the DILI cases about 53% had to be hospitalized, 2% undergone liver transplant, 10% and 5% had a chronic liver disease and acute liver disease respectively (Andrade et al., 2005). DILI is a major reason behind the withdrawal of various pharmaceutical products. RAN induced liver injury may be an associated factor for its withdrawal from pharmaceutical market (Kaplowitz et al., 2005). Based on its clinical characteristics, RAN induced hepatotoxicity can be classified as cholestatic (mainly an increase in alkaline phosphatase, ALP), hepatocellular (primarily an increase in alanine aminotransferase, ALT) and mixed hepatotoxicity depending upon the type of observed liver injury. Ranitidine Induced Hepatotoxicity: A Review


Introduction
Drug induced liver injury (DILI) is a primary safety concern during drug discovery and those drugs which are found to be associated with severe adverse drug reactions (ADRs) are mainly withdrawn from the market. There are few drugs which have been withdrawn due to its severe ADRs reported over the period of time in the post-marketing surveillance (PMS) [summarized in Table 1] and Ranitidine (RAN) is one of them and it is found to be associated with idiosyncratic hepatotoxic reactions (Teschke et al., 2018). RAN is widely used in the treatment of gastrointestinal diseases and is one of the most frequently prescribed drugs worldwide (Chalasani et al., 2010). An estimated 34.2 ± 10.7 cases of DILI per 1 million people per year were reported in the Spanish DILI Registry. It has been observed that, amongst all the DILI cases about 53% had to be hospitalized, 2% undergone liver transplant, 10% and 5% had a chronic liver disease and acute liver disease respectively (Andrade et al., 2005). DILI is a major reason behind the withdrawal of various pharmaceutical products. RAN induced liver injury may be an associated factor for its withdrawal from pharmaceutical market (Kaplowitz et al., 2005). Based on its clinical characteristics, RAN induced hepatotoxicity can be classified as cholestatic (mainly an increase in alkaline phosphatase, ALP), hepatocellular (primarily an increase in alanine aminotransferase, ALT) and mixed hepatotoxicity depending upon the type of observed liver injury.
p.40 Amit Bandyopadhyay Banerjee et al., J. Pharm. Tech. Res. Management Vol. 8, No. 1 (2020)  Scientific data showed that there are numerous drugs, such as Ranitidine, Cimetidine and Famotidine, which are responsible for induction of hepatotoxicity. Hepatic cellular dysfunction initiates various immunological reactions such as innate and adaptive immune responses.

Stress and/or damage to the hepatocytes may trigger the activation of Kupffer cells (KC), natural killer cells (NK) and natural killer T (NKT) cells which enhance the release of various pro-inflammatory mediators and chemokines
in the liver (Blazka et al., 1995;Blazka et al., 1996;Ishida et al., 2002). Although, RAN induced liver injury subsides after the termination of drug treatment, still it is a major diagnostic and therapeutic concern for doctors. Majority of RAN associated liver injury cases are not recognized during clinical trials, later on they are reported in post marketing surveillance. There is a lack of preclinical and clinical studies on ranitidine, but there are some case studies [summarized in Table 2] which evidenced that ranitidine therapy raises the risk of liver disorders (Alfirevic et al., 2012). The present review focuses on the possible mechanism behind the etiology of RAN induced liver toxicity and reason behind the withdrawal of RAN from the market.

History of Ranitidine Associated Toxicity
Ranitidine was first introduced by john Bradshaw in the UK as AH19065 in 1977 at the Ware research laboratories of Allen and Hanburys, division of a larger Glaxo organization (Lednicer, 1993). Further it was developed by Sir James Black at Smith, Kline and French in response to the first H2-receptor, antagonist, launched as Tagamet on November 1976 in United Kingdom. Furthermore, Glaxo developed the model with modification to the structure to nitrogen containing substituent, i.e. substituting the cimetidine imidazole ring with a furan ring and creating ranitidine. The tolerance level of RAN (i.e. fewer adverse reactions) was said to be much better and more powerful than cimetidine. RAN has about 10% interaction with cytochrome P 450 which indicates fewer side effects, but there are no major interactions with cytochrome P450 and other H2 blockers, such as nizatidine and famotidine (Newhouse, 1986). Ranitidine was the newly introduced and a United States Food and Drug Administration (US-FDA) approved H2 receptor antagonist for short-term oral use in duodenal ulcer therapy and in the Zollinger-Ellison syndrome in hypersecretory states (Med Lett, 1982). Few reports of clinical hepatotoxicity have been reported in Europe, Australia and Canada while undergoing oral preparation therapy and symptomatic liver disease have occurred in the United States during treatment with oral ranitidine (Barr, 1981;Cleator, 1983). A study showed that patients had symptomatic liver disease between 3 and 5 weeks after the ranitidine treatment, concerned symptoms like headache, "flu-like symptoms" (shaking chills and fever) and dark urine had also been observed for one day (Black et al., 1984).
Recently, on April 1, 2020, the presence of contaminants was recognized as N-Nitrosodimethylamine (NDMA), the US-FDA immediately demanded the manufacturers for withdrawal of all the over-the-counter (OTC) and prescription RAN products. However in some of the samples, the US-FDA failed to detect inappropriate NDMA levels, they found that the contamination of some ranitidine products increased over the course of the time, when stored at higher room temperatures. As a consequence, ranitidine products are banned for use in the US (Lim et al., 2020). NDMA (a cancer causative agent) is a possible human carcinogen, and low NDMA levels are normally consumed in diets. These levels, do not contribute to rise in cancer risk. The US-FDA conducted comprehensive testing on ranitidine and found a very low level of NDMA and suggested to avoid the use of Ranitidine products. In September 2019, the US-FDA concluded its analysis and informed the people about possible hazards and proposed alternative OTC and prescription therapies (Francis et al., 2005).

Molecular Mechanism Involved in Ranitidine Associated Hepatotoxicity
It is believed that RAN induced hepatotoxicity involves two pathways i.e. Immune mediated (Immunoallergic reactions) and direct cellular dysfunction. Though, the exact mechanism behind ranitidine induced hepatotoxicity still remains unclear (Bleibel et al., 2007), a schematic diagram concerned with the possible mechanism of RAN induced hepatotoxicty has been hypothesized in Figure 1. Amit Bandyopadhyay Banerjee et al., J. Pharm. Tech. Res. Management Vol. 8, No. 1 (2020) p.43

Immune-Mediated Liver Injury (Immunoallergic reactions)
The liver contains abundant sinusoidal macrophages i.e. Kupffer cells, which are responsible for the removal of foreign antigens, cellular debris and waste via hepatic portal system. It promotes the activation of cytotoxic T cells and induces apoptotic death of activated T cells and suppresses the immune response against these foreign antigens thereby increase immune tolerance (Maddrey et al., 2005). In case of ranitidine associated liver injury this process gets disrupted and results in impaired immune tolerance and generate altered autoantigens (Bleibel et al., 2007). These autoantigens binds to the surface of B-cells and forms MHC type I with hepatocytes via antigen-antibody reaction which subsequently causes induction of autoimmune reactions or antibody dependent immune response or B-cell mediated humoral response which is responsible for cellular destruction of hepatocytes via phagocytosis (Bleibel et al., 2007). In addition, these cellular immune responses triggers the release of pro-inflammatory mediators and various cytokines such as Tumour Necrosis Factor α (TNFα), nitrogen oxide (NO), FasL, and various interferons particularly IFN-γ (Kaplowitz et al., 2004).

Direct Cellular Damage
In majority of cases, RAN induced liver injury is triggered by chemically active toxic metabolite of drug which binds to cellular components such as lipids, proteins, nucleic acids and other cellular organelles leading to direct cellular dysfunction such as altered protein synthesis, nuclear damage and lipid peroxidation, which subsequently increases mitochondrial oxidative stress and promotes hepatocellular damage (Holt et al., 2006). Additionally, this direct cellular damage also increases the sensitivity of cells to the TNF receptor (Particularly TNFα) which triggers apoptotic cascade activation and induces apoptosis and promotes phagocytosis by the activation of cytotoxic T-cells (CD8) and leads to necrotic or apoptotic damage of hepatocytes. There is lot of phenotypic genetic variation amongst people; some people are vulnerable to RAN associated idiosyncratic reactions, whereas some are resistant. The microsomal P450 is responsible for the metabolism of RAN. Patients who lack cytochrome P450 enzyme are more prone to idiosyncratic reactions, because in the absence of cytochrome P450, metabolism of ranitidine is affected which leads to formation of its toxic metabolites and various intermediates which are responsible for hepatocellular damage (Kaplowitz et al., 2004).

Case Study Reports on Ranitidine Therapy
Ranitidine has been used for years in the treatment of gastrointestinal diseases and considered as the most prescribed drugs in the world. As DILIs are generally idiosyncratic, infrequent and unpredictable therefore difficult to induce in animal models therefore, either no or very fewer preclinical models have been developed for idiosyncratic DILI which makes it difficult to understand its exact pathogenesis (Chalasani et al., 2010). A few case studies have been tabulated in Table 2.

Steps Taken by Government and Any Regulations
US-FDA, European Medicines Agency (EMA), and Central Drugs Standard Control Organisation (CDSCO) have spotted the stringent content of nitrosamine in various products of RAN (Shaik et al., 2020). India's drug regulatory authority has ordered to withdraw samples of RAN, after the US regulator declared the presence of a cancer-causing impurity in some products (Woodcock, 2019

Conclusion
RAN induced liver injury is difficult to diagnose and study because of its relative rarity and unpredictive occurrence (Watkins et al., 2005). Recent studies suggest that most of the RAN associated idiosyncratic reactions may lead to hepatocyte damage, followed by a series of events, such as activation of specific T-and B-cells, release of proinflammatory mediators like TNFα, interleukins, various cytokines and chemokines. However RAN induced hepatotoxicity is selflimiting in majority of cases, if early diagnosis is not made, then it may develop into severe hepatic failure (Rashid et al., 2004). In a preclinical study, it was observed that ranitidine (30 mg/kg) did not produce liver injury in healthy animals; it was hepatotoxic in only those rats which are having mild inflammatory response induced by LPS (Luyendyk et al., 2003). The liver injury caused by RAN is usually rapidly reversible with cessation of the treatment. Gastroenterologists must be aware of the consequences before prescribing RAN to the patients who are already suffering from any liver diseases. The exact cause of RAN associated idiosyncratic hepatotoxicity is not clear yet. However, some studies suggest that the H2 receptor antagonists may be a potential cause for idiosyncratic hepatotoxic reactions; therefore it is not prescribed now-a-days. Due to the lack of preclinical and clinical studies on RAN associated liver injury, it is difficult to conclude the exact pathogenesis and the possible ADRs. However, Nitrosamines are genotoxic impurities, and due to their carcinogenicity, they pose an alarming threat to all creatures of earth. To alleviate this global issue, regulatory agencies such as CDSCO, US-FDA, and EMA have given their continuous effort for quantitative determination of amine impurities present in food stuffs, and in various intermediates in organic synthesis (Shaik et al., 2020). More studies must be carried out on this to know about the reason behind its hepatotoxicity.

Future Prospective
It is a topic of debate among various academicians and scientists "whether ranitidine will be available again in future or will FDA withdraw approvals of ranitidine (NDA) and An abbreviated new drug application (ANDA)?" However USFDA detected NDMA as a carcinogenic impurity still they failed to detect the optimum level or concentration at which it may harm the liver and other vital organs. There can be a possibility that RAN will come again in the market if the level of NDMA is found negligible or harmless concerned regarding patients health. There is a need to carry out more experimental studies in order to detect the optimum level of NDMA which is ultimately causing RAN associated hepatotoxicity.