Acute isoniazid neurotoxicity during preventive therapy

Polymorphisms in drug metabolism genes as a risk factor for first-line anti-tuberculosis drug-induced liver injury

BACKGROUND

Anti-tuberculosis drug-induced liver injury (AT-DILI) is one of the most common side effects in TB patients during treatment. The prime cause of liver injury during TB treatment is reported to be isoniazid and its metabolites. Different factors influenced the development of AT-DILI, and genetic factors are one of the major factors.

METHODS AND RESULTS

Polymorphisms in drug metabolism genes like NAT2, CYP2E1, PXR, and GST have been reported to be associated with AT-DILI, and they are one of the major areas of focus at present. Attempts are met in this review to analyse the different markers in these drug metabolism genes for their association with AT-DILI.

CONCLUSION

A better understanding of the polymorphisms in these genes and their functional effects will give better insights into the development of AT-DILI, and it could facilitate in designing and developing more effective personalized treatment for TB.

Seizures, Metabolic Acidosis and Coma Resulting from Acute Isoniazid Intoxication

Isoniazid is an anti-tuberculosis drug, used commonly for treatment and prophylaxis of tuberculosis. Acute isoniazid intoxication is characterized by a clinical triad consisting of metabolic acidosis resistant to treatment with sodium bicarbonate, seizures which may be fatal and refractory to standard anticonvulsant therapy, and coma. Treatment requires admission to the intensive care unit for ventilatory support, management of seizures and metabolic acidosis. Pyridoxine, in a dose equivalent to the amount of isoniazid ingested, is the only effective antidote. We report the successful treatment of two isoniazid intoxication cases: the case of a child developing an accidental acute isoniazid intoxication and an adult case of isoniazid intoxication with the intent of suicide.

[The chemical toxicological determination of isoniazid and metoclopramide in the objects used for animals poisoning and in biological fluids]

The number of mass casualty incidents among the dogs has significantly increased during a few recent years in the cities of this country; they are most frequently attributed to the activities of the so-called dog hunters. The dog hunters make use of a variety of chemical compounds for poisoning the dogs. Most of them are the multi-component substances, with their chemical composition being highly variable and continuously modified. The objective of the present study was to develop the method for the isolation and identification of isoniazid and metoclopramide introduced into the baits that are distributed by the dog hunters for the poisoning of the animals. The proposed method was tested with the use of biological fluids obtained from the laboratory animals. The effectiveness of isolation of the compounds of interest from these materials with the use of the liquid-liquid and fractional freezing extraction techniques was evaluated. In addition, the method for solid phase extraction with the use of the 'Oasis HLB' cartridges was developed.

Isoniazid overdose : a case series, literature review and survey of antidote availability

Tuberculosis has re-emerged as a significant public health threat over the last decade both globally and within Australia. This is thought to be largely due to the HIV epidemic, a growing itinerant population, and immigration. The antibiotic isoniazid remains an integral part of drug therapy. With the numbers of patients receiving isoniazid remaining high, the number of cases of acute poisoning is expected to be significant. This paper presents a series of two cases of isoniazid poisoning presenting to a tertiary referral centre in North Queensland. Isoniazid toxicity produces a triad of coma, metabolic acidosis and seizures. The seizures are often refractory to traditional antiepileptics. A specific antidote is available (pyridoxine [vitamin B6]) and both patients were administered this as part of their treatment. We also surveyed all hospitals in Australia with an accredited adult Emergency Department to assess the availability of pyridoxine.

Advances pertaining to the pharmacology and interactions of irreversible nonselective monoamine oxidase inhibitors

Recent advances clarifying the pharmacology and interactions of irreversible nonselective monoamine oxidase inhibitors that have not been considered in depth lately are discussed. These new data elucidate aspects of enzyme inhibition and pharmacokinetic interactions involving amine oxidases, cytochrome P450 enzymes, aminotransferases (transaminases), and decarboxylases (carboxy-lyases) and the effects of tyramine. Phenelzine and tranylcypromine remain widely available, and many publications have data relevant to this review. Their effect on CYP 450 enzymes is less than many newer drugs. Tranylcypromine only inhibits CYP 450 2A6 (selectively and potently). Phenelzine has no reported interactions, but, like isoniazid, weakly and irreversibly inhibits CYP 450 2C19 and 3A4 in vitro. It might possibly be implicated in interactions (as isoniazid is). Phenelzine has some clinically relevant inhibitory effects on amine oxidases, aminotransferases, and decarboxylases, and it lowers pyridoxal phosphate levels. It commonly causes pyridoxal deficiency, weight gain, sedation, and sexual dysfunction, but only rarely causes hepatic damage and failure, or neurotoxicity. The adverse effects and difficulties with monoamine oxidase inhibitors are less than previously believed or estimated, including a lower risk of hypertension, because the tyramine content in foods is now lower. Potent norepinephrine reuptake inhibitors have a strong protective effect against tyramine-induced hypertension. The newly discovered trace amine-associated receptors probably mediate the pressor response. The therapeutic potential of tranylcypromine and L-dopa in depression and Parkinson disease is worthy of reassessment. Monoamine oxidase inhibitors are not used to an extent proportionate with their benefits; medical texts and doctors' knowledge require a major update to reflect the evidence of recent advances.

Neuroimaging findings in isoniazid central nervous system toxicity, presumed intramyelinic edema

We describe the clinical course and striking neuroimaging findings of a child with central nervous system toxicity due to isoniazid. Serum isoniazid level was in the toxic range, the result of a dispensing error as well as a possible pharmacogenetic factor. We postulate that these imaging findings were the result of intramyelinic edema, previously described in experimental animal models of isoniazid toxicity.

Tuberculosis in patients with systemic rheumatic or pulmonary diseases treated with glucocorticosteroids and the preventive role of isoniazid: a review of the available evidence

Development of tuberculosis (TB) is a concern in patients who receive glucocorticosteroids for the treatment of chronic rheumatic or pulmonary diseases. However, the incidence of development of TB in such patients and the prophylactic role of isoniazid (INH) are unclear. We evaluated the available evidence from 20 relevant prospective and retrospective cohort and case-control studies identified in the PubMed and Cochrane databases. The frequency of development of TB in the populations studied varied from 0% to 13.8%. This figure was low in studies performed in countries with a low incidence of TB (0% in the USA and Greece, 0.6% in France and 1.35% in Spain). In contrast, the frequency of development of TB in the studied cohorts was high in studies performed in countries with a moderate to high incidence of TB (from 2.5% in South Korea to 13.8% in The Philippines). Isoniazid prophylaxis (INHP) was found to decrease the incidence of development of TB in two of four studies that examined this intervention. The available evidence suggests that patients who receive steroids for the treatment of chronic rheumatic or pulmonary diseases and who live in countries with a high incidence of TB have a high risk of development of TB in contrast to patients who live in countries with a low incidence of the infection. However, the role of INHP even for patients living in countries where TB is endemic is unclear because the effectiveness of INH in preventing TB development in such patients is not well established and there are cost-effectiveness and safety issues.

CYP2E1 genotype and isoniazid-induced hepatotoxicity in patients treated for latent tuberculosis

OBJECTIVE

To determine whether pharmacogenetic tests such as N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) genotyping are useful in identifying patients prone to antituberculosis drug-induced hepatotoxicity in a cosmopolite population.

METHODS

In a prospective study we genotyped 89 patients treated with isoniazid (INH) for latent tuberculosis. INH-induced hepatitis (INH-H) or elevated liver enzymes including hepatitis (INH-ELE) was diagnosed based on the clinical diagnostic scale (CDS) designed for routine clinical practice. NAT2 genotypes were assessed by fluorescence resonance energy transfer probe after PCR analysis, and CYP2E1 genotypes were determined by PCR with restriction fragment length polymorphism analysis.

RESULTS

Twenty-six patients (29%) had INH-ELE, while eight (9%) presented with INH-H leading to INH treatment interruption. We report no significant influence of NAT2 polymorphism, but we did find a significant association between the CYP2E1 *1A/*1A genotype and INH-ELE (OR: 3.4; 95% CI:1.1-12; p = 0.02) and a non significant trend for INH-H (OR: 5.9; 95% CI: 0.69-270; p = 0.13) compared with other CYP2E1 genotypes. This test for predicting INH-ELE had a positive predictive value (PPV) of 39% (95% CI: 26-54%) and a negative predictive value (NPV) of 84% (95% CI: 69-94%).

CONCLUSION

The genotyping of CYP2E1 polymorphisms may be a useful predictive tool in the common setting of a highly heterogeneous population for predicting isoniazid-induced hepatic toxicity. Larger prospective randomized trials are needed to confirm these results.

Proton pump inhibitor formulary considerations in the acutely ill. Part 2: Clinical efficacy, safety, and economics

OBJECTIVE

To review, using an evidence-based approach, the clinical efficacy, safety, and cost-effectiveness of proton pump inhibitors (PPIs) for treatment of common acid peptic disorders in the acutely ill and provide clinicians with guidance when making hospital formulary decisions with this class of agents.

DATA SOURCES

MEDLINE (1966-May 2005) and the Cochrane Library databases were searched using the key words proton pump inhibitor, acid suppression, peptic ulcer disease, gastrointestinal bleeding, stress ulcer prophylaxis, critical care, safety, and cost-effectiveness. Bibliographies of cited references were reviewed, and a manual search of abstracts from recent gastroenterology, critical care, and surgery scientific meetings was completed.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated, and all information deemed relevant was included for this review.

DATA SYNTHESIS

PPIs have become a mainstay for acute acid suppression in hospitalized patients. Various commercially available PPI products are available either enterally or parenterally for administration to patients unable to swallow a tablet or capsule. The results of studies comparing the clinical efficacy of different PPI dosage forms and routes of administration, safety considerations, and cost-effectiveness analyses are among the factors to consider when making formulary decisions for this class of drugs.

CONCLUSIONS

While the introduction of new PPI products has expanded the therapeutic options for acid suppression in acutely ill patients, a number of unresolved questions remain surrounding the interchangeability of these products, the clinical significance of one PPI formulation over the other, and how oral/enteral therapy should be used as step-down therapy after parenteral therapy.

The effects of isoniazid on hippocampal NMDA receptors: Protective role of Erdosteine

Isoniazid (INH) has neurotoxic effects such as seizure, poor concentration, subtle reduction in memory, anxiety, depression and psychosis. INH-induced toxic effects are thought to be through increased oxidative stress, and these effects have been shown to be prevented by antioxidant therapies in various organs. Increased oxidative stress may be playing a role in these neurotoxic effects. N-methyl D-aspartat receptors (NMDA) are a member of the ionotropic group of glutamate receptors. These receptors are involved in a wide variety of processes in the central nervous system including synaptogenesis, synaptic plasticity, memory and learning. Erdosteine is a potent antioxidant and mucolytic agent. We aimed to investigate adverse effects of INH on rat hippocampal NMDAR receptors, and to elucidate whether erdosteine prevents possible adverse effects of INH. In the present study, compared to control group, NMDAR2A (NR2A) receptors were significantly decreased and malondialdehyde (MDA), end product of lipid peroxidation, production was significantly increased in INH-treated group. On the other hand, administration of erdosteine to INH-treated group significantly increased NR2A receptors and decreased MDA production. In conclusion, decreasing NR2A receptors in hippocampus and increasing lipid peroxidation correlates with the degree of oxidative effects of INH and erdosteine protects above effect of INH on NR2A receptors and membrane damage due to lipid peroxidation by its antioxidant properties.

Proton pump inhibitor formulary considerations in the acutely ill. Part 1: Pharmacology, pharmacodynamics, and available formulations

OBJECTIVE

To review important proton pump inhibitor (PPI) pharmacologic, pharmacokinetic, and pharmacodynamic principles in acutely ill patients, compare PPI formulation options for patients unable to swallow a tablet or capsule, and provide clinicians with guidance when making hospital formulary decisions with this class of agents.

DATA SOURCES

MEDLINE (1966-May 2005) and the Cochrane Library databases were searched using the key words proton pump inhibitor, acid suppression, peptic ulcer disease, gastrointestinal bleeding, stress ulcer prophylaxis, and critical illness. Bibliographies of cited references were reviewed, and a manual search of abstracts from recent gastroenterology, critical care, and surgery scientific meetings was completed.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated, and all information deemed relevant was included for this review.

DATA SYNTHESIS

PPIs have become a mainstay for acute acid suppression in hospitalized patients over other therapeutic options. Various commercially available PPI products are available for administration, either enterally or parenterally, to patients unable to swallow a tablet or capsule. Newer oral PPI formulations offer numerous advantages over older products. The results of studies comparing the pharmacokinetics and pharmacodynamics of different PPI dosage forms and routes of administration are among the factors to consider when making formulary decisions.

CONCLUSIONS

While the introduction of new PPI products has expanded the therapeutic options for acid suppression in acutely ill patients, a number of unresolved questions remain surrounding the interchangeability of these products, the clinical significance of one PPI formulation over the other, and how oral/enteral PPI therapy should be used as step-down therapy after parenteral PPI therapy.

Melatonin prevents the free radical and MADD metabolic profiles induced by antituberculosis drugs in an animal model

The objective was to determine the effect of combined antituberculosis (anti-TB) drug therapy and an antioxidant, melatonin, on the free radical and organic acid profiles in an experimental rat model. A combined anti-TB drug, Rifater, consisting of 12.0 mg rifampicin, 0.8 mg isoniazid, and 23.0 mg pyrazinamide and 18.56 microg melatonin/kg body weight per day (corresponding to average physiological human intake) were orally administered to Sprague-Dawley rats. Hydroxyl radical production was monitored by quantifying 2,3-dihydroxybenzoic acid produced after intraperitonial sodium salicylate injections. Organic acid extractions and gas chromatography-coupled mass spectrometry analyses were performed on collected urine samples. The results show hydroxyl radicals (P = 0.0019) and organic acids (P-value range: 0.037 to <0.001), characteristic of a multiple acyl-CoA dehydrogenase defect (MADD), were elevated with Rifater treatment and these elevations were significantly lowered with melatonin pretreatment (P-value range: 0.031 to <0.001), probably because of its inherent antioxidant activity. We conclude that hydroxyl radical production and an increased organic acid profile induced by anti-TB medication indicates inhibition of the electron transport chain. We also conclude that free radicals leading to clinical symptoms associated with an MADD metabolic profile induced by anti-TB treatment could be alleviated by melatonin intervention.

Somatic complaints and isoniazid (INH) side effects in Latino adolescents with latent tuberculosis infection (LTBI)

This study examined the potential effects of INH side effects and non-specific somatic complaints on medication adherence in 96 Latino adolescents participating in a controlled trial designed to increase isoniazid (INH) adherence. These participants (who received usual medical care) were interviewed monthly over 9 months. Participants were questioned regarding medication taking, the frequency of 15 INH-related side effects from the Physician's Desk Reference (PDR) [1], and 21 non-specific somatic complaints. Participants were aged 12-19 years, 53.1% were male, 66.7% were born in Mexico, 73% had no health insurance, and 52.5% were classified as bicultural. Approximately 70% of participants experienced at least one side effect during the trial. Side effects that occurred while taking INH were not significantly related to total number of pills taken; somatic complaints that occurred during 9 months of INH were significantly negatively related to cumulative adherence. Females reported significantly more somatic complaints at baseline than males.