Respiratory symptoms related to work in a factory manufacturing cimetidine tablets

The management of work-related asthma guidelines: a broader perspective

The aim of the European Respiratory Society work-related asthma guidelines is to present the management and prevention options of work-related asthma and their effectiveness. Work-related asthma accounts for 5-25% of all adult asthma cases and is responsible for a significant socioeconomic burden. Several hundred occupational agents, mainly allergens but also irritants and substances with unknown pathological mechanisms, have been identified as causing work-related asthma. The essential message of these guidelines is that the management of work-related asthma can be considerably optimised based on the present knowledge of causes, risk factors, pathomechanisms, and realistic and effective interventions. To reach this goal we urgently require greatly intensified primary preventive measures and improved case management. There is now a substantial body of evidence supporting the implementation of comprehensive medical surveillance programmes for workers at risk. Those workers who fail surveillance programmes need to be referred to a clinician who can confirm or exclude an occupational cause. Once work-related asthma is confirmed, a revised risk assessment in the workplace is needed to prevent further cases. These new guidelines confirm and extend already existing statements and recommendations. We hope that these guidelines will initiate the much-needed research that is required to fill the gaps in our knowledge and to initiate substantial improvements in preventative measures.

Smoking and occupational asthma

Cigarette smoking is a known risk factor for many chronic illnesses such as coronary heart and chronic obstructive pulmonary diseases. Smoking is often described as a risk factor for occupational asthma even though its effect on the development of asthma is still under debate and the links between smoking and occupational asthma, occupational rhinitis or occupational sensitization are elusive, controversial and contradictory. This review describes these relationships in a wide range of occupations, from laboratory, farm, brewery and hospital workers, to bakers, printers, cleaners, fish processors and others as observed in cross-sectional, cohort, and case-control studies published over the past thirty-five years i.e. from 1970 to 2005. Surprisingly, the data show there is little to support the view that the risk of occupational asthma is increased in workers who are smokers. However, evidence emerges of an increased risk of occupational sensitization in smoking workers exposed to several high and low molecular weight agents. This in-depth review confirms the relationship between smoking and occupational asthma is complex and contradictory. It deserves more attention and further studies, which need to be conducted without being influenced by selection bias or by the justifiable prejudice against smoking.

Evidence based guidelines for the prevention, identification, and management of occupational asthma

BACKGROUND

Occupational asthma is the most frequently reported work related respiratory disease in many countries. This work was commissioned by the British Occupational Health Research Foundation to assist the Health and Safety Executive in achieving its target of reducing the incidence of occupational asthma in Great Britain by 30% by 2010.

AIM

The guidelines aim to improve the prevention, identification, and management of occupational asthma by providing evidence based recommendations on which future practice can be based.

METHODS

The literature was searched systematically using Medline and Embase for articles published in all languages up to the end of June 2004. Evidence based statements and recommendations were graded according to the Royal College of General Practitioner's star system and the revised Scottish Intercollegiate Guidelines Network grading system.

RESULTS

A total of 474 original studies were selected for appraisal from over 2500 abstracts. The systematic review produced 52 graded evidence statements and 22 recommendations based on 223 studies.

DISCUSSION

Evidence based guidelines have become benchmarks for practice in healthcare and the process used to prepare them is well established. This evidence review and its recommendations focus on interventions and outcomes to provide a robust approach to the prevention, identification, and management of occupational asthma, based on and using the best available medical evidence. The most important action to prevent cases of occupational asthma is to reduce exposure at source. Thereafter surveillance should be performed for the early identification of symptoms, including occupational rhinitis, with additional functional and immunological tests where appropriate. Effective management of workers suspected to have occupational asthma involves the identification and investigation of symptoms suggestive of asthma immediately they occur. Those workers who are confirmed to have occupational asthma should be advised to avoid further exposure completely and early in the course of their disease to offer the best chance of recovery.

Occupational airway sensitizers: an overview on the respective literature

BACKGROUND

Worldwide, there is rigorous scientific activity concerning the further development of work safety regulations involving airway-sensitizing substances. Technical directives on hazardous substances are enforced in several countries and are being continuously updated. The European Union has established a code for several occupational substances, now labeled R 42 ("may cause sensitization by inhalation").

METHODS

We present an overview of the literature dealing with allergic occupational asthma. The literature was selected according to criteria of study design and diagnostic test methods. Approximately 300 publications were reviewed including both epidemiological studies and individual case reports.

RESULTS

Airway sensitizers are systematically arranged and separately listed according to chemicals and their origin from animals, plants, and microorganisms. The clinical data as well as threshold limit values (TLV) and R 42 labeling of 250 airway-sensitizing substances are presented.

CONCLUSIONS

The most common sensitizing substances causing occupational asthma were dust of cereal flours, enzymes, natural rubber latex, laboratory animals as well as low molecular substances such as isocyanates and acid anhydrides.

Adverse reactions and interactions with H2-receptor antagonists

Histamine H2-receptor antagonists have been used in the treatment of gastrointestinal diseases for more than a decade and during this period have become one of the most commonly prescribed groups of drugs in the world. The deserved popularity of the H2-receptor antagonists reflects, in part, their therapeutic efficacy, which has revolutionised the treatment of peptic ulcer disease. An equally, or more, important reason for the widespread use of H2-receptor antagonists is their remarkably low toxicity. We have attempted, in this review, to present a detailed account of the minor and more serious adverse reactions, while emphasising the low incidence of the former and the rarity of the latter. The toxicology of the H2-receptor antagonists is discussed under two main headings: adverse effects; and drug interactions. The latter category is potentially the more significant, since the frequent use of therapy with multiple drugs may give rise to drug interactions, some of which are serious and may even be lethal. These drug interactions occur especially in the gastrointestinal tract, the liver and the kidneys. Thus, the absorption of other drugs may be altered because the H2-receptor antagonists inhibit gastric secretion--an effect illustrated by ketoconazole, the absorption of which is reduced when given in combination with cimetidine. Very important drug interactions are caused by inhibition of the hepatic microsomal enzyme cytochrome P450 by some of the H2-receptor antagonists. This effect appears to be related to the chemical structure of the individual H2-receptor antagonists and is not attributable to histamine H2-receptor blockade. For example, cimetidine is a powerful inhibitor of cytochrome P450, while the interaction of ranitidine with this system is weaker. Consequently, cimetidine reduces the metabolism of many drugs which are normally degraded by phase I reactions, leading to potentially toxic plasma concentrations of therapeutic agents such as some oral anticoagulants, beta-blockers, anticonvulsants, benzodiazepines and xanthines. Some of the H2-receptor antagonists are actively secreted by the renal tubules and may thus compete with other drugs for cationic tubular transport mechanisms, resulting in reduced urinary excretion and hence potentially toxic plasma concentrations. This type of drug interaction has been reported after administration of both cimetidine and ranitidine with procainamide or quinidine.(ABSTRACT TRUNCATED AT 400 WORDS)