|Oral Rehydration Therapy and the Control of Diarrheal Diseases (Peace Corps, 1985, 566 pages)|
|Module Two: Diarrhea, dehydration and rehydration|
|Session 5 - Rehydration therapy|
Professor Harold explains the clinical situations which justify the use of drugs in addition to oral rehydration therapy.
Two main groups of drugs are commonly prescribed in the treatment of diarrhoeal diseases:
· Antimicrobial drugs - which kill the responsible organism and so lessen the illness.
· Antidiarrhoeal drugs - which diminish the amount of fluid loss by various pharmacological mechanisms.
These two types of drugs are often combined and many preparations are marketed containing both antibiotics and antidiarrhoeal drugs. These combination drugs should never be used.
Only single drugs should be given and only where appropriate.
Antibiotics in bowel infections
For certain specific infections of the gut an appropriate antimicrobial drug is an important part of the treatment.
Shigella infection: in mild, transient diarrhoea caused by shigella, antibiotic treatment may be unnecessary as, for example, in mild Sonne or flexneri dysentery. Antibiotics are, however, an essential part of the treatment of severe bacillary dysentery especially in infants with persistent high fever. Choice is difficult because transferable drug resistance has become very common in these organisms and local knowledge of their drug susceptibility has to be taken into account. Ampicillin or co-trimoxazole are usually suitable (ampicilin 100 mg/kg/day in four divided doses for five days, or trimethoprim 10 mg and sulfamethoxazole 50 mg/kg/day in two divided doses for five days). Single dose treatment in adults with tetrad cycling (2.5g) is also very effective if the bacilli are known to be susceptible to this drug.
Campylobacter infection: Campylobacter jejuni may invade the bowel wall causing abdominal pain and mildly dysenteric stools. Most cases recover well without chemotherapy. Severe cases may be treated with erythromycin (40 mg/kg/day in three divided doses for five days) but its efficacy is unproved. A recent controlled trial showed no clinical benefit from erythromycin but treatment was not started until an average of six days from the onset of illness. (1)
Cholera: Several antibiotics, particularly tetracycline, have been shown to shorten the duration of the disease and are therefore useful in the management of cholera patients. Tetracycline is given as 50 mg/kg/day in four divided doses for three days. Drug resistance is now being seen in areas where mass chemoprophylaxis has been carried out. Alternative drugs include furazolidine and chloramphenicol.
Enterotoxigenic and enteropathogenic E. coli: Relatively few clinical trials have been done on the effect of antibiotics in this group of bowel infections. Enterotoxigenic E. cold generally cause acute episodes of relatively brief duration, making antibiotics unnecessary. Because of the difficulty in identifying these organisms, there seems to be little justification at the moment for treating them with antibiotics. Similarly, for enteropathogenic E. coli, there is no clear evidence that antibiotics are beneficial
Salmonella infections: For the vast majority of acute diarrhoeal illnesses caused by nontyphoid Salmonella strains. antibiotics do not change the course of illness and may actually prolong the period during which stool cultures remain positive. Salmonella septicaemia. which may present in childhood as a combination of diarrhoea with systemic illness and fever requires antibiotic treatment. Ampicillin, chloromycetin, or co-trimoxazole may be used, depending on the sensitivity of the organism.
Amoebiasis and Giardiasis: Both these parasitic infections respond to several antimicrobial agents. Metronidazole is the first choice for either.
Antibiotics in bowel infections of unknown cause
The cause of many bowel infections is never identified, or the organism may be found after the acute illness is over. Antibiotics have no role in the treatment of the large group of viral diarrhoeas. It has sometimes been suggested that antibiotics should routinely be prescribed in case the illness turns out to be due to an infection for which antibiotic treatment is indicated.
This practice is to be avoided for several reasons:
· The giving of antibiotics may divert the attention of mother and nurse from the essential task of replacing water and electrolytes.
· The widespread use of antimicrobials promotes the selection of antibiotic resistant strains and thus lessens the likelihood that the drugs will later be effective for those few patients who need them.
· Antibiotics are expensive.
The balance of factors therefore clearly lies against the blind use of antibiotics in diarrhoeal disease of unknown origin.
Other drugs in gastroenteritis
The most commonly used agents are kaolin and pectin in one or other of many available preparations, despite clinical trials proving lack of efficacy. Most children improve so quickly with fluid and electrolyte replacement that the use of 'constipating agents is unnecessary in acute diarrhoea.
Drugs such as opiates, diphenoxylate and loperamide which reduce bowel motility. although widely used, should never be given to children. By slowing peristalsis they make the situation worse - this has been seen in a number of children and in volunteers with shigellosis. These drugs also depress respiration and are an important cause of accidental poisoning in childhood
Several research projects arc underway aiming to find drugs which will reduce the abnormal transport of fluid across the small bowel mucosa. For example, anti-inflammatory drugs (aspiring and indomethacin) may decrease the action of cholera and other toxins acting on the trowel. Bismuth subsalicylate, in large doses, has been beneficial in adults with travellers' diarrhoea.
Other substances have also been tried; for example, chlorpromazine, which probably inhibits adenylate cyclase, was shown to reduce diarrhoeal losses in cholera. However, since it may cause drowsiness in children and hence a decrease in fluid in lake. it is unsuitable for widespread use Attempts have also been made to prevent cholera toxin binding to the bowel wall, but these studies have not shown the method to be useful in practice.
None of these experimental drugs have reached a stage where they can be recommended for general use in patients with diarrhoea. If drugs which reduce intestinal secretion become better defined, and can be shown to be effective in field conditions against diarrhoea caused by 8 broad range of aetiologic agents, they will be useful adjuncts to therapy.
Oral rehydration therapy- remains the essential treatment and antibiotics arc useful only in the few clinical situations described.
Professor H.P. Lambert, Communicable Diseases Unit, St.
George's Hospital-London UK.
(1) Andres BJ et al 1982 Double-blind placebo controlled trial of erythromycin for treatment of campylobacter enteritis. The Lancet January 16: 131-132
(From: Diarrhoea Dialogue, Issue 8, February 1982, pp.4-5)