This content was published in 2012.
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For a more recent article covering the pharmaceutical considerations for patients with stomas, see here.
Stomas are surgically created, artificial openings that are often formed to connect a part of the gastrointestinal (GI) tract to the surface of the skin on the abdomen.
Understanding the type and extent of surgical intervention in each patient is crucial in managing his or her pharmaceutical needs correctly. The type of stoma relates to the section of the GI tract that opens through the wall of the abdomen. Colostomies and ileostomies are most common but it is also possible to have a gastrostomy, jejunostomy, duodenostomy or caecostomy.
This article is a practical guide to caring for patients with stomas formed in the lower GI tract, such as ileostomies and colostomies. In such cases, faecal waste is collected in a reservoir bag or pouch attached to a stoma, bypassing damaged or absent sections of the bowel.
Stoma formation may be temporary or permanent, allowing either the bowel to rest or a section of the bowel to be removed. The length of bowel documented in the patient’s notes should refer to the length of bowel remaining post-resection.
In all surgical procedures, appropriate pre- and post-operative management is vital to a patient’s recovery and the success of the intervention. Patients who have had a stoma created have an additional set of pharmaceutical care issues.
Pharmacists may also encounter patients with stomas on non-surgical wards and therefore need to consider certain issues when screening prescriptions and advising on medicines for these patients.
Underlying disease
Bowel cancer, Crohn’s disease and ulcerative colitis are the most common conditions that lead to bowel resection and stoma formation. Once a stoma has been formed patients will require a medication review to identify whether any treatments can be stopped.
In ulcerative colitis, a total colectomy is considered curative, and medicines to treat the condition can therefore be stopped. Crohn’s disease can recur following surgery so the extent of disease and surgery performed determines further treatment. Patients taking corticosteroids long term will require a reducing regimen if treatment is to be stopped.
Control of stoma output
The amount of faecal waste removed through the stoma is called the stoma output. Typical volumes are 400–800ml per day and should ideally not exceed 1,000ml. Controlling the volume of stoma output may require pharmacological intervention. Medicines that increase output (e.g., laxatives and prokinetics) should be stopped; and medicines that reduce stoma output (eg, those that decrease gut motility or reduce gastric secretions) may need to be prescribed. Stoma output can also be too low or absent (see Box 1).
Box 1. Increasing stoma output
In some patients, stoma output may be too low or absent. This can be caused by post-operative ileus following stoma formation — prohibiting the passage of gastric contents through the bowel. Certain drugs can also decrease gut motility, e.g., opioids and antimuscarinics. For patients affected, stoma output can be increased by:
- Prokinetic drugs taken before meals, e.g., metoclopramide (10mg three times a day), domperidone (10mg three times a day) or erythromycin (250mg three times a day);
- Enteral feeding via a nasogastric tube to stimulate the small bowel;
- Glycerol suppositories inserted into the stoma opening (providing the patient is constipated and faeces can be felt on internal examination of the stoma).
Antimotility drugs
Loperamide and codeine are opioid agonists that decrease gut motility thereby decreasing stoma output. They predominantly act on the μ-receptors of the bowel to reduce peristalsis and should be taken 30–60 minutes before meals and at bedtime. Loperamide is commonly used at off-label doses of up to 8mg four times a day and higher doses are sometimes needed[1]. If the desired response is not obtained with loperamide, codeine may be added to therapy. It is usually prescribed at doses similar to those used for analgesia (15–30mg four times a day, not exceeding 240mg in 24 hours). Tolerance and dependence issues may limit codeine use and patients should be monitored for signs of addiction.
Antisecretory drugs
Gastric acid secretions often increase after small bowel resection because of interference with negative feedback mechanisms that control the process. This can lead to increased stoma output. Reducing gastric acid secretions can therefore decrease stoma output. Proton pump inhibitors (PPIs) and somatostatin analogues are often used for this purpose.
PPIs block the production of gastric acid. Omeprazole is the most commonly used PPI in this setting and high doses of 40mg twice a day are often needed. Because omeprazole is absorbed in the upper sections of the small intestine, patients who have had extensive small bowel surgery may not respond fully to the drug.
Octreotide and lanreotide are analogues of the hormone somatostatin, which inhibits gastrin to reduce gastric acid production. They can be prescribed off-label for stoma patients to reduce gastric and intestinal secretions. Octreotide is used more often than lanreotide; suitable doses of octreotideare 50–100mg three times a day by subcutaneous injection.
Fluid replacement
Fluid replacement in patients with a high stoma output is often managed incorrectly. Excessive intake of hypotonic fluids (such as water, tea and coffee) in response to an increased stoma output can lead to sodium depletion and dehydration[1]. Patients with a high output should to limit their intake of hypotonic fluids to 500ml per day and make up their total fluid intake of 1,500ml per day with an oral rehydration solution (see Box 2).
Box 2. Oral rehydration
Oral rehydration solutions used for patients who have high stoma output include St Mark’s solution and Dioralyte “double strength” solution (see below). Both are made up to 1L with tap water, freshly prepared every morning and stored in the fridge. Patients drink the solution through the course of the day.
St Mark’s solution
Contains glucose 20g, sodium bicarbonate 2.5g and sodium chloride 3.5g. Each litre of solution provides:
- Sodium 90mmol
- Chloride 60mmol
- Glucose 111mmol
- Bicarbonate 30mmol
Dioralyte “double strength” solution
Contains 10 sachets of Dioralyte. Each litre of solution provides:
- Sodium 120mmol
- Potassium 40mmol
- Chloride 120mmol
- Glucose 180mmol
- Citrate 20mmol
Nutritional considerations
Bowel conditions, such as ulcerative colitis and Crohn’s disease, can reduce a patient’s absorption of nutrients substantially. Following stoma formation the patient could be at risk of refeeding syndrome when feeds are reintroduced. These patients should be assessed and managed appropriately to prevent this potentially fatal complication. Some of the main nutritional deficiencies that can affect patients with a stoma are discussed below and the National Institute for Health and Clinical Excellence clinical guideline “Nutritional support in adults” [2] contains more detail on assessment criteria and treatment options for malnourished patients.
Vitamin B deficiency
Thiamine (vitamin B1) deficiency should be considered in malnourished patients at risk of refeeding syndrome. Thiamine is an essential co-enzyme in carbohydrate metabolism[2] and deficiency can lead to dangerous electrolyte disturbances when carbohydrates are reintroduced. In high-risk patients this can be prevented by commencing feeding slowly and replenishing thiamine stores at the same time. Intravenous high-dose thiamine is given in the form of Pabrinex (combination B vitamins) at a dose of one pair of vials daily. When an oral route is available, thiamine, multivitamins and vitamin B compound strong may be prescribed.2Following 10 days of treatment thiamine stores should be sufficiently replenished —reducing the risk of refeeding syndrome.
Hypomagnesaemia
Increased chelation of magnesium with unabsorbed fatty acids in the bowel lumen and increased losses via the stoma can lead to hypomagnesaemia. Magnesium is an important co-factor for enzymatic reactions and it helps maintain normal central nervous system activity. It is also a co-factor for the sodium-potassium ATPase pump; therefore, if magnesium is low, potassium supplements will not be effective in treating hypokalaemia[1]. Fluid and sodium depletion in this patient group can often lead to hypokalaemia, which should be managed accordingly.
Oral magnesium supplements are available as unlicensed products and 10mmol of magnesium daily is usually sufficient to replenish levels. Diarrhoea, a common side effect of magnesium, is thought to occur less with magnesium-L-aspartate formulations; however patient tolerability can vary.
Low magnesium can be exacerbated by low phosphate levels, therefore phosphate should also be monitored and replaced if necessary.
Hypoalbuminaemia
Absorption of dietary proteins may be impaired as a result of the underlying bowel disease or the formation of a stoma. Albumin levels can fall because the body may prioritise the synthesis of acute phase proteins, such as C-reactive protein, over albumin. Serum albumin is used as a prognostic marker for the underlying disease rather than nutritional status.
Hypoalbuminaemia can result in increased plasma concentrations of highly protein-bound drugs, such as warfarin and phenytoin.
Pharmacokinetic issues
Several pharmacokinetic issues can arise from stoma formation and bowel resection. Pharmacists need to consider these when monitoring and advising on drug therapies.
Absorption
The use of modified-release or enteric-coated products should be reviewed. Such medicines are generally considered unsuitable, since the active ingredient may not be at the site of absorption long enough or may bypass it completely. Patients should be advised to check their stoma bags for whole capsules or tablets.
Use of prokinetics and medicines with laxative side effects may reduce the length of time available for absorption. Sorbitol is an excipient used widely in pharmaceutical preparations and has osmotic laxative properties; medicines containing sorbitol should therefore be avoided.
Drugs that need an acidic environment to be absorbed (e.g., levothyroxine) can be affected by an increase in pH from the use of PPIs. Monitoring response to therapy is necessary and doses may need to be increased.
Distribution
Dehydration caused by high stoma output can lower the volume of distribution of water-soluble drugs. The drugs most likely to be affected are those with a narrow therapeutic index, such as gentamicin or digoxin. In these instances, careful calculation of the loading dose and therapeutic drug monitoring are essential — as is surveillance for early signs of toxicity.
As mentioned above, hypoalbuminaemia can result in increased plasma concentrations of highly protein-bound drugs and such medicines should be monitored appropriately.
Metabolism
Reduced absorption and synthesis of proteins in chronically malnourished patients can affect drug metabolism. With less protein being broken down into amino acids, there are fewer amino acids available to form enzymes for drug metabolism. The processes that the body adopts to compensate for these changes are complex as is understanding the full effect of protein loss on drug metabolism.
Pharmacists should be vigilant in monitoring the response to therapy of any drug in patients with chronic protein deficiency. In-depth management of such patients is usually undertaken by specialist teams.
Excretion
Dehydration can lead to renal dysfunction in patients who have a high stoma output, and the clearance of some drugs could be reduced accordingly. Patients should be monitored appropriately for any changes in renal function.
Summary
When managing a patient with a colorectal stoma, clinicians should consider reviewing treatment regimens to identify any medicines treating the underlying bowel disease that can be stopped or changed. The volume of stoma output should be monitored and medicines prescribed if it is found to be too high or too low. Nutritional supplementation should be considered to avoid deficiencies caused by the structural changes to the bowel.
Acknowledgement
Thanks to Gareth Malson, clinical and medicines management pharmacist, and Gareth Nickless, lead pharmacist for education and training.
References
- Nightingale J, Woodward JM. Guidelines for management of patients with a short bowel. Gut 2006;55:iviv12.
- National Collaborating Centre for Acute Care. Nutrition support in adults: Oral nutrition support, enteral tube feeding and parenteral nutrition. February2006. www.nice.org.uk/nicemedia/live/10978/29981/29981.pdf (accessed October 2012).
