Lactose in medicines
Lactose is widely used as an excipient in pharmaceutical manufacturing.
Although anecdotal reports of drug-induced lactose intolerance exist, when used as an excipient the lactose content in most medicines is too small to cause problems. Daily lactose exposure from medicines is unlikely to exceed 2g per day. Whereas the threshold for lactose intolerance symptoms is approximately 12g (equivalent to 250ml of milk).
Therefore, it is unlikely that severe gastrointestinal (GI) symptoms will be due to lactose in medicines, especially in adults without a diagnosis of severe intolerance.
Checking if lactose is present
If an adult has severe lactose intolerance, you may need to limit lactose exposure from medicines.
The Summary of Product Characteristics (SPC) for a medicine can be used to check if lactose is present as an excipient. However, it is usually necessary to contact the manufacturer to determine the exact amount of lactose in a medicine. The amount may vary by manufacturer, product, formulation, or strength.
To identify lactose-free products follow advice in our article below.
Searching for presence or absence of an excipient in medicines
Lactose intolerance
Lactose intolerance is caused by an absence or deficiency of the enzyme lactase (hypolactasia). This enzyme breaks down lactose, a natural sugar found in animal milk, in the small bowel.
If undigested lactose reaches the colon, it draws in fluid and is fermented by enteric bacteria, which can cause unwanted effects.
Symptoms
Symptoms associated with lactase deficiency are variable. They depend on the amount of lactose ingested, a person’s ability to digest lactose and the amount and type of colonic bacteria. Some people will be symptom free, whereas others may experience painful and persistent GI symptoms, such as abdominal bloating, wind, diarrhoea, nausea and abdominal cramps.
Most adults with lactose intolerance do not need a severely restricted or lactose-free diet.
Types of lactose intolerance
There are several types of lactose intolerance or lactase deficiency (hypolactasia) and the condition may be temporary or permanent.
Primary
This is the most common form and occurs as affected individuals begin to produce less lactase as they age. It usually starts at around 2 years of age, but symptoms may not occur until years later, if at all.
Secondary
This may occur following injury to the small bowel. Injuries may result from infections (such as gastroenteritis) or diseases that impair lactase production (such as inflammatory bowel disease).
Other
Less common types of lactose intolerance are congenital lactase deficiency or developmental lactase deficiency.
Milk Allergy
Do not confuse lactose intolerance with cow’s milk allergy. These are two different conditions with different management options.
Lactose intolerance is due to an enzyme deficiency, cow’s milk allergy is an immune response to proteins found in cow’s milk rather than an allergy. People with a cow’s milk allergy can receive medicines containing lactose.
Further resources
More detailed information on lactose intolerance is available from a variety of online sources. Examples include:
For healthcare professionals
- SPS - Understanding excipients in medicines
- BMJ Best Practice (may require log-in)
- Patient UK – Lactose intolerance for medical professionals
For members of the public
Update history
- Addition of section relating to cow's milk allergy. Steps to find lactose free products removed and referred to 'searching for presence or absence of an excipient' page. Title changed from 'Prescribing in lactose intolerance and how to identify lactose free medicines' to 'Assessing the clinical impact of lactose in medicines'.
- Full content review and page restructure.
- Published
- Minor grammatical and structural changes.