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People often experience some form of digestive distress after taking oral medications such as blood-pressure drugs, anticholinergics, opioids, antispasmodics, antacids, and antibiotics.
Some of these drugs hamper the nerve and muscle function in the large intestine, while others disrupt the gut flora.
This comes in the way of proper digestion and bowel movement, thus giving rise to constipation, diarrhea, acid reflux, intestinal gas, and such problems.
This article explores the truth behind the claim that antibiotics cause constipation by reviewing scientific work done on this topic.
What Is Constipation?
It can be defined by having any two of the following characteristics (at least 25% of the time):
- Straining during bowel movements
- Hard bowel movements
- Incomplete evacuations
- Sensation of obstruction or blockage
- Fewer than three bowel movements per week
This definition comes from a panel of experts and is referred to as the Rome IV criteria. (3)
Primary Vs. Secondary Constipation
Secondary constipation is due to medications or an underlying disease. Inflammatory diseases, infectious diseases of the bowel, and irritable bowel syndrome are common causes of secondary constipation.
Neurologic disorders, metabolic disorders, and endocrine disorders such as diabetes all have an increased incidence of constipation.
If your constipation is accompanied by pain, weight loss, or bloody stools or it does not resolve after 1–2 weeks, seek medical advice.
What Are Antibiotics?
Antibiotics are a class of drugs that kill bacteria or curb their growth. These chemicals target the parts of bacteria involved in their growth and survival.
For example, an antibiotic may work by inhibiting the formation of the bacterial cell wall and proteins or by altering the bacterial cell membrane.
Some antibiotics arrest the growth of bacteria (bacteriostatic), and other antibiotics directly kill the bacteria (bactericidal).
Antibiotics can be broadly classified into two categories:
- Broad-spectrum antibiotics: These antibiotics target a wide variety of bacteria at once. They may also affect those bacteria that are beneficial to health.
- Narrow-spectrum antibiotics: These antibiotics attack only some bacterial species and are highly specialized.
Do Antibiotics Cause Constipation?
Broad-spectrum antibiotics that are used to kill pathogenic bacteria can also affect the commensal bacteria living in the gut. This disturbs the composition of the gut flora.
As a result of the imbalance, you may suffer from gas and diarrhea. Therefore, antibiotics commonly cause diarrhea as a side effect. They may rarely cause constipation.
Other side effects of antibiotics that affect the digestive system include:
Medications That Can Cause Constipation
Constipation can result from many reasons. It is often a side effect of certain medicinal drugs, which include:
1. Calcium-channel blockers
Diltiazem (Cardizem) and amlodipine (Norvasc) are examples. These drugs are used to lower blood pressure by relaxing the smooth muscles of blood vessels. They may also relax the gut muscles, thus causing constipation.
Anticholinergics are used to treat a variety of conditions, including:
- Urinary incontinence (loss of bladder control) – oxybutynin (Ditropan)
- Allergies – diphenhydramine (Benadryl)
- Depression – antidepressants
Acetylcholine, a neurotransmitter responsible for inducing muscle movement, is blocked by anticholinergics. Loss of movement of the intestinal muscles due to the ineffectiveness of acetylcholine can cause constipation. (4)
Opioids are used for pain relief and include morphine and codeine. Also known as narcotics, these drugs bind to pain receptors and prevent the dispersion of pain signals.
These drugs can stimulate an increase in the absorption of water by the colon, causing constipation.
Antispasmodics, such as dicyclomine, are used to suppress muscle spasms. These medicines work by reducing the frequency of muscle contractions.
Reduced muscle contractility may affect the peristaltic movement of waste material in the colon and induce constipation.
Antacids contain aluminum, which affects the muscular activity of the gut, resulting in constipation.
Cholestyramine is used to reduce cholesterol levels in the blood. By binding to bile acids, it affects water absorption from the food. As a result, the stool formed is dry and hard to pass.
Consult your clinical practitioner before using any of these medications.
Studies Supporting the Link Between Medications and Constipation
Several studies have suggested that some medications can cause constipation:
- The association of constipation with the increasing number of drugs used by the elderly was demonstrated in a population-based study conducted in 2018. (5)
- A 2003 study, published in the Journal of Neurology, Neurosurgery, and Psychiatry, reviewed the incidence of constipation in patients with neurological diseases. Findings indicated that a variety of drugs could, alone or in combination, cause or worsen constipation. (6)
- A case study in 2005 reported gastrointestinal complications in two patients taking antidepressant drugs. The patients showed symptoms associated with the action of anticholinergic medicines, including dryness in the mouth, blurred vision, tremors, and constipation. (7)
- A meta-analysis conducted in 2011 found that patients taking anticholinergics for an overactive bladder were prone to constipation. (8)
- A review study in 2016 found constipation to be one of the most frequent adverse side effects of anticholinergics in the elderly. (9)
- Constipation was found to be commonly associated with prolonged use of opioids, according to a study conducted in 2016. (10)
Individuals at High Risk of Constipation
- Older adults are more susceptible to constipation, which occurs as a side effect of medications. This is primarily due to the decreased motility with aging.
- Infants become highly susceptible to constipation if they are given poor-quality milk.
- Constipation may also occur in people with a lack or imbalance of beneficial gut bacteria, a condition medically known as dysbacteriosis.
- Pregnant women are at a high risk of constipation, primarily due to their high levels of progesterone. The use of certain medications by pregnant women can exacerbate this.
Expert Answers (Q&A)
Answered by Dr. Rajan Menghani, DO
Antibiotics can have a wide variety of side effects, ranging from skin rash, nausea, and upset stomach to serious issues such as hearing loss.
In rare cases, life-threatening conditions such as Stevens-Johnson syndrome (which may cause a fever and a skin rash with blisters) can result.
Ask your doctor about the side effects that you may expect when taking antibiotics, and make sure to notify your doctor if they become bothersome.
If you experience wheezing, difficulty breathing, or swelling in your tongue, lips, or throat, then seek medical attention or call 911 immediately as these symptoms may indicate a life-threatening allergic reaction called anaphylaxis.
It is also important to note that taking unnecessary antibiotics can increase the risk of bacterial resistance. This means that the next time this same antibiotic is given to you, it may not be effective, and another antibiotic may be necessary.
Therefore, only take antibiotics that are prescribed by your doctor, and do not self-medicate with antibiotics just because they are sitting in your medicine cabinet.
A variety of drugs may cause constipation, but some of the most common culprits are opioid medicines, which are sometimes prescribed for severe pain.
Some antibiotics may affect how oral contraceptives are metabolized in the body. They can decrease the efficacy of contraceptives and may increase your risk of becoming pregnant if you are sexually active.
It is, therefore, necessary to let your doctors know of all contraceptives, medications, and supplements you are taking so that they may make the right decision and give you the necessary instructions.
Some people, especially children, may be sensitive to dairy products and may develop constipation after consuming them.
A study done in Spain showed that drinking cow’s milk might cause constipation in children. (11) However, because everyone is different, not everyone will have the same reaction to a specific food.
If you do develop constipation while on a certain antibiotic, your doctor may recommend a different antibiotic or may advise you to include adequate fiber and water in your diet.
Several antibiotics are considered safe for children. However, there are some notable exceptions, including tetracyclines and fluoroquinolones.
Tetracyclines (such as doxycycline and tetracycline) should not be given to children under 8 years old because they can cause permanent discoloration of the teeth.
It is best to avoid giving fluoroquinolones (such as ciprofloxacin and levofloxacin) to anyone under the age of 18 years because they can cause tendinitis or rupture of the tendons.
Make sure you address all of your concerns with your doctors and work with them to determine which antibiotics, if necessary, are right for you.
When you visit your doctor, be prepared to answer questions regarding health issues you have had, allergies, and medicines and supplements you are taking. Also, inform your doctor if you may be pregnant, as some antibiotics may potentially harm the baby.
Your doctor may then want to perform a pregnancy test. This information is essential for the doctor to determine which antibiotic, if necessary, is right for you.
It is important to take antibiotics exactly as prescribed and finish the entire course so that the infection is properly treated and the bacteria do not survive and become resistant to the antibiotic.
Constipation is a very common problem. It is usually a side effect of medications and can be easily managed through self-care. If the problem does not subside, seek medical help.
Chronic constipation can give rise to complications that are difficult to treat. Although antibiotics occasionally are associated with constipation, some of the more common side effects associated with antibiotics seem to be diarrhea and gas.