Activated charcoal - adverse interactions with other medications
The adsorptive properties of activated charcoal can interfere with the intended absorption of certain drug compounds in the gastrointestinal tract, rendering them ineffective.
Activated charcoal inhibits the gastrointestinal absorption of toxic substances by adsorbing these itself, however, multiple doses can sometimes interfere with the enteroenteric (the secretion of substances back into the intestines), enterohepatic (circulation of substance and biliary salts from the liver to the intestine), and enterogastric (gastric motility) circulation of certain medications. This is due to the fact that activated charcoal can also sometimes adsorb medication that remains unabsorbed in the gut at the time of its administration.
The following medications would require close monitoring if taken around the same time as activated charcoal:
- Acetylcysteine: This medication may be used to help loosen an accumulation of mucus lodged in the airways as a result of conditions such as bronchitis, pneumonia, cystic fibrosis or emphysema. It can also be used as a treatment for paracetamol (acetaminophen) overdose. Activated charcoal may decrease the medication’s effects in the treatment of mucus build-up. In the case of a paracetamol overdose, however, it has not been conclusively proven that activated charcoal interferes with the medication thus preventing effective treatment.
- Citalopram: An antidepressant, this medication is classed as a selective serotonin reuptake inhibitor (SSRI). The medication may be prescribed to patients diagnosed with depression. Activated charcoal in the system may reduce the beneficial effects of the medication considerably (by decreasing its absorption in the body), rendering it ineffective. This is often referred to as ‘pharmacodynamic antagonism’.
- Digoxin (oral): Most often prescribed for heart conditions like atrial flutter, atrial fibrillation or heart failure, the beneficial effects of this medication can be hampered by the administration of activated charcoal. Activated charcoal (taken orally) interferes with the absorption of this medication in the gastrointestinal tract, decreasing the dosage required for effective treatment.
- Dyphylline: This medication is prescribed in the treatment of respiratory conditions such as bronchitis, asthma or cardiac dyspnoea (cardiac disease). The medication is a xanthine derivative with a bronchodilator which has vasodilator effects (i.e. it opens the bronchial tubes of the lungs and blood vessels, helping the personal taking it to breathe more easily). Activated charcoal disrupts gastrointestinal absorption, decreasing the levels of the medication in the system needed for effective treatment.
- Methotrexate (formerly known as amethopterin): Most often prescribed as a chemotherapy agent (for the treatment of cancer) or as an immune system suppressant (often used to treat autoimmune conditions). It has also been prescribed in the treatment of medical abortions and ectopic pregnancies. Activated charcoal interferes with absorption of this medication, resulting in impaired systemic circulation and ineffectiveness.
- Theophylline (oral): This medication is typically prescribed for the treatment of COPD (chronic obstructive pulmonary disease) or asthmatic conditions. The levels of this medication in the body can be reduced by orally administered activated charcoal as absorption in the gastrointestinal tract is prevented.
The following medications would require some monitoring if taken around the same time as activated charcoal (although are generally subject to minor interference effects):
- Acarbose (oral): This medication is used in the treatment of diabetes type 2, and sometimes pre-diabetes. Levels of the medication may be decreased through absorption interference in the gastrointestinal tract when activated charcoal is taken orally.
- Leflunomide (oral): This medication is classed as an immunosuppressive condition-modifying anti-rheumatic drug. It is commonly prescribed for the treatment of moderate to severe active rheumatoid or psoriatic arthritis. Gastrointestinal absorption is disrupted by activated charcoal, reducing levels of the medication in the system and thereby preventing its intended effect.
- Miglitol (oral): This medication is prescribed to treat diabetic patients, and effectively works by inhibiting the breakdown of complex carbohydrates into glucose. Activated charcoal hinders gastrointestinal absorption, which decreases medication levels in the system and thus hampers this beneficial process.
*Note: Adverse effects (absorption inhibition or interference) caused by orally administered activated charcoal may be alleviated when taking orally administered medications by allowing at least an hour gap in between the two therapies. (2)
What about using activated charcoal at the same time as the contraceptive pill?
Studies have been done to determine if any interference applies to the simultaneous use of activated charcoal with birth control pills. One study has been able to identify compromised effectiveness of oral contraceptives when activated charcoal is taken mid-way through a pill cycle. (3) Alternative methods of birth control are advised as a precaution if unwanted pregnancies are to be avoided.
Possible side-effects of activated charcoal
Relatively common activated charcoal side effects
- Black stool (faeces)
- Staining / dental discolouration – the black pigment can result in black discolouration of the mouth, tongue or teeth
Rare activated charcoal side effects
- Abdominal pain or swelling (distention)
- Intestinal tract difficulties (slowing functionality or causing a blockage)
- Regurgitation (vomiting) into the lungs or aspiration pneumonitis (this can be life-threatening if respiratory function is severely compromised)
A medical professional will respond swiftly if any of the following reactions occur: (4)
- Signs of a potential allergy – itching, swelling (especially in the facial area, mouth throat or hands), hives (urticaria), tingling sensations (especially in the mouth or throat), tightness in the chest or breathing difficulties.
- Severe (new or worsened) constipation, diarrhoea, nausea, vomiting or abdominal pain.
- Changes in urine / urination (e.g. dark urine or infrequent urination)
If a person is treated with activated charcoal in a hospital environment in the case of poisoning or chemical overdose, medical personnel will keep a watchful eye for potential side-effects. Those who experienced persistent vomiting will be monitored for any potential changes in their mental state. Patients will also likely be monitored and checked periodically for any signs of abdominal obstructions or even peritonitis (abdominal inflammation due to the rupturing of an abdominal organ).
Activated charcoal is not known to cause any significant toxicity in the body. It is believed that it is not systemically absorbed and does not interfere with the transport of oxygen and carbon dioxide to and from the lungs. Respiratory difficulties more typically occur as a result of complications like severe aspiration or vomiting which result in airway obstructions than from activated charcoal itself.
Activated charcoal warnings and contraindications
Activated charcoal is not recommended for the following physical problems:
- Intestinal obstructions (blockages) or known problems with slow movement of food through the digestive tract – this can sometimes be caused by conditions such as Crohn’s disease, irritable bowel syndrome or diverticulitis.
- Airways which are unprotected - Airways must be clear in case vomiting occurs as a side-effect of activated charcoal intake. Should a patient not be sufficiently conscious, if necessary, intubation of the airways can help to provide protection in a hospital environment.
- Injury due to the ingestion of corrosive or abrasive substances (i.e. caustic ingestions).
Activated charcoal should also not be considered in the following instances:
- If it is determined that use of activated charcoal is likely to induce severe aspiration (vomiting).
- If it is identified that a patient is at risk of gastrointestinal perforation or haemorrhage (peritonitis).
- If an endoscopy procedure is necessary – activated charcoal may interfere with visualisation clarity.
- If it is determined that a patient has ingested substances known to be ineffectively treated by activated charcoal, such as acids, alkalis, metals, alcohols or electrolytes.
Use of activated charcoal does come with the following warnings and cautions:
- Activated charcoal can induce vomiting (especially if the substance is ingested / consumed rapidly or is mixed with sorbitol).
- Those with impaired or decreased peristalsis function (i.e. issues with the wave-like contraction and relaxation of the muscles that assist in moving food from the oesophagus through the digestive tract)
- Caution is advised when using activated charcoal with substances such as Ipecac / syrup of Ipecac (often used to induce rapid / forceful vomiting in poisoning situations) – effectiveness of Ipecac may be decreased as the substance binds to the syrup.
- Use with sorbitol (or other cathartics like magnesium sulfate) may increase electrolyte irregularities and thus should not be administered by anyone other than a medical professional who can monitor and treat any abnormal effects that may arise. Those with a fructose intolerance (or allergy) or who show signs of dehydration should also not use activated charcoal mixed with sorbitol.
- Activated charcoal in tablet or capsule form should not be used for poisoning or overdose treatment. If poisoning is suspected, seek medical assistance.
- Women who are pregnant or breastfeeding – absolute safety has not been determined, although significant exposure to activated charcoal is not expected to directly affect an unborn or nursing baby. This is because oral administration of the substance is processed via the gastrointestinal tract and not directly through the circulatory system which reaches more of the body’s tissues including other major organs and bloodstream. It is best, however, to consult a medical doctor before using activated charcoal for any alternative reason, even if for a short period. If poisoning is suspected, medical professionals in a clinical setting may still administer treatment to a woman who is pregnant or breastfeeding.
- Activated charcoal should never be taken with alcohol as this can inhibit its adsorptive properties and render the substance ineffective (particularly in the case of overdose or poisoning).
For suspected overdoses and poisonings, it is advisable not to try and treat an individual without the express consent or guidance of a medical professional. If not used at the most appropriate dosages, activated charcoal can result in unwanted side-effects. Children who have or may have consumed a potentially toxic substance should always be attended to by a medical professional as soon as possible. No person should ever attempt to administer activated charcoal to an individual who is unconscious.
Can certain foods affect the adsorptive capacity of activated charcoal?
Foodstuffs such as milk, ice cream and even sorbet are capable of interfering with the adsorption capacity of activated charcoal in the stomach. One in vitro study assessed adsorption capacity using 4 different types of ice cream and paracetamol (acetaminophen) as a way to demonstrate such a possibility in patients who may be admitted for poisoning treatment. Activated charcoal and paracetamol were mixed with the ice creams before being incubated for about 1 hour. The adsorption capacity was shown to be reduced considerably (which varied according to the ice cream type used) in the grouping that used the ice cream. This study determined that even with reduced adsorptive capacity, activated charcoal may still be a useful form of treatment in the case of poisoning or overdose. (5)
2. MyHealth. 24 October 2016. Activated Charcoal: http://www.myhealth.gov.my/en/activated-charcoal/ [Accessed 25.04.2018]
3. Oxford Academic - Human Reproduction (Volume 16, Issue 1). January 2001. Charcoal treatment and risk of escape ovulation in oral contraceptive users: https://academic.oup.com/humrep/article/16/1/76/3113914/ [Accessed 25.04.2018]
4. PubMedHealth. May 2018. Activated Charcoal (By Mouth): https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0008816/?report=details [Accessed 01.05.2018]
5. PubMed- US National Library of Medicine National Institutes of Health. November 2003. The effect of food and ice cream on the adsorption capacity of paracetamol to high surface activated charcoal: in vitro studies: https://www.ncbi.nlm.nih.gov/pubmed/14629735 [Accessed 25.04.2018]