The side effects from activated charcoal, contained in charcoal tablets, include black stool and constipation. It can also cause the intestinal tract to slow or become completely blocked, dehydration and regurgitation into the respiratory system.
Activated charcoal is useful as a medicine to bind to substances, preventing them from being absorbed into the body. It is commonly used in some kinds of poisoning. Because it binds effectively, it has a slowing effect on the gastrointestinal system. People with intestinal blockage should not take charcoal tablets unless under the supervision of a medical provider. Generally, charcoal should not be taken with alcohol as it decreases the effectiveness of the charcoal. Likewise, medication and syrup of ipecac are incompatible with charcoal, as their effectiveness is lessened by the binding interaction of the latter.