Oral activated charcoal (OAC) can delay development of hyperphosphatemia and vascular calcifications in patients with stage 3–4 chronic kidney disease (CKD), according to the findings from a 2-phase trial published in the Journal of Nephrology.

In the first phasel, Zunsong Wang, MD, of Shandong University, and colleagues randomly assigned 97 Chinese patients to OAC (0.6–1.2 g thrice daily with food) or placebo. Over 12 months, hyperphosphatemia (defined as a serum phosphorus levels greater than 5.8 mg/dL), developed in a significantly smaller proportion of patients who took OAC compared with  placebo recipients: 28.6% vs. 79.3%.

In the second phase, investigators randomly allocated OAC, lanthanum carbonate, or calcium carbonate to patients with hyperphosphatemia. Results from coronary artery multidetector computed tomography showed that patients treated with lanthanum carbonate and OAC had significantly lower mean coronary calcification scores than those treated with calcium carbonate after 24 months: 431.4 vs 525.5 vs 688.1, respectively. The team found no significant score differences between the OAC and lanthanum carbonate groups.

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The most common adverse events with OAC were gastrointestinal disorders, such as constipation and abdominal distention or pain.

“Activated charcoal has a strong adsorption force, with various pore sizes at the surface. After ingestion, it rapidly spreads in the intestine, strongly absorbing small molecules and toxic substances. It has a role in reducing blood phosphorus,” Dr Wang and his colleagues wrote.

Since the study’s sample size was small, larger studies are needed to confirm the findings.


Gao Y, Wang G, Li Y, et al. Effects of oral activated charcoal on hyperphosphatemia and vascular calcification in Chinese patients with stage 3–4 chronic kidney disease. J Nephrol. 2018; DOI:10.1007/s40620-018-00571-1