h2.DESCRIPTION
h3.**Activated charcoal** is a form of carbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions.
Due to its high degree of microporosity, just one gram of activated carbon has a surface area in excess of 500 m².
h2.CLASSIFICATION
h3.Polimer-coated activated carbon is a process by which a porous carbon can be coated with a biocompatible polymer to give a smooth and permeable coat without blocking the pores. It is used in clinical practice as a haemoperfusion column containing activated charcoal coated with cellulose acetate.
h2.INDICATIONS
h3.Polimer-coated activated carbon is useful for treatment in overdose by one or more drugs, especially barbiturates.
*This is achieved with hemoperfusion, a treatment technique in which large volumes of the patient's blood are passed over an adsorbent substance, the polimer-coated activated carbon in order to remove toxic substances from the blood.
“_Fixed-bed activated charcoal cartridges were used for hemoperfusion in the treatment of 54 patients with overdose of one or more drugs, including barbiturate, glutethimide, ethchloryvnol, meprobamate, methyprylon, methaqualone, salicylate, and diazepam. The most dramatic improvement was noticed in patients with phenobarbitol intoxication; they were admitted in stage 3-4 coma and were either awake or arousable by verbal communication at the end of 1 1/2 to 3 1/2 hours of hemoperfusion. Other intoxications improved slowly and required longer duration of treatment. The clearance rates of the drugs with hemoperfusion were greater than those usually achieved with hemodialysis. The data demonstrate the efficacy and usefulness of charcoal hemoperfusion for the management of drug overdose._” Fixed-bed charcoal hemoperfusion. Treatment of drug overdose, Koffler et al., 1978, Link.
*It seems also to be useful by oral administration also in acceleration of the body clearance of Phenobarbital, but only if the administration is immediate.
“_The efficacy of administering a slurry of 100 g of activated charcoal (AC) via the gastric tube following lavage was assessed in 25 treated and 37 control patients presenting to the emergency room with chemical evidence of sedative-hypnotics or aspirin in the blood. Efficacy was evaluated as the ability of AC to prevent further absorption as determined by subsequent blood drug concentration changes. Although fewer patients in the AC group showed increased blood drug concentrations, the differences were not statistically significant. Comparison of the mean percent change in blood drug concentrations at various times following treatment produced similar results. Comparisons using subgroups of patients based on the individual drugs, the treatment delay time, and entering functional decompensation showed significant benefit from AC only in the less symptomatic patients. Comparing these results with other studies demonstrating the unequivocal efficacy of early (e.g., 30 min) treatment, it is concluded that the use of AC following lavage may often be too late to benefit most patients. The authors suggest that AC be given in the home, emergency vehicle, or immediately upon admission._” Assessment of the efficacy of activated charcoal following gastric lavage in acute drug emergencies, Comstock et al., 1982, Link.
“_We investigated the effect of multiple oral doses of activated charcoal on the pharmacokinetics of intravenously administered phenobarbital in a randomized crossover trial. Six healthy men volunteered to take 200 mg of phenobarbital sodium per 70 kg of body weight intravenously on two separate occasions. On one occasion, each subject received oral activated charcoal (180 g) in divided doses over three days after the infusion of phenobarbital. Serum levels of phenobarbital were measured in all subjects up to 90 hours after the infusion, and urinary excretion of phenobarbital was measured in two subjects 24 to 96 hours after the infusion. A pharmacokinetic analysis showed that the charcoal decreased the serum half-life of phenobarbital from 110±8 to 45±6 hours (S.E.M.) (P<0.01), increased the total body clearance of phenobarbital from 4.4±0.2 to 12.0±1.6 ml per kilogram per hour (P<0.01), and increased the nonrenal clearance from 52 to 80 per cent of the total body clearance. We conclude that oral administration of activated charcoal enhances the nonrenal clearance of phenobarbital._” Acceleration of the Body Clearance of Phenobarbital by Oral Activated Charcoal, Berg, Berlinger et al., N Engl J Med. 1982; 307:642–4.)
h2.MOLECULAR MECHANISM
h3.Activated charcoal is good at trapping chemicals and prevents their absorption, thanks to its bewildering adsorption surface: in fact a gram of activated carbon can have a surface area in excess of 500 m², with 1500 m² being readily achievable.
h2.SIDE EFFECTS
No side effects were reported, because the CA administered by the gastric tube isn't absorbed by the intestinal mucosa, neither the haemoperfusion column containing activated charcoal coated with cellulose acetate has any metabolic effects.
