Charcoal repeat-dose

F. Repeat-dose activated charcoal. Repeated doses of activated charcoal (20-30 g or 0.5-1 g/kg every 2-3 hours) are given orally or via gastric tube. The presence of a slurry of activated charcoal throughout several meters of the intestinal lumen reduces blood concentrations by intermpting enterohep-atic or enteroenteric recirculation of the dmg or toxin, a mode of action quite distinct from simple adsorption of ingested but unabsorbed tablets. This technique is easy and noninvasive and has been shown to shorten the half-life of phenobarbital, theophylline, and several other dmgs (Table 1-41). However, it has not been shown in clinical trials to alter patient outcome. Caution Re-peat-dose charcoal may cause serious fluid and electrolyte disturbance secondary to large-volume diarrhea, especially if premixed charcoal-sorbitol suspensions are used. Also, It should not be used in patients with ileus or obstmction. 

Supportive care is important, especially in unconscious patients. If the airway is protected (gag reflex or cuffed endotracheal tube present), then activated charcoal can be given. Repeated doses of oral activated charcoal increase the rate of elimination of several tricyclic antidepressants, but may not influence outcome. 

Repeated dose of activated charcoal administered by oral route have been shown to enhance the non-renal elimination of carbamazepine, salicylates, phenobarbitone, phenytoin, digoxin, theophylline and meprobamate. In severe cases activated charcoal is to be administered via a nasogastric tube. 

General supportive care should be provided. Aggressive gut decontamination should be carried out using repeated doses of activated charcoal and whole bowel irrigation. Propranolol or other blockers (eg, esmolol) are useful antidotes for B-mediated hypotension and tachycardia. Phenobarbital is preferred over phenytoin for convulsions most anticonvulsants are ineffective. Hemodialysis is indicated for serum concentrations greater than 100 mg/L and for intractable seizures in patients with lower levels. 

Hantson P, Vandenplas O, Mahieu P, Wallemacq P, Hassoun A. Repeated doses of activated charcoal and... 

Charcoal does not bind iron, lithium, or potassium, and it binds alcohols and cyanide only poorly. It does not appear to be useful in poisoning due to corrosive mineral acids and alkali. Recent studies suggest that oral activated charcoal given alone may be just as effective as gut emptying followed by charcoal. Also, other studies have shown that repeated doses of oral activated charcoal may enhance systemic elimination of some drugs (including carbamazepine, dapsone, and theophylline) by a mechanism referred to as "gut dialysis."... 

Haemoperfusion is effective for phenobarbitone (> 100-150 mg/1, but repeat-dose activated charcoal by mouth appears to be as effective, see above) and other barbiturates, ethchlorvynol, glutethimide, meprobamate, methaqualone, theophylline, trichloroethanol derivatives. 

In pigs, repeated doses of activated charcoal reduced the half-life of intravenous digoxin significantly from 65 to 17 hours and increased the clearance from 2.3 to 7.1 ml/minute/kg (162). 

There is evidence of the efficacy of charcoal in healthy volunteers. In six adult volunteers repeated doses of activated charcoal significantly reduced the half-life of digoxin from 23 to 17 hours without a significant increase in clearance the half-life of digitoxin was also reduced from 110 to 51 hours, and this was accompanied by a... 

In another patient there was convincing evidence of a change in the digoxin half-hfe after repeated doses of activated charcoal (166). 

However, the best evidence of the usefulness of repeated oral doses of activated charcoal in cardiac glycoside poisoning comes from the results of a randomized, placebo-controlled study in 402 individuals who took overdoses of the seeds of the yellow oleander tree in Sri Lanka. Repeated doses of activated charcoal reduced mortahty from 8.0% to 2.5% (26). 

Thus, the use of repeated doses of activated charcoal in patients with digitahs toxicity is a cheap way of increasing the rate of cardiac glycoside clearance. 

A 14-year-old boy took about 21 g of procainamide and developed abdominal pain, weakness, blurred vision, dry mouth, pain on swallowing, and headache (59). His pupils were dilated, his skin dry and pale, and his mucous membranes dry. His blood pressure was 106/49 mmHg, his heart rate 91/minute. Following a tonic-clonic seizure his blood pressure was 125/57 mmHg and his heart rate 136/minute in sinus tachycardia. He became lethargic with slurred speech. He was given repeated doses of activated charcoal and made a full recovery. The serum procainamide and acecainide (A-acetylprocainamide) concentrations were 63 and 80 pg/ml respectively. 

Repeated doses of activated charcoal may enhance elimination. Serum electrolytes should be monitored in all serious exposures. Intravenous administration of sodium bicarbonate may decrease toxicity. Hypotension can be treated with fluids and vasopressors if needed. Ventricular dysrhythmias can be treated with class IB antiarrhythmics such as phenytoin or lido-caine. Persistent bradycardia and third-degree heart block are indications for insertion of a temporary pacemaker. Seizures can be treated with diazepam. If seizures are uncontrolled, phenobarbital or phenytoin can be administered. 

Acute overdoses of rifampin are rarely serious. Supportive care, gastric decontamination with activated charcoal for substantial recent ingestions are all that is usually necessary. Given the extensive enterohepatic circulation of rifampin, repeated doses of activated charcoal may enhance elimination however, the clinical utility of the procedure is questionable. Systemic toxicity associated with the chronic administration of rifampin is an indication to discontinue the drug. 

Pond SM, Olson KR, Osterloh JD, et al. Randomized smdy of the treatment of phenobarbital overdose with repeated doses of activated charcoal. JAMA 1984 251 3104-3108. 

The usual gastrointestinal decontamination procedures are followed, emesis, lavage and acfivafed charcoal, within the first few hours of ingestion. Repeated doses of activated charcoal may be useful as this substance has been shown to effectively bind thallium ions. 

Valproic acid Hemodialysis, repeat-dose charcoal... 

TABLE Ml. SOME DRUGS REMOVED BY REPEAT-DOSE ACTIVATED CHARCOAL ... 

D. Enhanced elimination. Dialysis and hemoperfusion are not effective. Repeat-dose charcoal has not been studied. Renal elimination of dextroamphetamine may be enhanced by acidification of the urine, but this is not recommended because of the risk of aggravating the nephrotoxicity of myoglobinuria. 

Dapsone undergoes enterohepatic recirculation and is mote rapidly eliminated with repeat-dose activate charcoal (see p 57). 

D. Enhanced elimination. Hemodialysis, hemoperfusion, peritoneal dialysis, and repeat-dose charcoal are not effective in removing anticholinergic agents. 

D. Enhanced elimination. Owing to extensive tissue and protein binding with a resulting large volume of distribution, dialysis and hemoperfusion are not effective. Although repeat-dose charcoal has been reported to accelerate tricyclic antidepressant elimination, the data are not convincing. 

Methotrexate AI+, D+, G++, H+, M++, N+, P+, R+ Peak serum level 1-2 hours after oral dose. Folinio aoid (leucovorin see p 460) is specific antidote. Hemopetfusion questionably effective. Urinary alkallnization and repeat dose charcoal may be helpful. 

---