Treatment of theophylline toxicity with oral activated charcoal

Systematic review on the use of activated charcoal for gastrointestinal decontamination following acute oral overdose

INTRODUCTION

The use of activated charcoal in poisoning remains both a pillar of modern toxicology and a source of debate. Following the publication of the joint position statements on the use of single-dose and multiple-dose activated charcoal by the American Academy of Clinical Toxicology and the European Association of Poison Centres and Clinical Toxicologists, the routine use of activated charcoal declined. Over subsequent years, many new pharmaceuticals became available in modified or alternative-release formulations and additional data on gastric emptying time in poisoning was published, challenging previous assumptions about absorption kinetics. The American Academy of Clinical Toxicology, the European Association of Poison Centres and Clinical Toxicologists and the Asia Pacific Association of Medical Toxicology founded the Clinical Toxicology Recommendations Collaborative to create a framework for evidence-based recommendations for the management of poisoned patients. The activated charcoal workgroup of the Clinical Toxicology Recommendations Collaborative was tasked with reviewing systematically the evidence pertaining to the use of activated charcoal in poisoning in order to update the previous recommendations.

OBJECTIVES

The main objective was: Does oral activated charcoal given to adults or children prevent toxicity or improve clinical outcome and survival of poisoned patients compared to those who do not receive charcoal?  Secondary objectives were to evaluate pharmacokinetic outcomes, the role of cathartics, and adverse events to charcoal administration. This systematic review summarizes the available evidence on the efficacy of activated charcoal.

METHODS

A medical librarian created a systematic search strategy for Medline (Ovid), subsequently translated for Embase (via Ovid), CINAHL (via EBSCO), BIOSIS Previews (via Ovid), Web of Science, Scopus, and the Cochrane Library/DARE. All databases were searched from inception to December 31, 2019. There were no language limitations.  One author screened all citations identified in the search based on predefined inclusion/exclusion criteria. Excluded citations were confirmed by an additional author and remaining articles were obtained in full text and evaluated by at least two authors for inclusion. All authors cross-referenced full-text articles to identify articles missed in the searches. Data from included articles were extracted by the authors on a standardized spreadsheet and two authors used the GRADE methodology to independently assess the quality and risk of bias of each included study.

RESULTS

From 22,950 titles originally identified, the final data set consisted of 296 human studies, 118 animal studies, and 145 in vitro studies. Also included were 71 human and two animal studies that reported adverse events. The quality was judged to have a Low or Very Low GRADE in 469 (83%) of the studies. Ninety studies were judged to be of Moderate or High GRADE. The higher GRADE studies reported on the following drugs: paracetamol (acetaminophen), phenobarbital, carbamazepine, cardiac glycosides (digoxin and oleander), ethanol, iron, salicylates, theophylline, tricyclic antidepressants, and valproate. Data on newer pharmaceuticals not reviewed in the previous American Academy of Clinical Toxicology/European Association of Poison Centres and Clinical Toxicologists statements such as quetiapine, olanzapine, citalopram, and Factor Xa inhibitors were included. No studies on the optimal dosing for either single-dose or multiple-dose activated charcoal were found. In the reviewed clinical data, the time of administration of the first dose of charcoal was beyond one hour in 97% (n = 1006 individuals), beyond two hours in 36% (n = 491 individuals), and beyond 12 h in 4% (n = 43 individuals) whereas the timing of the first dose in controlled studies was within one hour of ingestion in 48% (n = 2359 individuals) and beyond two hours in 36% (n = 484) of individuals.

CONCLUSIONS

This systematic review found heterogenous data. The higher GRADE data was focused on a few select poisonings, while studies that addressed patients with unknown and or mixed ingestions were hampered by low rates of clinically meaningful toxicity or death.  Despite these limitations, they reported a benefit of activated charcoal beyond one hour in many clinical scenarios.

Cardiotoxicodynamics: Toxicity of Cardiovascular Xenobiotics

Maintaining adequate tissue perfusion depends on a variety of factors, all of which can be influenced by xenobiotics (substances foreign to the body, including pharmaceuticals, chemicals, and natural compounds). Volume status, systemic vascular resistance, myocardial contractility, and cardiac rhythm all play a significant role in ensuring hemodynamic stability and proper cardiovascular function. Direct effects on the nervous system, the vasculature, or the heart itself as well as indirect metabolic effects may play a significant role in the development of cardiotoxicity. This article is dedicated to discussion of the disruption of cardiovascular physiology by xenobiotics.

Intermittent haemodialysis and sustained low-efficiency dialysis (SLED) for acute theophylline toxicity

INTRODUCTION

Theophylline overdose can result in significant cardiovascular and neurologic toxicity and is potentially fatal. Clearance of theophylline can be enhanced by the administration of multiple-dose activated charcoal (MDAC) and extracorporeal elimination techniques. We report a case of severe theophylline toxicity initially treated with MDAC and intermittent haemodialysis. Subsequent to this, sustained low-efficiency dialysis (SLED) was undertaken. This is a prolonged renal replacement therapy that uses blood and dialysate flow rates between those of intermittent haemodialysis and continuous renal replacement therapy.

CASE REPORT

A 61-year-old man presented following ingestion of 24 g of theophylline SR (300 mg/kg), 240 mg of diazepam and 2 g of gabapentin. He required intubation and developed a supraventricular tachycardia treated with esmolol, but suffered no seizures. Serum theophylline concentration peaked at 636 μmol/L (55-110) at 9.5 h post-ingestion. Intermittent haemodialysis was performed for 4 h and resulted in a theophylline extraction ratio of 0.57 with elimination half-life of 2.3 h. SLED was subsequently performed on two occasions for 7 h. Theophylline extraction ratio ranged from 0.46 (half-life 5.3 h during the first cycle) to 0.61 (half-life 10.6 h during the second cycle). After cessation of SLED, elimination half-life was 26 h. The patient made an uneventful recovery.

DISCUSSION

Intermittent haemodialysis is the current recommended extracorporeal technique for enhancing theophylline elimination in the absence of charcoal haemoperfusion. However, SLED produced similar apparent extraction ratios with longer associated elimination half-life for theophylline than for intermittent haemodialysis. SLED is undertaken by intensive care unit (ICU) staff and may be a useful extracorporeal elimination technique in cases where access to intermittent haemodialysis, requiring specialist dialysis nursing staff, is limited or may be delayed.

Extracorporeal treatment for theophylline poisoning: systematic review and recommendations from the EXTRIP workgroup

BACKGROUND

The Extracorporeal Treatments in Poisoning workgroup was created to provide evidence-based recommendations on the use of extracorporeal treatments (ECTRs) in poisoning. Here, the workgroup presents its systematic review and recommendations for theophylline.

METHODS

After a systematic review of the literature, a subgroup reviewed articles, extracted data, summarized findings, and proposed structured voting statements following a pre-determined format. A two-round modified Delphi method was chosen to reach a consensus on voting statements and the RAND/UCLA Appropriateness Method was used to quantify disagreement. Anonymous votes were compiled, returned, and discussed. A second vote determined the final recommendations.

RESULTS

141 articles were included: 6 in vitro studies, 4 animal studies, 101 case reports/case series, 7 descriptive cohorts, 4 observational studies, and 19 pharmacokinetic studies, yielding a low-to-very-low quality of evidence for all recommendations. Data on 143 patients were reviewed, including 10 deaths. The workgroup concluded that theophylline is dialyzable (level of evidence = A) and made the following recommendations: ECTR is recommended in severe theophylline poisoning (1C). Specific recommendations for ECTR include a theophylline concentration [theophylline] > 100 mg/L (555 μmol/L) in acute exposure (1C), the presence of seizures (1D), life-threatening dysrhythmias (1D) or shock (1D), a rising [theophylline] despite optimal therapy (1D), and clinical deterioration despite optimal care (1D). In chronic poisoning, ECTR is suggested if [theophylline] > 60 mg/L (333 μmol/L) (2D) or if the [theophylline] > 50 mg/L (278 μmol/L) and the patient is either less than 6 months of age or older than 60 years of age (2D). ECTR is also suggested if gastrointestinal decontamination cannot be administered (2D). ECTR should be continued until clinical improvement is apparent or the [theophylline] is < 15 mg/L (83 μmol/L) (1D). Following the cessation of ECTR, patients should be closely monitored. Intermittent hemodialysis is the preferred method of ECTR (1C). If intermittent hemodialysis is unavailable, hemoperfusion (1C) or continuous renal replacement therapies may be considered (3D). Exchange transfusion is an adequate alternative to hemodialysis in neonates (2D). Multi-dose activated charcoal should be continued during ECTR (1D).

CONCLUSION

Theophylline poisoning is amenable to ECTRs. The workgroup recommended extracorporeal removal in the case of severe theophylline poisoning.

Position statement and practice guidelines on the use of multi-dose activated charcoal in the treatment of acute poisoning. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists

In preparing this Position Statement, all relevant scientific literature was identified and reviewed critically by acknowledged experts using agreed criteria. Well-conducted clinical and experimental studies were given precedence over anecdotal case reports and abstracts were not usually considered. A draft Position Statement was then produced and subjected to detailed peer review by an international group of clinical toxicologists chosen by the American Academy of Clinical Toxicology and the European Association of Poisons Centres and Clinical Toxicologists. The Position Statement went through multiple drafts before being approved by the Boards of the two societies. The Position Statement includes a summary statement for ease of use and is supported by detailed documentation which describes the scientific evidence on which the Statement is based. Although many studies in animals and volunteers have demonstrated that multiple-dose activated charcoal increases drug elimination significantly, this therapy has not yet been shown in a controlled study in poisoned patients to reduce morbidity and mortality. Further studies are required to establish its role and the optimal dosage regimen of charcoal to be administered. Based on experimental and clinical studies, multiple-dose activated charcoal should be considered only if a patient has ingested a life-threatening amount of carbamazepine, dapsone, phenobarbital, quinine, or theophylline. With all of these drugs there are data to confirm enhanced elimination, though no controlled studies have demonstrated clinical benefit. Although volunteer studies have demonstrated that multiple-dose activated charcoal increases the elimination of amitriptyline, dextropropoxyphene, digitoxin, digoxin, disopyramide, nadolol, phenylbutazone, phenytoin, piroxicam, and sotalol, there are insufficient clinical data to support or exclude the use of this therapy. The use of multiple-dose charcoal in salicylate poisoning is controversial. One animal study and 2 of 4 volunteer studies did not demonstrate increased salicylate clearance with multiple-dose charcoal therapy. Data in poisoned patients are insufficient presently to recommend the use of multiple-dose charcoal therapy for salicylate poisoning. Multiple-dose activated charcoal did not increase the elimination of astemizole, chlorpropamide, doxepin, imipramine, meprobamate, methotrexate, phenytoin, sodium valproate, tobramycin, and vancomycin in experimental and/or clinical studies. Unless a patient has an intact or protected airway, the administration of multiple-dose activated charcoal is contraindicated. It should not be used in the presence of an intestinal obstruction. The need for concurrent administration of cathartics remains unproven and is not recommended. In particular, cathartics should not be administered to young children because of the propensity of laxatives to cause fluid and electrolyte imbalance. In conclusion, based on experimental and clinical studies, multiple-dose activated charcoal should be considered only if a patient has ingested a life-threatening amount of carbamazepine, dapsone, phenobarbital, quinine, or theophylline.

Prevention of drug absorption in simulated theophylline overdose

1. The effects of emesis, gastric lavage and oral activated charcoal on theophylline absorption were compared in healthy volunteers. 2. One of four regimes (ipecacuanha-induced emesis, gastric lavage, oral activated charcoal and no treatment) was randomly chosen one hour after a simulated overdose with sustained-release theophylline on four separate occasions in twelve healthy volunteers. 3. Syrup of ipecacuanha produced emesis in all twelve volunteers but only seven vomited any tablets. Gastric lavage yielded tablets in only one volunteer. 4. The mean systemic availabilities (areas under the concentration-time curves relative to control) of theophylline for ipecacuanha-induced emesis, gastric lavage and charcoal, were 107.1%, 101.1% and 16.9%, respectively. 5. Oral activated charcoal was thus highly effective, while gastric lavage and emesis were ineffective in preventing theophylline absorption. Activated charcoal is potentially the most effective first-line treatment for acute overdosage with sustained-release theophylline tablets.

Prevention of drug absorption in simulated theophylline overdose

To assess the effectiveness of oral activated charcoal and catharsis in preventing theophylline absorption, 12 healthy subjects, aged 20-35 years, received 3 x 200 mg sustained-release theophylline tablets and 16 radio-opaque placebo tablets on six occasions. On each occasion, they received either no treatment (control) or one of five treatments. Treatments were a) oral activated charcoal (Carbomix): 50 g at 1 h, 25 g at 5 h and 9 h; b) sorbitol 70%: 150 mL at 1 h; c) activated charcoal: 50 g at 6 h, 25 g at 10 h and 14 h; d) sorbitol 70%: 150 mL at 6 h; e) charcoal commencing at 6 h plus sorbitol at 6 h (i.e. a combination of treatments c and d). Plasma theophylline concentrations were measured and all stools collected over 36 h to assess placebo tablet recovery by radiography. Charcoal administration at 1 h was 91.2% effective in preventing theophylline absorption and at 6 h was 57.3% effective, while combined charcoal and catharsis at 6 h was 63.3% effective. Sorbitol-induced catharsis at 1 h and 6 h did not reduce theophylline absorption despite greater tablet recovery. Oral activated charcoal may be the most effective treatment for sustained-release theophylline overdose, with maximum benefit when administered soon after an overdose, though later administration might still be of value. Sorbitol catharsis is of no benefit either alone or in combination with charcoal.

Multiple-dose activated charcoal: a review of relevant clinical studies

Although many studies in animals and volunteers have demonstrated that multiple-dose activated charcoal increases drug elimination significantly, this therapy has not been shown in a controlled study in poisoned patients to reduce morbidity and mortality. Further clinical studies are required to establish its role and the optimum dosage regimen of charcoal to be administered. Based on current evidence, multiple-dose activated charcoal should only be considered if a patient has ingested a life-threatening amount of phenobarbital (phenobarbitone), carbamazepine, theophylline, quinine, dapsone or salicylate. In all of these cases there are data to confirm enhanced elimination, though no controlled studies have demonstrated clinical benefit.

Management of theophylline overdose patients in the intensive care unit

In a retrospective survey of all adults admitted to the Intensive Care Unit with acute theophylline poisoning over the last five years, we identified 38 patients (6.8% of all admissions for poisoning), two of whom died. Thirty-five (92%) had taken a sustained-release preparation. Eight patients had grand mal seizures and six developed arrhythmias (ventricular fibrillation, 3; atrial fibrillation, 2; supraventricular tachycardia, 1). Severe vomiting was present in 34 (89%) and proved to be a serious obstacle to the administration of enteral charcoal. The vomiting was controlled by intravenous metoclopramide in seventeen patients (50%), but the remaining seventeen required mechanical ventilation with sedation and muscle relaxation for the effective delivery of nasogastric charcoal. Importantly, in nine (24%), the serum theophylline concentration continued to rise despite enteral charcoal. Charcoal haemoperfusion was used in seven (18%). We present an algorithm for the management of severe, acute theophylline poisoning.

Role of repeated doses of oral activated charcoal in the treatment of acute intoxications

While single dose activated charcoal is effective in preventing drug absorption, repeated doses not only prevent absorption but also can increase systemic drug clearance. The mechanism for the latter effect may involve interruption of enterohepatic recycling and/or promotion of drug exsorption from the systemic circulation into the gut lumen. A comprehensive review of reported studies in volunteer subjects and overdose patients showed that repeated dose activated charcoal markedly decreased the half-life and/or increased the clearance of a wide range of drugs. Side-effects of the treatment were infrequent, but included aspiration pneumonia, diarrhoea and constipation. The addition of laxatives to repeated dose charcoal treatment did not offer any significant increase in drug clearance and is not recommended. It is suggested that the optimal regimen for the use of repeat dose activated charcoal in acute drug intoxications is an initial dose of 75-100 g, followed by 50 g every 4 hours until the risks of systemic drug toxicity are reduced to an acceptable level.

The effects of charcoal and sorbitol (alone and in combination) on plasma theophylline concentrations after a sustained-release formulation

1. The effects of charcoal and sorbitol, alone and in combination, were investigated in eight healthy female volunteers who received 600 mg slow-release theophylline (two 300 mg capsules). 2. The area under the plasma concentration time curve to 24 h (AUC0-24) after theophylline alone was significantly greater than after both the charcoal and charcoal plus sorbitol phase. 3. Charcoal and charcoal with sorbitol also significantly reduced the maximum plasma theophylline concentration (Tmax) and time to maximum concentration (Cmax). 4. Sorbitol significantly increased Cmax and shortened Tmax. 5. Although sorbitol did not reduce the adsorptive efficacy of charcoal, its use alone may be deleterious in poisoning with sustained-release theophylline products.

Kinetics of drug action in disease states. XXXIX. Effect of orally administered activated charcoal on the hypnotic activity of phenobarbital and the neurotoxicity of theophylline administered intravenously to rats with renal failure

The central nervous system (CNS) sensitivity to the hypnotic (general anesthetic) action of phenobarbital and to the neurotoxic (convulsive) action of theophylline is greater in rats with acute renal failure than in normal animals, consistent with clinical observations. In the case of phenobarbital, this increased sensitivity can be produced in normal rats by infusion of a solution of the lyophilized dialysate of serum from rats with renal failure. It was hypothesized that the relevant constituent(s) of this dialysate may circulate between the blood and the intestinal lumen and that it (they) can be adsorbed by orally administered activated charcoal and thereby removed from the body. If so, treatment of renal failure rats with activated charcoal should partly reverse the increased CNS sensitivity to phenobarbital and to other drugs similarly affected. Accordingly, rats with renal failure produced by bilateral ligation of ureters were given an aqueous suspension of activated charcoal, about 1 g per kg body weight, orally every 8 hr for six doses. Uremic controls received equal volumes of water. About 2 hr after the last dose, the animals were infused i.v. with phenobarbital to onset of loss of righting reflex or with theophylline to onset of maximal seizures. In the phenobarbital study, charcoal treatment partly reversed the hypothermia associated with renal failure and caused a reduction of creatinine and total bilirubin concentrations in serum. The cerebrospinal fluid (CSF) concentration of phenobarbital at onset of loss of the righting reflex was significantly higher in charcoal treated rats than in their controls.(ABSTRACT TRUNCATED AT 250 WORDS)

The assessment and treatment of theophylline poisoning

Theophylline poisoning long has been recognized as difficult to treat and still has an over-all mortality rate of about 10%. In recent years, the increasing use of sustained-release preparations has changed the pattern of toxicity. The management of theophylline toxicity is compounded by clinical differences between chronic (overmedication) intoxication and acute single ingestions of a large amount of the drug, inter- and intraindividual variability in theophylline metabolism and dose-dependent kinetics in poisoned patients. Management decisions should be based on both clinical assessment and laboratory information (particularly theophylline concentrations).

Hypermagnesemia. A potential complication during treatment of theophylline intoxication with oral activated charcoal and magnesium-containing cathartics

Toxic reaction to theophylline compounds is common. Oral activated charcoal (OAC) is a widely accepted mode of therapy for management of moderate to severe cases of theophylline toxicity. Magnesium-containing cathartics are generally recommended in conjunction with OAC in the treatment of drug or toxin ingestions. We report two cases of hypermagnesemia complicating the treatment of theophylline toxicity with OAC and magnesium citrate. In both patients, the hypermagnesemia contributed significantly to morbidity or mortality. In light of these cases and after review of the literature, we suggest that sorbitol be considered the cathartic agent of choice in the treatment of theophylline toxicity with OAC.

Evaluation of theophylline overdoses and toxicities

Patients presenting with elevated theophylline concentrations and manifestations of toxicity may be categorized as being either overdose or iatrogenic toxic. In addition to severe cardiac and neurologic toxicities, such as arrhythmias and seizures, OD patients probably require monitoring for manifestation of gastrointestinal hemorrhage, electrolyte abnormalities, and hypotension. The possibility of a delayed peak theophylline concentration after sustained release product ingestion must be considered. Patients with initial serum concentrations of less than 60 mg/L may receive a single dose of oral activated charcoal and have repeat concentrations drawn to ensure the avoidance of continued absorption. The presence of a serum concentration exceeding 60 mg/L in OD patients warrants initiation of elimination-enhancing modalities. Oral activated charcoal is the fastest and most readily available. Multiple-dose oral activated charcoal should be given until serum theophylline concentrations of 60 mg/L or less are reached. Cardiac monitoring and seizure precautions are recommended. Admission to the intensive care unit should be considered when serum concentrations do not decline after several hours of charcoal therapy or when seizures and severe cardiovascular manifestations occur. Patients having initial concentrations exceeding 100 mg/L and/or rapidly rising concentrations 100 mg/L over baseline values should be considered as candidates for CHP or RHP if available. If both CHP and RHP are unavailable or will be excessively delayed, HD is a reasonable alternative. Patients on chronic theophylline therapy (IA patients) presenting with symptoms of toxicity must be evaluated carefully. If serum concentrations are less than 20 mg/L, short-term observation or a reduction in dose should be sufficient. Patients with concentrations between 20 and 60 mg/L should be candidates for seizure precautions and cardiac monitoring. Oral activated charcoal may be started and continued until levels are below 20 mg/mL. Patients with concentrations in excess of 60 mg/L require intensive monitoring (including seizure precautions and cardiac monitoring) as well as initiation of MOAC or CHP/RHP as situation, availability, and patient tolerance dictate. Again, HD may be a reasonable alternative if the others are unavailable or contraindicated.

Dose-dependency in the exsorption of theophylline and the intestinal dialysis of theophylline by oral activated charcoal in rats

The elimination half-life of theophylline in serum after intravenous (i.v.) administration of aminophylline increased with increase in dose. Exsorption of theophylline from blood to the gastrointestinal tract was investigated after i.v. administration of aminophylline (10-50 mg kg-1) to rats by the in-situ single-pass perfusion technique. The exsorption rate of theophylline into the intestinal lumen also increased with increase in dose. When the dose of aminophylline was increased five-fold from 10 to 50 mg kg-1, the amount of theophylline exsorbed in 120 min was proportionally increased from 450 to 2300 micrograms. The average extent of theophylline exsorbed into the intestinal lumen was 12-15% after doses from 10-50 mg kg-1, while the extent of the drug excreted into the bile varied from 0.17-0.30% after doses from 10-50 mg kg-1. However, intestinal and biliary clearance of theophylline did not change significantly in the range 10 to 50 mg kg-1. Oral administration of multiple doses of activated charcoal reduced the serum theophylline levels after i.v. administration of aminophylline (50 mg kg-1) to rats. The serum half-life and the area under the serum concentration-time curve of theophylline were decreased to 52 and 50% by the charcoal treatment, respectively, while the total body clearance of the drug was increased to 188% compared with the corresponding control experiments. The volume of distribution was not significantly different between treated and control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Poor tolerance of oral activated charcoal with theophylline overdose

Vomiting is a common manifestation of theophylline toxicity and may limit the tolerance of orally administered activated charcoal (OAC). However, this potentially important interaction has received little attention. The records of 33 consecutive patients who presented to the emergency department with serum theophylline concentrations greater than 30 micrograms/ml and toxic symptoms and who were treated with OAC were reviewed. Seventeen (22%) of the 76 OAC doses were vomited. Six patients who had ingested theophylline as a single acute overdose vomited all 11 OAC doses administered, whereas 27 patients receiving chronic theophylline therapy vomited only six (11%) of 65 OAC doses. Vomited doses were associated with higher serum theophylline concentrations. Although theophylline-related vomiting preceded OAC intolerance in all acute toxicity patients, this condition was not predictive of OAC vomiting for chronic toxicity patients.

Intravenous theophylline poisoning and multiple-dose charcoal in an animal model

Large overdoses of IV theophylline (50 to 100 mg/kg) were administered to five canines on two separate occasions. On day one, with no charcoal administered, theophylline levels were serially obtained between ten minutes and 12 hours after infusion and the animals were recovered from anesthesia. Three days later the same dose of theophylline was administered, but then 50 g activated charcoal was placed through a nasogastric tube into the duodenum every hour for eight doses. In all five animals tested, activated charcoal significantly decreased the area under the serum concentration-time curve, decreased the half-life of elimination, and increased the clearance of theophylline. This effect on pharmacokinetics was not seen when the nasogastric tube was put into the stomach instead of the small bowel because the charcoal administered did not pass beyond the pylorus. In a separate experiment in which bile theophylline concentrations were measured, it was demonstrated that enhanced elimination was not from interruption of enterohepatic circulation of theophylline. This suggests that the demonstrated physiologic mechanism is that of gastrointestinal dialysis.

Role of extracorporeal drug removal in acute theophylline poisoning. A review

Theophylline, with its narrow therapeutic margin, is a common cause of iatrogenic and deliberate overdose. Most cases of self-poisoning are with sustained release preparations, with peak concentrations occurring up to 12 or more hours after overdose. Toxic symptoms are often seen at concentrations above 15 mg/L. Theophylline is metabolised within the cytochrome P-450 system, with an average total body clearance of 50 to 60 ml/min. Clearance is, however, affected by many factors such as other drugs or disease, and in overdose zero order kinetics may result in prolonged half-lives. Toxicity is characterised by agitation, tremor, nausea, vomiting, abdominal pains, seizures, and tachyarrhythmias. Hypokalaemia and metabolic acidosis are more profound in acute toxicity, and hypercalcaemia is usually present. Seizures occur at lower concentrations after chronic over-medication than after acute overdose. Gastric lavage should be performed in all patients presenting early, and an oral multiple dose charcoal regimen started with 50 to 100g charcoal, repeating with 50g doses and checking theophylline concentrations at 2- to 4-hour intervals. Multiple dose charcoal can be expected to double the clearance of theophylline, being as effective as a haemodialysis. Of the invasive techniques available, charcoal haemoperfusion is the most effective, increasing clearance 4- to 6-fold. Supportive care is particularly important. The aggressive supplementation of potassium, treatment of emesis with droperidol and ranitidine, and treatment of tachyarrhythmias and hypotension (possibly with propranolol), together with oral multiple dose charcoal may obviate the need for haemoperfusion. Seizures suggest increased morbidity and mortality. Charcoal haemoperfusion should be considered if plasma concentrations are greater than 100 mg/L in an acute intoxication or greater than 60 mg/L in a chronic intoxication. The decision to haemoperfuse should not be based on plasma concentrations alone, but an overall evaluation of the patient's laboratory and clinical status.

The new black magic: activated charcoal and new therapeutic uses

Activated charcoal has been used for centuries as antidotal therapy for poisonings. New variations of charcoal therapy have developed over the last two decades. These modifications include multiple-dose activated charcoal (MDAC) therapy, charcoal hemoperfusion, and a new "superactive" charcoal (SAC). Recent literature suggests using initial charcoal therapy instead of ipecac as a first-line antidotal agent for many acute poisonings. The palatability of charcoal slurries has been enhanced by the addition of carboxymethylcellulose, sucrose, saccharin, chocolate syrup, or sorbitol. The new SAC has shown to adsorb 1.7 to 4 times the amount of substance tested compared with other activated charcoal preparations. Multiple-dose activated charcoal therapy has been shown effective in treating phenobarbital, digoxin, digitoxin, theophylline, and dapsone intoxications, among others. The problems associated with charcoal hemoperfusion therapy have been partially alleviated, and it is now alternative therapy for the seriously intoxicated patient.

Absorption inhibition and enhancement of elimination of sustained-release theophylline tablets by oral activated charcoal

The effect of orally administered activated charcoal (OAC) on the first 12 hours of absorption and elimination of sustained-release theophylline tablets (SRT) was investigated in 20 normal children ages 8 to 18 years. The theophylline absorption-elimination characteristic of all subjects was determined after ingestion of 10 mg/kg SRT. Blood for theophylline was sampled at 0, two, four, six, eight, ten, 12, and 24 hours. After a 72-hour theophylline washout period, the subjects were assigned randomly to one of four study groups and received 10 mg/kg SRT. OAC then was given as a single dose one hour later to Group 1 subjects. Group 2 subjects took four doses of OAC at three-hour intervals beginning at one hour after SRT dosing. Group 3 subjects also received four doses of OAC at three-hour intervals with the first dose given three hours after SRT; Group 4 subjects received three doses at similar intervals with the first dose administered six hours after SRT dosing. OAC administration reduced the 12-hour area under the concentration time curve for theophylline (AUC) by 61% in Group 1, by 68% in Group 2, by 37% in Group 3, and by 18% in Group 4. The differences in AUC between treated and untreated subjects were significant at P less than .01 for Group 1, at P less than .001 for Group 2, at P less than .02 for Group 3, and not significant for Group 4. These data indicate that early OAC administration can inhibit SRT absorption significantly and enhance elimination of previously absorbed theophylline.

Theophylline poisoning. Pharmacological considerations and clinical management

The recent marketing of slow release preparations of theophylline and new indications for the use of the drug have resulted in a marked increase in the sale of theophylline products. This phenomenon combined with the drug's highly variable pharmacokinetics has led to an increase in the number of theophylline intoxications. The morbidity and mortality rates associated with theophylline intoxication are significant. Therefore it is essential that clinicians are aware of the pathophysiology, clinical presentation and treatment of this poisoning. Theophylline intoxication mainly affects the gastrointestinal, cardiovascular and central nervous systems. Signs and symptoms range from mild gastrointestinal upset to serious central nervous system manifestations such as seizures, a symptom often associated with a bad prognosis. Theophylline serum concentrations are very useful for making decisions regarding treatment. However, their interpretation should take into account several factors such as the age of the patient and the type of intoxication (acute versus chronic). Prevention of gastrointestinal absorption should be the principal objective of treatment of an oral theophylline poisoning. The repetitive administration of activated charcoal not only prevents theophylline absorption but also increases its rate of Once absorbed, external methods such as haemodialysis and haemoperfusion can significantly accelerate the elimination of the drug from the body. Finally, the rapid suppression of seizures and cardiac arrhythmias are essential to prevent severe neurological sequelae and death. Since theophylline intoxication can be potentially life-threatening, its administration should be monitored with regular measurements of the serum theophylline concentration, especially in the very young and the very old.

Gastrointestinal decontamination for acute poisoning

Gastric decontamination remains an important element in the therapy of pediatric poisoning; however, several issues remain unresolved. Additional studies, particularly in the clinical setting, are necessary to establish optimal therapeutic recommendations. Based on the data presented in this review, the following general recommendations can be made for gastric decontamination in children: If it is necessary to remove an ingested toxin, ipecac syrup is the preferred method if contraindications to its use are not present. The dose should be 30 ml in children older than 1 year of age and 10 ml in children 6 to 12 months of age. Pending further studies, the use of emetics in children younger than 6 months of age cannot be generally recommended, particularly in the home setting. Gastric lavage should be considered to be of very limited use in pediatric patients. Lavage using small nasogastric tubes, except under special circumstances, is nonproductive and cannot be advocated. If it must be used, a large-bore orogastric hose should be used. Administration of activated charcoal prior to lavage should be considered. In situations in which prompt induction of emesis is not possible or contraindications to emesis exist, activated charcoal followed by, or mixed with, a cathartic (preferably sorbitol) should be used as an alternative to removal of gastric contents. Patients with significant symptoms from ingestion requiring hospitalization should receive repeat doses of charcoal and cathartic until symptoms resolve. Activated charcoal should be given in conjunction with other appropriate therapies. Although the data to substantiate this recommendation are limited, particularly in pediatric patients, it is a benign therapy that holds promise of increasing drug elimination.

Treatment of theophylline toxicity with oral activated charcoal

We treated 14 patients who had an initial serum theophylline concentration greater than 30 micrograms/ml (48.3 +/- 19.4 micrograms/ml) and symptoms of theophylline toxicity with oral activated charcoal (OAC). Thirty-gram doses of OAC were administered approximately every two hours for two to four doses. Ten patients tolerated OAC and demonstrated a reduction in theophylline half-life to 5.6 +/- 2.5 hours with resolution of symptoms. Three of these ten patients were treated in the emergency department and discharged, making hospitalization unnecessary. The four patients with the highest initial theophylline concentrations (76.6 +/- 17.7 micrograms/ml) vomited all doses of OAC. Three of these four patients were treated with charcoal hemoperfusion with a reduction in the half-life to 5.2 +/- 1.0 hours. These data support the use of OAC as the primary therapeutic modality in the management of patients with theophylline toxicity. Patients with very high theophylline concentrations (greater than 50 micrograms/ml), however, usually vomit the OAC and may require charcoal hemoperfusion.