Diphenhydramine-Induced Antimuscarinic Delirium Treated with Physostigmine and Transdermal Rivastigmine.

INTRODUCTION: Recurrent physostigmine shortages present a challenge to healthcare providers treating antimuscarinic delirium. Other centrally acting acetylcholinesterase inhibitors such as rivastigmine may represent a therapeutic alternative or adjunct during physostigmine shortage; however, previous reports of use have not documented serum antimuscarinic toxin concentrations, limiting evaluation of effectiveness. Combination therapy with physostigmine and rivastigmine has not been described. In this report, the authors present a case of diphenhydramine-induced antimuscarinic delirium with elevated diphenhydramine serum concentrations treated with physostigmine and transdermal rivastigmine without observed adverse effect. CASE REPORT: A 48-year-old female presented to an emergency department after ingesting 3.75 g (41.2 mg/kg) of diphenhydramine. She had antimuscarinic delirium with a presenting serum diphenhydramine concentration of 1500 ng/mL (therapeutic range, 25-112 ng/mL) and required two doses of physostigmine to avert intubation prior to intensive care unit (ICU) admission. At hospital hour 22, in the ICU, antimuscarinic delirium persisted but no further physostigmine was available due to hospital shortage. Therefore, a 9.5-mg transdermal rivastigmine patch was applied. By hospital hour 24, her delirium had resolved. A serum diphenhydramine concentration at hospital hour 25 was elevated at 760 ng/mL. Transdermal rivastigmine was discontinued at hospital hour 48 without recurrent delirium. Despite persistent normal mental status after rivastigmine discontinuation, the patient had a dry mouth, difficulty urinating, and mydriasis until hospital day 5. She never developed muscarinic toxicity. DISCUSSION: Transdermal rivastigmine may be a useful treatment alternative or adjunct during physostigmine shortage for antimuscarinic delirium and has a long duration of action without aspiration risk. Muscarinic toxicity was not observed.

The cholinesterase inhibitor physostigmine for the local treatment of dry mouth: a randomized study.

Application of physostigmine to the oromucosal surface with the aim of stimulating underlying mucin-producing glands while reducing cholinergic systemic effects might be a strategy for treating dry mouth. Subjects suffering from dry mouth and with hyposalivation participated in a crossover, double-blind, randomized study. A gel containing physostigmine (0.9, 1.8, 3.6, and 7.2 mg) or placebo was applied to the inside of the lips and distributed with the tongue. The feeling of dryness was assessed using a visual analogue scale (VAS) (where a score of 100 = extremely dry) and systemic effects were registered. Based on assessments of efficacy and safety, the dose of 1.8 mg of physostigmine was selected for use in the second part of the study to make objective measurements of saliva volumes. Physostigmine (1.8 mg) produced long-lasting (120 min) relief (evident as a score reduction of 25 on the VAS) in the feeling of dryness. Judging from AUC values related to baseline over 180 min, the improvement for both mouth and lips in response to physostigmine was six times greater than that to placebo. At higher doses of physostigmine, gastrointestinal discomfort predominantly occurred. The volume of saliva collected in response to physostigmine was five times higher over 180 min than that collected in response to placebo. Physostigmine, applied locally, therefore appears to be a promising modality for dry-mouth treatment.

Physostigmine salicylate as an antidote.

Most poisonings with anticholinergics deal with simple cases without diagnostic or therapeutic difficulties; however, in difficult or unclarified cases a new method for diagnosis and treatment is the antidote physostigmine salicylate. Within 15 minutes after application of 2 mg of the antidote the central anticholinergic symptoms disappear, such as respiratory depression, coma, cramps and hallucinations as do the peripheral anticholinergic symptoms as cardiac rhythm disturbance, dry mouth and red dry skin. No fatal overdose with anticholinergic drugs occurs if the antidote is given in time.

[Etiology of initially unexplained confusion of excitability in deadly nightshade poisoning with suicidal intent. Symptoms, differential diagnosis, toxicology and physostigmine therapy of anticholinergic syndrome]. / Atiologisch zunächst unklare Verwirrtheit und Exzitation im Verlauf einer Tollkirschenvergiftung mit suizidaler Absicht. Symptomatik, Differentialdiagnose, Toxikologie und Physostigmin-Therapie des anticholinergen Syndroms.

HISTORY AND ADMISSION FINDINGS: After a walk in a wood a 55-year-old teacher was admitted to the emergency unit of a university hospital because of somnolence and excitability. Her rectal temperature was 37.8 degrees C, she had sinus tachycardia (rate of 130/min) but no other significant findings. INVESTIGATIONS: With the exception of C-reactive protein (10 mg/dl), MCV (101 fl), MCH (34 pg) and arterial blood gases (pH 7.483, pCO2 35.5 mmHg, base excess 5.1 mmp/l) laboratory tests were within normal limits. Qualitative screening of serum for benzodiazepines, barbiturates and antidepressives was negative. Neurological examination, including lumbar puncture and cranial computed tomography were noncontributory. TREATMENT AND COURSE: 10 hours after admission the patient developed signs of an anticholinergic syndrome with mydriasis, dry mouth, tachycardia, hot skin and an atonic bladder. Physostigmine 2 mg completely reversed the neurological and mental symptoms. After gas chromatography, mass-spectrometry of a urine sample showed an atropine molecular fragment with a molecular weight of 271. At intervals of 3 to 5 hours the recurrence of confusion and excitability required 4 further i.v. injection of physostigmine. The patient subsequently became accessible to psychiatric examination and reported that during the walk she had swallowed 8-10 berries of deadly nightshade with suicidal intent. CONCLUSION: In case of excitability and confusion as well as somnolence or coma of uncertain aetiology an anticholinergic syndrome caused by ingestion of atropine-containing plants or psychoactive drugs (phenothiazines, butyrophenones, tri- or tetracyclic antidepressants) should be included in the differential diagnosis. If there are suggestive clinical findings (tachycardia, somnolence, coma or threatened respiratory arrest, physostigmine should be given if there are no contraindications.