====== Tachyarrhythmias ======

The most common drugs ingested which prolong QRS & QT intervals and cause tachyarrhythmias are:

  * [[:wikitox:2.1.11.9.2.1_tricyclic_antidepressants|Tricyclic antidepressants]] *
  * [[:wikitox:2.1.11.9.3_antipsychotics|Antipsychotic drugs]] (particularly thioridazine) *
  * [[:wikitox:2.1.11.4.2_antihistamines|Antihistamines]] (particularly terfenadine and astemizole)
  * [[:wikitox:2.1.11.2_anticonvulsants|Anticonvulsants]] (particularly carbamazepine and phenytoin) *
  * [[:wikitox:antimalarial_drugs|Antimalarial drugs]] (chloroquine, quinine) *
  * [[:wikitox:3.4.3.4.2_beta_blockers|Beta blockers]] (only propranolol and sotalol) *
  * [[:wikitox:2.1.6.1.2_cardiac_glycosides|Digoxin]] *
  * [[:wikitox:3.4.3.4_antiarrhythmics|Antiarrhythmic drugs]] *
  * [[:wikitox:2.1.11.4.1_anticholinergics|Orphenadrine]] *
  * [[:wikitox:2.1.11.9.4_mood_stabilizers|Lithium]] *
  * [[:wikitox:2.1.11.9.1_miscellaneous_anxiolytics_and_sedative_hypnotics|Chloral hydrate]]

*These drugs may also cause bradyarrhythmias

These drugs are often referred to as having [[:wikitox:quinidine_like_effects|'quinidine-like' effects, 'membrane-stabilising' properties or 'nonspecific toxicity']].

For more mechanistic detail and clinical evaluation see [[:wikitox:cardiotoxic_drugs|Cardiotoxic Drugs]]


===== IN ADDITION =====

Adrenergic drugs ([[:wikitox:2.1.11.4.8.2_theophylline|theophylline]], salbutamol, [[:wikitox:2.1.11.4.8.1_cocaine|cocaine]] and amphetamines) cause tachyarrhythmias without causing preceding QRS & QT prolongation.

A number of drugs that lead to tissue hypoxia, acidosis or hypoglycaemia ([[:wikitox:2.2.9.1.1_carbon_monoxide|CO]], [[:wikitox:2.2.7.4.4_organochlorines|organochlorines]], [[:wikitox:2.1.7.1.2_sulphonylureas|hypoglycaemic drugs]], isoniazid, [[:wikitox:2.1.1.4_salicylates|salicylates]] etc.) may cause ventricular arrhythmias without marked preceding ECG changes.

Features that help to differentiate between these drugs are:

[[:wikitox:type_of_arrhythmia|TYPE OF ARRHYTHMIA]]\\
[[:wikitox:level_of_consciousness_prior_to_arrhythmia|LEVEL OF CONSCIOUSNESS PRIOR TO ARRHYTHMIA]]\\
[[:wikitox:3.1.3_seizures|SEIZURES]]\\
[[:wikitox:heart_rates|HEART RATE PRIOR TO ARRHYTHMIA]]\\
[[:concept_ecg_changes|ECG CHANGES PRIOR TO ARRHYTHMIA]]\\
[[:wikitox:pupil_size_and_reaction|PUPIL SIZE & REACTION]]\\
[[:wikitox:response_to_antagonists|RESPONSE TO ANTAGONISTS]]\\
[[:wikitox:electrolytes_and_blood_glucose|ELECTROLYTES/BLOOD GLUCOSE]]\\
[[:wikitox:blood_concentrations|BLOOD CONCENTRATIONS]]\\
\\
It is important to try to make the correct diagnosis, as there are [[:wikitox:3.4.3.1_cardiac_arrhythmias_and_cardiac_arrest|specific treatments]].