L11: Digitalis & Theophylline Flashcards
Source of Digitalis
The roots, leaves and seeds of “Digitalis Purpurea” contain several poisonous glycosides.
Toxic Action of Digitalis
Risk factors for Digitalis Toxicity
- Age
- Renal functions
- Electrolyte indisturbances
- Drug Interactions
- Natural products
Age Risk Factors for Digotalis Toxicity
Adyanced age (>80 y) is associated with increased morbidity and mortality.
Renal Function Risk Factors for Digotalis Toxicity
Deteriorating renal function, dehydration, electrolyte disturbances or drug interactions, usually precipitates chronic toxicity.
Electrolyte Disturbances Risk Factors for Digotalis Toxicity
Drug Interactions Risk Factors for Digotalis Toxicity
- Drug interactions are one of the most common causes of digoxin Toxicity
(e.g., Beta-blockers, Calcium channel blockers, Quinidine, loop diuretics)
Natural Products Risk Factors for Digotalis Toxicity
Natural licorice should be avoided as it causes
- Sodium and water retention
- Increases potassium loss.
CP of Digitalis Toxicity
what causes yellow-green visual changes with digitalis toxicity?
due toxic effects on retinal con than rod cell.
Types of Digitalis Toxicity
- Acute overdose toxicity.
- Acute versus chronic use toxicity (more common).
Investigations in Digitalis Toxicity
TTT of Digitalis Toxicity
- Emergency TTT & Supportive
- Decontamination
- Antidote
- Enhanced Elimination
Emergency TTT of Digitalis Toxicity
- ABC and assist ventilation if necessary.
- Continuous cardiac monitoring for at least 12-24 hours after significant ingestion due to delayed tissue distribution
Continuous cardiac monitoring for at least 12-24 hours after significant ingestion of digitalis due to ……..
due to delayed tissue distribution
Aspects of Emergency TTT in Digitalis Toxicity
- Bradycardia or Heart block
- Ventricular Arrhythmias
- Hyperkalemia
- Hypokalemia
Emergenct TTT of bradycardia & Heart Block in Digitalis Toxicity
- Give atropine 0.5-2mg l.V.
- Temporary transvenous cardiac pacemaker may be needed
Emergency TTT of Ventricular Arrythmia in Digitalis Toxicity
- Fab is the preferred treatment for life-threatening arrhythmias.
- Lidocaine is the antiarrhythmic drug of choice.
Emergency TTT of hyperkalemia in Digitalis Toxicity
(VIP)
when does hyperkalemia of Digitalis Toxicity need TTT?
Needs treatment especially if associated with ECG changes
what to do in a case of Hyperkalemia due to digitalis if no FAB is available?
Give triad of
- Sodium bicarbonate (1 mEq/kg)
- Glucose (0.5 g/kg IV)
- Given simultaneously with Insulin (0.1 U/kg IV)
or Sodium Polystyrene Sulfonate (Kayexalate, 0.5 g/kg PO)
Types of TTT of Hyperkalemia associated with Digitalis Toxicity
Moderate elevation of serum k (>5.5 mEq/L):
- Fab Fragment: It rapidly reverses it
Progressive elevation of serum k (k > 6-7 mEq/ L):
- Bi-Carbonate/Glucose/Insulin
why shouldn’t calcium be used in hyperkalemia of Digitalis Toxicity?
may worsen ventricular arrhythmias.
Emergency TTT of hypokalemia of Digitalis Toxicity
why shouldn’t digoxin-specific Fab administration be used in hypokalemia of Digitalis Toxicity until hypokalemia is corrected?
Because reinstitution of Na+-K+-ATPase function may cause profound hypokalemia.
Deconatmination in Digitalis Toxicity
Antidote of Digitalis Toxicity
Fab Fragments
Indications of Fab fragments
MOA of Fab fragments
It is low molecular weight immunoglobulin fragments that bind to digitalis forming complex, which is cleared by the kidney and reticuloendothelial system.
Encanced Elimination in Digitalis Toxicity
is Digoxin hemodialyzable?
not dialyzable due to large volume of distribution
is Digitoxin Hemodialyzable?
dialyzable and can be eliminated by repeated-dose charcoal
- due to its enterohepatic circulation
Therapeutic index of theophylline
Theophylline has an extremely narrow therapeutic index
Intro to Theophylline toxicity
Toxic Action in Theophylline toxicity
Onset of Acute Theophylline toxicity
Manifestations of severe toxicity may be delayed 12-16 hours with sustained-release preparations
CP of Acute Theophylline toxicity
Causes of Chronic Theophylline toxicity
- when excessive doses are administered repeatedly over 24 hours or longer
- when intercurrent illness or an interacting drug interferes (Eg, erythromycin, cimetidine) with hepatic metabolism of theophylline.
Incidence of Chronic Theophylline toxicity
- The usual victims are very young infants and elderly patients, especially those with chronic obstructive lung disease.
Differences between Acute & Chronic Theophylline toxicity
In chronic toxicity:
- Vomiting and hypotension are less common than acute.
- Metabolic effects as hypokalemia and hyperglycemia are not present
- On the other houd, arrythmia and seizures are common at lower level.
Investigations in Theophylline toxicity
- Serum Theophylline Level
- Other Lab Studies
Seum Theophylline level
Other lab studies in Theophylline toxicity
Arterial blood gases (ABG), electrolytes, glucose, creatinine, hepatic function tests and ECG.
TTT aspects in Theophylline toxicity
- Emergency & supportive treatment
- Antidotes
- Decontamination
- Enhanced Elimination
Emergency & Supportive TTT in Theophylline toxicity
Is there an antidote for Theophylline toxicity?
no
Decontamination options in Theophylline toxicity
- Gastric Lavage
- Activated Charcoal
- Catharitic
- WBI
Gastic lavage in Theophylline toxicity
If no vomiting can be done even 4 hs after ingestion.
AC in Theophylline toxicity
- It is important to control nausea and vomiting first.
- “Ondansteron” is the drug of choice to control emesis in theophylline toxicity.
Catharitcs in Theophylline toxicity
Sorbitol is used with the activated charcoal.
WBI in Theophylline toxicity
With sustained-release preparations.
Enhanced Elimination options in Theophylline toxicity
- Hemodialysis
- MDAC
- Hemoperfusion
what is teh definitive Life-Saving Intervention in severe Theophylline toxicity?
Hemodialysis
Introducation to the use of hemodialysis in Theophylline toxicity
- It is the definitive life-saving intervention in severe theophylline poisoning
- Highly effective in achieving good clinical outcome if commenced early.
- Arrangements for urgent hemodialysis are made as soon as potentially life-threatening theophylline toxicity is anticipated.
Indications of the use of hemodialysis in Theophylline toxicity
what is the corner stone in TTT of Theophylline toxicity?
Multiple dose activated charcoal
uses of MDAC in Theophylline toxicity
- Used for stable patients with levels below 100 mg/L in acute toxicity.
- It enhances the elimination of theophylline
- but use of this modality delays effective treatment with hemodialysis in severe cases.
what is more effective in Theophylline toxicity, Hemodialysis or Hemoperfusion?
Hemoperfusion
Indications of Hemoperfusion in Theophylline toxicity?
Done in the presence of life-threatening toxicity.
- Persistent seizures
- persistent hypotension
- ventricular dysrhythmias
- If the serum level is greater than 100 mg/L in acute toxicity (If available).