Class IB Flashcards
What are the three drugs in class IB?
- Lidocaine
- Mexiletine
- Tocainide
What is the mechanism of drugs in class IB?
- Dec. AP duration
- Preferentially affects ischemic/depolarized purkinje and ventricular tissue
What are the cardiac effects of Lidocaine, Mexiletine and Tocainide?
- Selective depression of conduction in depolarized cells
- Little effect seen on EKG in normal sinus rhythm
What are the extra cardiac effects of Lidocaine?
-Block generation & conduction of nerve impulses, increasing the threshold of excitation–> slows propagation = no pain
What are the extra cardiac effects of Mexiletine?
-Significantly effective at relieving chronic pain, especially due to diabetic neuropathy and nerve injury
What are the extra cardiac effects of Tocainide?
None
What are the pharmacokinetics of Lidocaine?
- Extensive 1st pass metabolism (3% orally available) –> given parenterally
- Half life: 1-2 hours
What are the pharmacokinetics of Mexiletine?
- 90% oral absorption
- Peak plasma concentration at 2-3 hours
- Low first pass metabolism
What are the pharmacokinetics of Tocainide?
No significant 1st pass metabolism
What is the toxicity of Lidocaine?
- Minimal
- Parasthesias, tremor, nausea, light headedness, hearing disturbances, slurred speech and convulsions (mostly elderly or vulnerable patients)
What is the toxicity of Mexiletine?
- Possible development/exacerbation of arrhythmias (monitor before an during use)
- Possible exacerbation of Hypotension and CHF
- Possible decreased liver function
- Possible leukopenia, agranulocytosis and thrombocytopenia
What is the toxicity of Tocainide?
Similar to lidocaine:
- Minimal
- Parasthesias, tremor, nausea, light headedness, hearing disturbances, slurred speech and convulsions (mostly elderly or vulnerable patients)
What is the therapeutic use of Lidocaine?
- Terminating V-Tach and Preventing V-Fib AFTER cardioversion in acute ischemia
- Prophylactic use may actually INCREASE mortality
What is the therapeutic use of Mexiletine?
- Tx of documented life-threatening ventricular arrhythmias (sustained VTACH)
- Not for less severe arrhythmias
What is the therapeutic use of Tocainide?
No longer available in USA
