What are Class B/B* (B/B star) drugs?

Class B/B* Drugs in Psychotropic Medication Risk Classification

Class B and B drugs are psychotropic medications with documented QT-prolonging potential that require cardiac risk assessment before initiation and ECG monitoring during treatment, unlike Class A drugs which can be started without cardiac evaluation.* 1

Definition and Clinical Significance

Class B and B* drugs represent a cardiac risk stratification category specifically developed for psychotropic medications that have demonstrated pro-arrhythmic potential. 1 These medications require structured cardiac assessment before prescribing, distinguishing them from safer Class A alternatives. 1

Key Characteristics

• QT prolongation risk: These drugs prolong ventricular repolarization, increasing the risk of torsades de pointes (TdP) ventricular tachycardia and sudden cardiac death (SCD). 1
• Mandatory pre-treatment evaluation: Unlike Class A drugs, Class B/B* agents cannot be initiated without cardiac risk assessment. 1
• Monitoring requirements: ECG surveillance is required at baseline and within 1-2 weeks after initiation (at steady-state, approximately 5 drug half-lives). 1

Pre-Treatment Assessment Requirements

Before initiating any Class B or B* psychotropic medication, the following structured evaluation is mandatory: 1

Medical History Components

• Cardiac disease history: Previous myocardial infarction, heart failure, or structural heart disease 1
• Symptom assessment: Chest pain, dyspnea, palpitations, near-syncope, or syncope 1
• Family history: Sudden cardiac death in relatives 1
• Medication review: Identify other QT-prolonging drugs, potassium-wasting diuretics, and potential drug interactions 1

Baseline Testing

• 12-lead ECG: Assess for conduction disorders, signs of heart disease, and baseline QTc interval 1
• Electrolyte panel: Check potassium, magnesium, and calcium levels 1

Monitoring Protocol During Treatment

Follow-Up ECG Timing

Repeat ECG within 1-2 weeks after drug initiation or any significant dose increase. 1 This timing corresponds to steady-state drug levels (approximately 5 half-lives). 1

Critical QTc Thresholds

• QTc >500 ms: Indicates definitely increased risk of TdP and should prompt drug discontinuation in most cases 1
• QTc increase >60 ms from baseline: Also warrants discontinuation in most situations 1

When to Refer to Cardiology

Consider cardiology consultation if any of the following are present: 1

• Structural heart disease identified
• Baseline QT prolongation
• Persistent electrolyte disturbances
• Cardiac symptoms during treatment

Risk Factor Optimization

Modifiable Cardiac Risk Factors

Before continuing Class B/B* drugs when risks are identified: 1

• Electrolyte correction: Normalize potassium, magnesium, and calcium levels 1
• Drug interaction management: Discontinue or replace other QT-prolonging medications when possible 1
• Consider alternative agents: Switch to Class A drugs with more favorable cardiac profiles if clinically appropriate 1

High-Risk Populations Requiring Extra Caution

• Elderly patients: Risk of ischemic heart disease increases dramatically with age, with SCD rates reaching 800 per 100,000 in 75-year-old men 1
• Structural heart disease: Patients with heart failure or ischemic heart disease have the highest SCD rates when exposed to pro-arrhythmic drugs 1
• Multiple QT-prolonging medications: Additive effects significantly increase risk 2

Clinical Decision Algorithm

Step 1: Determine if psychiatric condition requires pharmacotherapy 1

Step 2: Select appropriate psychotropic medication at recommended dose 1

Step 3: Classify drug as Class A, B, or B* 1

Step 4: If Class B/B* selected:

• Perform complete cardiac risk assessment (history, medication review, ECG) 1
• If cardiac risks identified: optimize risk factors AND/OR choose Class A alternative 1
• If structural heart disease, QT prolongation, electrolyte issues, or symptoms present: consider cardiology referral 1

Step 5: Initiate treatment with close monitoring 1

Step 6: Repeat ECG at 1-2 weeks and after any significant dose increase 1

Step 7: Discontinue if QTc >500 ms or increase >60 ms from baseline 1

Exception for Severe Psychiatric Illness

When psychiatric conditions are invalidating or life-threatening, higher cardiac risk may be accepted, but this requires reduction of all reversible risk factors and close follow-up. 1 This represents the only scenario where continuing Class B/B* drugs despite identified cardiac risks is appropriate. 1

Common Pitfalls to Avoid

• Failing to obtain baseline ECG: This prevents comparison when follow-up ECGs show QT changes 1
• Ignoring drug-drug interactions: Multiple QT-prolonging agents have additive effects 2
• Inadequate electrolyte monitoring: Hypokalemia and hypomagnesemia significantly increase TdP risk 1
• Missing follow-up ECGs: The 1-2 week timing is critical as steady-state levels are reached 1
• Continuing therapy despite QTc >500 ms: This threshold represents definite increased risk requiring action 1