An bolus delivery system includes an implantable pump, a sensor for sensing an adverse patient condition, such as atrial fibrillation, and a catheter for delivery of a bolus of drug to a target area of a living body. The coupling assembly includes a longitudinally split coupler having a pair of coupling halves rotatable about a hinge. The system also includes an air filter box having an air filter that is in fluid communication with an air pocket in the reservoir. Exemplary process flows include alternately pulsed metal halide and ammonia gases injected into a constant carrier flow. Using this technique the current consumption of the prescaler frequency dividers need not be increased in an effort to reduce the prescaler noise, thereby conserving current in battery powered and other applications. Methods of drawing fluid from the vessels using the pressure source, and moving the magnets to form a pellet of analyte are also included.