Please assess the completion status of the following clinical trial:

Trial Title: Effectiveness of Mexiletine for Treating People With Non-Dystrophic Myotonia

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: CROSSOVER
- Observational Model: None
- Primary Purpose: TREATMENT
- Time Perspective: None
- Masking: DOUBLE
- Phase: PHASE2
- Number of Arms: 2.0

Eligibility Criteria:
Inclusion Criteria:~* Clinical symptoms or signs suggestive of myotonic disorders~* Presence of myotonic potentials on electromyography (EMG)~* Participant in the Non-Dystrophic Natural History study (RDCRN 5303) or a new patient with confirmed non-dystrophic myotonia~Exclusion Criteria:~* Other neurological condition that might affect the assessment of the study measurements~* Genetic confirmation of DM1 (more than 50 repeats of CTG) or DM2~* Existing cardiac conduction defects, as evidenced on EKG, including but not limited to the following conditions: malignant arrhythmia or cardiac conduction disturbances (e.g., second degree AV block, third degree AV block, or prolonged QT interval)~* Existing permanent pacemaker~* Current use of any of the following antiarrhythmic medications for a cardiac disorder: flecainide acetate, encainide, disopyramide, procainamide, quinidine, propafenone, or mexiletine~* Use of medications for myotonia, such as phenytoin and flecainide acetate, within 5 days of study entry; carbamazepine and mexiletine within 3 days of study entry; or propafenone, procainamide, disopyramide, quinidine, and encainide within 2 days of study entry~* Use of medications that produce myotonia, which may include fibrate acid derivatives, hydroxymethylglutaryl CoA reductase inhibitors, chloroquine, and colchicines~* Kidney or liver disease~* Heart failure~* Seizure disorder~* Pregnant or breastfeeding

- Gender: ALL
- Minimum Age: 16 Years
- Maximum Age: None
- Healthy Volunteers: f

Study Arms:
- 1 (Type: EXPERIMENTAL): Participants will receive mexiletine for 4 weeks, then no intervention for 1 week, and finally placebo for 4 weeks.
- 2 (Type: EXPERIMENTAL): Participants will receive placebo for 4 weeks, then no intervention for 1 week, and finally mexiletine for 4 weeks.

Based on this trial design, predict the completion outcome and termination type (if applicable).