dofetilide is a class iii anti - arrhythmic agent proven to be safe and effective in the treatment of atrial fibrillation ( af ) , including in patients with congestive heart failure ( chf ) . a 71-year - old woman presented to our hospital with complaints of malaise , palpitations , and shortness of breath . she had a history of mitral regurgitation , af , and chronic obstructive pulmonary disease . her vital signs were : temperature 37c , heart rate 135 beats / min , blood pressure 152/68 mmhg , and oxygen saturation of 99% on 4 l of oxygen . on physical examination , the she appeared in mild respiratory distress and had crackles in both lung bases with diffuse wheezing . cardiac auscultation was significant for an irregularly irregular rate and a grade 2/6 holosystolic murmur . her initial laboratory tests were notable for the following : white blood cell ( wbc ) of 7400 cells / dl , hemoglobin of 13.4 mg / dl , creatinine 1.2 ng / ml and potassium of 3 mg / dl . her b - type natriuretic peptide was 1597 the electrocardiogram ( ecg ) revealed af with a ventricular rate of 134/min , and st segment depression in leads v5 and v6 , which was unchanged from prior ecg 's . initial management for the patient included controlling the heart rate with a continuous diltiazem drip at a dose of 10 mg / h and correcting her hypokalemia . the patient had recently failed electrical cardioversion and propafenone , 450 mg daily , therapy for her af . it was decided to attempt chemical cardioversion with dofetilide ( tikosyn ) capsules at a dose of 250 mcg twice daily . five hours after the first dose of dofetilide the patient started complaining of sharp , rapidly progressing right - sided facial pain , 10/10 in intensity on the functional pain scale . the temperature , blood pressure , and heart rate did not significantly change from before . at that time , she appeared to be in severe distress and avoided lying on her right side . she had severe tenderness over the entire right side of the face , unrelieved by a 4 mg of iv push of morphine . at this point , a work - up to exclude ischemic central nervous system pathology and maxillofacial disease , including temporomandibular joint ( tmj ) disease , was initiated . computed tomography scans of the brain and maxillofacial region did not reveal inflammation or other pathological processes . some of her laboratory data were an erythrocyte sedimentation rate of 14 mm / h , c - reactive protein 5.75 mg / l , wbc of 11,400 k / mm . she received a total of 3 doses , and after the second dose her rhythm converted to sinus on the ecg . however , the facial pain remained very difficult to control and was affecting her oral intake . at this point , it was decided to stop dofetilide therapy . in 12 h , the patient 's facial pain started to improve . however , she converted back to af with a rapid ventricular response , which required a dose of 360 mg of diltiazem cd daily for rate control . dofetilide ( available as tikosyn ) is a class iii anti - arrhythmic agent that works by prolonging the effective refractory period in the action potential of atrial and ventricular myocytes , and accessory pathways . it does so by selectively blocking the rapidly activating component ( ikr ) of the delayed rectifier cardiac potassium channel . available in the us in oral preparations only , it has demonstrated efficacy in converting af and flutter to sinus rhythm . with dosages of 125 , 250 or 500 mcg twice daily the conversion rate is 6% , 10% , and 30% , respectively . it works even better in maintaining the sinus rhythm . with a chronic dose of 500 mg bid , dofetilide has gained acceptance in the guidelines because of its proven safety in patients with chf with corrected qt interval of < 429 ms . however , dofetilide still carries a significant risk of provoking torsades de pointes ( 3% ) . more common , but less serious documented adverse effects of dofetilide include : headache 11% , chest pain 10% , dizziness 8% , respiratory tract infection 7% , and dyspnea 6% . a rare but notable side effect is facial paralysis ( < 2% ) . in our patient 's case , there was a clear temporal association between the administration and termination of dofetilide with the onset and resolution of intense facial pain resembling trigeminal neuralgia . a relatively extensive work up to rule out coincidental pathologies , such as nervous system masses or infections , tmj disease , and other inflammatory etiologies of this pain , was performed in consultation with neurology and included serological and imaging modalities . rechallenging the patient with dofetilide was not performed , and hence this side effect would fall under the probable / likely category of the who - umc causality assessment system . whether dofetilide caused this by interfering with neural cells ion channels is not known . although it is difficult to prove a direct causative relationship between the drug and this adverse effect , this case illustrates the importance of monitoring these symptoms and the early discontinuation of the drug because of the possibility of progression to trigeminal neuralgia or facial paralysis .
anti - arrhythmic medications are uncommonly used due to their pro - arrhythmic effect . 
 however , just like any other class of medication , they can cause idiosyncratic reactions that may or may not be related to their mechanism of action . 
 those reactions can be severe enough to warrant discontinuation of a successful therapeutic intervention . in this case , we present a case of trigeminal neuralgia caused by dofetilide .