Hypotension following the initiation of tizanidine in a patient treated with an angiotensin converting enzyme inhibitor for chronic hypertension

Baclofen and Tizanidine Adverse Effects Observed Among Community-Dwelling Adults Above the Age of 50 Years: A Systematic Review

OBJECTIVE

This review highlights adverse effects of baclofen and tizanidine in older community-dwelling adults.

DATA SOURCES

A literature search was conducted, including search terms of "adverse effect," "baclofen," "elderly," "falls," "fractures," and "tizanidine." Studies were included if they described community-dwelling adults aged 50 years and older who received oral baclofen or tizanidine. The Federal Drug Administration Adverse Event Reporting System (FAERS) data were compiled for adverse effect incidence.

STUDY SELECTION AND DATA EXTRACTION

The literature search was completed in July 2019 and updated in June 2023. Reviews performed by 2 independent reviewers yielded 15 records. FAERS identified 486 (baclofen) and 305 (tizanidine) adverse effects of interest.

DATA SYNTHESIS

Two retrospective cohort studies evaluating baclofen use in older adults showed increased hospitalizations for encephalopathy in chronic kidney disease (7.2% vs 0.1%) and end-stage renal disease (daily dose 20 mg or more; relative risk [RR] 19.8, 95% CI = [14.0-28.0]). Other articles were case reports; 10 articles reported dyskinesias, encephalopathy or disorientation, and drowsiness associated with baclofen, and 5 articles reported bradycardia and/or hypotension with tizanidine. The FAERS Public Dashboard revealed 12.1% and 28.7% overall incidence of adverse effects of interest, with a 27.8% and 29.2% incidence of falls for baclofen and tizanidine, respectively. Baclofen and tizanidine are associated with concerning adverse effects in older adults. Alternative agents should be considered, but, if necessary, providers should start at lower doses and increase slowly.

CONCLUSIONS

This review highlights the importance of using baclofen and tizanidine with caution in older adults.

Tizanidine Induced Hypotension: Report of a Case and Review of the Literature

INTRODUCTION

Spasticity is a common sequelae of stroke, and often these patients receive anti-spastic drugs such as baclofen or tizanidine. Stroke patients have multiple co-morbidities such as hypertension, diabetes, and seizure. Tizanidine is an α2 and imidazole receptor agonist at a spinal and supraspinal level resulting in reduced central sympathetic outflow and causing hypotension rarely, especially in those receiving beta-blockers or angiotensin-converting enzyme inhibitors.

CASE PRESENTATION

We report a 56-year-old hypertensive male presenting with altered sensorium who had recurrent intracerebral hemorrhage with left spastic hemiplegia and focal seizures. He was on amlodipine, atenolol, telmisartan and oxcarbazepine. After 3 doses of tizanidine 2mg, his blood pressure dropped from 140/90 to 80/40 mmHg and pulse from 82 bpm to 44 bpm. His blood counts, serum chemistry, procalcitonin, and Trop I were normal. ECG revealed sinus bradycardia. After 8 hours of withdrawing tizanidine, his blood pressure became 110/70 mmHg, and on the next day, it became 140/82 mmHg. His attendants were taught physiotherapy to minimize spasticity.

CONCLUSION

This patient highlights the need for close monitoring of patients receiving tizanidine co-medication with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. These drugs have a synergistic effect on reducing the renin-angiotensin-aldosterone system, thereby hypotension and bradycardia.

Co-Prescription of Strong CYP1A2 Inhibitors and the Risk of Tizanidine-Associated Hypotension: A Retrospective Cohort Study

Tizanidine, a widely used muscle relaxant that can lower blood pressure, is metabolized by the cytochrome P450 1A2 (CYP1A2). We studied 1,626 patients prescribed tizanidine and 5,012 prescribed cyclobenzaprine concurrently with a strong CYP1A2 inhibitor. The primary outcome was severe hypotension, defined as systolic blood pressure (SBP) ≤ 70 mmHg during periods of drug co-exposure. Severe hypotension occurred more often in the tizanidine group (2.03%; n = 33) than the cyclobenzaprine group (1.28%; n = 64); odds ratio (OR) = 1.60; P = 0.029. This difference remained statistically significant after adjustment for a log-transformed propensity score that included age, sex, race, Charlson's comorbidity index, and concurrent use of antihypertensive medications (OR = 1.57; P = 0.049). A sensitivity analysis that defined hypotension as SBP < 90 mmHg also yielded higher rates of hypotension among patients prescribed tizanidine. In conclusion, CYP1A2 inhibition increases the risk of hypotensive episodes associated with the use of tizanidine in routine clinical practice.

Tizanidine-induced acute severe cystitis in a female taking famotidine

Cystitis is a possible adverse drug reaction associated with the use of tizanidine. Such cases have been rarely reported in literature because of the difficulty in establishing the causality. However, from a pharmacovigilance point of view, it is better to report such cases of a possible association between a drug’s use and potential adverse drug reactions. We report a case of a 26-year-old Asian female on famotidine who presented with acute severe urinary burning after taking tizanidine.

Profound symptomatic bradycardia requiring transvenous pacing after a single dose of tizanidine

BACKGROUND

We report a case of profound symptomatic bradycardia after a single dose of tizanidine.

CASE REPORT

A 93-year-old female became altered and was found to have hypotension and profound symptomatic bradycardia 30 min post ingestion of a single 4-mg dose of tizanidine at her physician's office. Emergency Medical Services was called to scene and patient was transported to our tertiary medical center. In the emergency department, the patient required intubation, vasopressor support, and transcutaneous pacing. An electrocardiogram revealed atrial fibrillation with slow ventricular response with a heart rate of 19 beats/min. The patient was transferred to the intensive care unit and subsequently taken for cardiac catheterization, where a transvenous pacer was placed. During the next few days, her vital signs and mental status improved, allowing for successful extubation. Before discharge, the patient received a single-chamber pacemaker.

DISCUSSION

Profound symptomatic bradycardia from a single dose of tizanidine has not been reported. A review of the patient's medications did not reveal a significant cytochrome P450 drug interaction to result in an adverse effect as previously reported in the literature.

CONCLUSIONS

Tizanidine should be used cautiously in elderly population and drug interactions screening should be performed.

Limitations and obstacles of the spontaneous adverse drugs reactions reporting: Two "challenging" case reports

Introduction:

Nowadays, based on several epidemiological data, iatrogenic disease is an emerging public health problem, especially in industrialized countries. Adverse drugs reactions (ADRs) are extremely common and, therefore, clinically, socially, and economically worthy of attention. Spontaneous reporting system for suspected ADRs represents the cornerstone of the pharmacovigilance, because it allows rapid detection of potential alarm signals related to drugs use. However, spontaneous reporting system shows several limitations, which are mainly related to under-reporting. In this paper, we describe two particular case reports, which emphasize some reasons of under-reporting and other common criticisms of spontaneous reporting systems.

Materials and Methods:

We performed a computer-aided search of Medline, PubMed, Embase, Cochrane library databases, national and international databases of suspected ADRs reports in order to identify previous published case reports and spontaneous reports about the ADRs reviewed in this paper, and to examine the role of suspected drugs in the pathogenesis of the described adverse reactions.

Results:

First, we reported a case of tizanidine-induced hemorrhagic cystitis. In the second case report, we presented an episode of asthma exacerbation after taking bimatoprost. Through the review of these two cases, we highlighted some common criticisms of spontaneous reporting systems: under-reporting and false causality attribution.

Discussion and Conclusion:

Healthcare workers sometimes do not report ADRs because it is challenging to establish with certainty the causal relationship between drug and adverse reaction; however, according to a key principle of pharmacovigilance, it is always better to report even a suspicion to generate an alarm in the interest of protecting public health.

Hypotension and bradycardia associated with concomitant tizanidine and lisinopril therapy

PURPOSE

A case of severe bradycardia and hypotension associated with concomitant tizanidine and lisinopril therapy is reported.

SUMMARY

An 85-year-old man with a chief complaint of profound weakness was admitted to the hospital with a blood pressure reading of 60/32 mm Hg and a heart rate of 37 beats/min. His medical history included type 2 diabetes mellitus, congestive heart failure, gastroesophageal reflux disease, chronic obstructive pulmonary disease, osteoarthritis, restless leg syndrome, benign prostatic hyperplasia, generalized anxiety disorder with depression, and severe chronic back pain for which he was receiving treatment at a pain clinic. Two days before hospital admission, he had been seen at the pain clinic and started on ti-zanidine. Additional medications included acetaminophen, chlorpromazine, citalopram, finasteride, lidocaine patch, lisinopril, metformin, pramipexole, omeprazole, simvastatin, theophylline, diclofenac topical gel, hydrocodone-acetaminophen, and ondansetron. After taking three doses of the newly prescribed tizanidine, he developed severe hypotension and bradycardia. Notable laboratory test values included a serum creatinine concentration of 1.90 mg/dL, a blood urea nitrogen concentration of 21 mg/dL, a serum potassium concentration of 5.5 meq/L, and a serum sodium concentration of 128 meq/L. Upon admission, tizanidine, lisinopril, theophylline, omeprazole, and simvastatin were withheld, and i.v. fluids were administered. The patient's vital signs began to gradually improve. Within 24 hours, the patient's blood pressure and heart rate had improved, as had the previously abnormal laboratory test values. Tizanidine was discontinued, and all of his other preadmission medications were restarted at discharge.

CONCLUSION

The addition of tizanidine in a patient receiving long-term treatment with lisinopril was associated with severe hypotension and bradycardia.

Pediatric safety of tizanidine: clinical adverse event database and retrospective chart assessment

BACKGROUND

Tizanidine is an imidazoline with central alpha(2)-adrenoceptor agonist activity at both spinal and supraspinal levels, which is indicated as a short-acting drug for the management of spasticity. Despite being used in pediatric populations, there is no adequate information or well controlled studies to document the safety and efficacy of tizanidine in this group.

OBJECTIVE

To evaluate the safety of tizanidine in the pediatric population. We compared spontaneous adverse event reports in the Acorda Therapeutics worldwide clinical adverse event database for children (< or = 16 years; n = 99) and adults (>16 years; n = 1153) who had received tizanidine and for whom at least one adverse event was reported, and performed a retrospective chart review of the safety of tizanidine in children (< or = 16 years; n = 76) at a large US pediatric neurology practice. Causality of adverse events in our worldwide clinical adverse event database were neither assessed nor assigned by the company.

RESULTS

When adverse events from the clinical adverse event database were collapsed into the 25 Medical Dictionary for Regulatory Activities (MedDRA; version 9.0) organ system classes, five classes were more frequent in adults (general disorders and administration site conditions [p = 0.0006], hepatobiliary disorders [p = 0.0031], nervous system disorders [p = 0.0108], skin and subcutaneous disorders [p = 0.0063], and vascular disorders [p = 0.0029]), while one class was more frequent in children (psychiatric disorders [p < 0.0001]). The most common adverse event classes in children were psychiatric disorders (52.5%) followed by nervous system disorders (29.3%), and gastrointestinal disorders (16.2%), whereas the most common adverse event classes in adults were nervous system disorders (42.4%), general disorders and administration site conditions (28.6%), and gastrointestinal disorders (21.3%). Serious adverse events were substantially less frequent in children than adults (19.2% vs 45.9%) in the clinical adverse event database. In the pediatric practice chart review, the incidence of adverse events in the MedDRA psychiatric disorders class was very similar (52.6%) to that for children in the clinical adverse event database, while the next most common classes were gastrointestinal disorders (14.5%), and nervous system disorders (13.2%). There were three deaths in children across the databases, including one from accidental exposure and two from cardiac events; the relationship of cardiac events in relation to tizanidine or other causes was difficult to assess with the limited available information.The major causes of death in adults were related to suicide or overdose. Minor, transient liver transaminase increases were occasionally reported; the effect of tizanidine could not be ruled out.

CONCLUSION

The overall safety of tizanidine in the pediatric group appeared good; however, the adverse event profile differed from that in adults. This difference most likely reflects the off-label use of tizanidine as adjunctive treatment for attention disorders and autism. The frequency and nature of adverse events in adults were consistent with the tizanidine prescribing information as reported for its approved indication, i.e. management of spasticity.

Hypotension Due to Interaction Between Lisinopril and Tizanidine

OBJECTIVE

To report a case in which significant hypotension occurred after initiation of tizanidine in a patient using the antihypertensive agent lisinopril.

CASE SUMMARY

A 48-year-old woman was admitted due to cerebral hemorrhage at the midbrain and pons, with extension to the fourth ventricle. Consciousness disturbance (Glasgow coma scale 4) with a decerebrate posture improved 5 days after stroke onset. As the BP was fairly high, antihypertensive agents, including lisinopril, were initiated. Three weeks later, the decerebrate rigidity and high BP remained, and tizanidine was initiated to see whether the decrease in muscle tone could facilitate hypertension control and motor recovery. However, the BP dropped dramatically within 2 hours after the first dose of tizanidine. The tizanidine and all of the antihypertensive medications were withdrawn. Tizanidine was used again after her BP had stabilized, but did not produce similar problems.

DISCUSSION

A similar event was reported in 2000. The reaction in our patient appeared after tizanidine initiation and improved after both lisinopril and tizanidine were discontinued. According to the Naranjo probability scale, this was classified as a possible drug interaction. This kind of reaction is seldom mentioned as occurring during co-administration with tizanidine. With its characteristics, tizanidine has the potential to compromise hemodynamic stability during concomitant angiotensin-converting enzyme inhibitor use.

CONCLUSIONS

Based upon the literature review, the hypotension in this patient was possibly due to the interaction between tizanidine and lisinopril.