Hypotension Due to Interaction Between Lisinopril and Tizanidine

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.

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.

Population-Based Assessments of Clinical Drug-Drug Interactions: Qualitative Indices or Quantitative Measures?

Population-based assessments of drug-drug interactions have become more common since the introduction and acceptance of the population pharmacokinetic approach. Unlike traditional methods, population-based studies provide clinically relevant results that can be applied directly to a target patient population. Furthermore, population-based studies do not demand the traditional requirements of intensive pharmacokinetic sampling, rigorous inpatient stays, or stringent assessment schedules. As such, the population-based approach can effectively be used to confirm known drug-drug interactions and further characterize anticipated interactions. A prospectively designed analysis can also reveal drug-drug interactions that might otherwise have gone undetected with traditional methods. Ultimately, these results could help to alleviate clinicians' concerns about using widely marketed drugs in combination therapies and also reduce patients' risk of experiencing unacceptable side effects. This article intends to provide a balanced overview of the population-based approach and its merits, drawbacks, and potential utility in the assessment of drug-drug interactions during clinical drug development.

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.

Potential side effects of renin inhibitors – mechanisms based on comparison with other renin–angiotensin blockers

Angiotensin (Ang) II plays important roles in the development of hypertension and cardiovascular and renal injury. Pharmaceutical approaches to block its activity led to the development of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Numerous trials have documented their efficacy in controlling blood pressure, minimising left ventricular remodelling, preventing progression to heart failure, ameliorating proteinuria and retarding renal disease progression. Although they are considered safe in general, there remain concerns about the potential for adverse events in certain target populations. Recently, several novel, low molecular weight renin inhibitors without the extended peptide-like backbone of previous renin inhibitors were developed with favourable pharmacokinetic properties. They have been shown to successfully reduce Ang II levels in normal volunteers and to lower blood pressure in patients with mild-to-moderate hypertension. In this review, the authors summarise current knowledge about these renin inhibitors.