Muscle Relaxers

Question 1

What is cyclobenzaprine for?

Answer 1

Muscle spasm generic oral drug, related to amitriptyline, ineffective for pain 2ndary to cerebral or spinal cord dz; also used off label in FM

Question 2

Cyclobenzaprine MOA?

Answer 2

Central action, maybe at brainstem?

Question 3

Cyclobenzaprine met/elim?

Answer 3

Enterohepatic recirculation and CYP3A4, 1A2, and 2D6; caution in liver failure

Question 4

Cyclobenzaprine ADE’s?

Answer 4

Anticholinergic = opposite of SLUDGEBBB that are additive with other anti-cholindergics (GI=paralytic ileum). CNS depression/drowsiness. QT prolongation

Question 5

Tizanidine use?

Answer 5

Oral for MS, Spasticity, and spinal cord trauma

Question 6

Tizanidine MOA?

Answer 6

Agonist of presynaptic a2 receptors = decrease activation of polysynaptic motor neurons and reduction in motor tone (not strength!); similar to clonidine but clonidine is mostly relaxation of vasc smooth muscle and Tizanidine only had 10% vascular potency compared to clonidine

Question 7

Tizanidine met/elim?

Answer 7

Extensive FP; short half life; renal elim of long lasting metabolites; titrate to effect with renal deficiency

Question 8

Tizanidine ADEs?

Answer 8

Hepatits, rebound hypertonicity in muscle or rebound tachycardia/HTN, additive CNS depression, additive hypotension, asthenia, and xerostomia

Question 9

Tizanidine monitoring?

Answer 9

LFTs