Details of Drug Interaction | MecDDI

Drug General Information (ID: DDIFO7REXP)
Drug Name			Tizanidine		Drug Info		Isosorbide mononitrate		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Analgesics				Vasodilator Agents
Structure

Mechanism of Tizanidine-Isosorbide mononitrate Interaction (Severity Level: Major)
Additive hypotensive effects Click to Show/Hide Mechanism Graph

Drug Name		Tizanidine				Isosorbide mononitrate
Mechanism		Hypotensive effects Alpha-2 adrenergic receptor Agonist				Hypotensive effects Guanylate cyclase Agonist
Key Mechanism Factor 1
		Factor Name		Adrenergic receptor alpha-2				Structure Sequence
		Protein Family		G-protein coupled receptor 1 family
		Protein Function		Alpha-2 adrenergic receptors mediate the catecholamine-induced inhibition of adenylate cyclase through the action of G proteins. The rank order of potency for agonists of this receptor is oxymetazoline > clonidine > epinephrine > norepinephrine > phenylephrine > dopamine > p-synephrine > p-tyramine > serotonin = p-octopamine. For antagonists, the rank order is yohimbine > phentolamine = mianserine > chlorpromazine = spiperone = prazosin > propanolol > alprenolol = pindolol. Click to Show/Hide
Key Mechanism Factor 2
		Factor Name		Guanylate cyclase soluble				Structure Sequence
		Protein Family		Adenylyl cyclase class-4/guanylyl cyclase family
		Protein Function		There are two types of guanylate cyclases: soluble forms and membrane-associated receptor forms. Activated by nitric oxide in the presence of magnesium or manganese ions. Click to Show/Hide
Mechanism Description		Additive hypotensive effects by the combination of Tizanidine and Isosorbide mononitrate

Recommended Action
Management		A lower initial dosage and cautious dosage titration should be considered when tizanidine is initiated in patients receiving hypotensive medications. Although single doses of less than 8 mg of tizanidine have not been shown effective for spasticity in controlled clinical studies, it may be prudent to initiate treatment with 4 mg doses and gradually increase in 2 to 4 mg increments until optimum effect is achieved. The dose can be repeated at 6 to 8 hour intervals as needed, up to a maximum of three doses in 24 hours and a total daily dosage of 36 mg. However, experience with single doses exceeding 8 mg and daily doses exceeding 24 mg is limited. Close monitoring for development of hypotension is recommended.

References
1	Product Information. Zanaflex (tizanidine). Acorda Therapeutics, Hawthorne, NY.