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.


METHODS
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 The tizanidine and all of the antihypertensive medications were withdrawn.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.


CONCLUSIONS
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.
Kao
Chuen-Der
CD
Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan.
Chang
Jiun-Bin
JB
Chen
Jen-Tse
JT
Wu
Zin-An
ZA
Shan
Din-E
DE
Liao
Kwong-Kum
KK
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000009:adverse effects*; D003000:Clonidine / Q000009:adverse effects* / Q000031:analogs & derivatives*; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced*; D017706:Lisinopril / Q000009:adverse effects*; D008875:Middle Aged
D000806:Angiotensin-Converting Enzyme Inhibitors; C023754:tizanidine; D017706:Lisinopril; D003000:Clonidine