The effects of sildenafil on the cardiovascular response in men with spinal cord injury at or above the sixth thoracic level.
BACKGROUND
Sildenafil is efficacious for erectile dysfunction in men with spinal cord injury (SCI), but can induce hypotension in neurologically intact people. Those with SCI at or above the sixth thoracic level (T6) often have pre-existing hypotension, yet the cardiovascular response to sildenafil has not been studied in this group.


OBJECTIVE
To evaluate the effect of sildenafil on the cardiovascular response in men with complete SCI at or above T6.


METHODS
This was a randomized, double-blind, placebo-controlled, cross-over study. Twenty-three SCI participants were each randomly given placebo; sildenafil, 50 mg; and sildenafil, 100 mg; separated by at least 1 week. The following were measured before administration, and hourly for 4 hours afterward: (a) blood pressure (BP) and heart rate (HR), both supine and sitting; and (b) perceived dizziness on a visual analog scale upon sitting.


RESULTS
Analysis was done using a 4-way repeated-measures analysis of variance. No significant changes occurred with placebo. Sildenafil caused the following changes. Systolic BP changed little in thoracic spinal cord-injured (TSCI) participants, but decreased significantly (P < 0.005) in cervical spinal cord-injured (CSCI) participants. Diastolic BP decreased in all participants (P < 0.005). HR increased in the TSCI participants for 1 hour (P < 0.05), but was not altered in the CSCI participants. Dizziness increased in the TSCI participants after administration of 100 mg (P < 0.05) and in the CSCI participants after administration of 50 mg (P < 0.05). There were no adverse events or outcomes.


CONCLUSIONS
Sildenafil induces significant hypotension in people with cervical-level injuries--more so than in thoracic-level injuries--and can cause dizziness in both populations. It should be prescribed with caution and informed consent from the patient.
Ethans
Karen D
KD
Health Sciences Centre, Winnipeg, Manitoba, Canada. kethans@hsc.mb.ca
Casey
Alan R
AR
Schryvers
Orpha I
OI
MacNeil
Brian J
BJ
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D002574:Cervical Vertebrae; D018592:Cross-Over Studies; D004244:Dizziness / Q000139:chemically induced*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D011187:Posture / Q000502:physiology; D011687:Purines; D000068677:Sildenafil Citrate; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013450:Sulfones; D013904:Thoracic Vertebrae; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*
D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate