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.

CONCLUSION

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.