Sildenafil

Sildenafil (brand name(s): Viagra, Kamagra) is a drug used to treat erectile dysfunction.

Risks

You should check the notes in the medication for side effects, different "fillers" for tablets can have different side effects.

If it affects your blood pressure, it can make you feel spaced out and other symptoms (feeling weak, sick blurred vision, fainting), in this case you should stop further sexual and BDSM activities and ensure you are somewhere safe in case you do blackout.

if you have a prolonged or sometimes painful erection, especially if it lasts for more than 2 hours, call emergency services.

Risk Mitigation

Sildenafil should never be used with poppers as together they can cause fatal drop in blood pressure.

It should also not be used in combination with other medicines being used to treat blood pressure.

If you are feeling symptoms of low blood pressure, you should ensure you:

• Seek medical attention
• Lay down
  • Sitting up or standing up suddenly can worsen lightheadedness or cause fainting.
• Drink water
• Do not consume alcohol or other substances

References

https://www.nhs.uk/conditions/low-blood-pressure-hypotension/