Ramipril (an ACE inhibitor antihypertensive drug) can cause hyperkalaemia (high potasium level in the blood) which if left high can cause other problems such as heart abnormal heart rythms.
Another possible side effect of ACE inhibitors is a dry cough.
Stopping the ramipril is a sensible course of action and indicated in hyperkalaemia.
If there is still hyptension then there are other classes of antihypertensives that can be prescribed such as calcium channel blockers, beta blockers, diuretics, alpha blockers.
Additionally you are correct, ramipril has been shown in studies to be less effective in blacks then in caucasians.
I hope this information is useful, feel free to reply for any clarification
The diastolic blood pressure is on the high side. However it is wise to have this monitored by your GP to advise on treatment.
Ramipril can cause headaches. However this doesn't mean that this was the cause of your headache, as there are multiple possible causes for headache.
The other symptoms you describe are feeling sleepy and sluggish. Again there are lots of possible reasons for this. These can include depression, electrolyte abnormality from the side effects of ramipril which is reversible, hypotension secondary to the ramipril, other possible metabolic abnormalities etc. If you are having lots of stress at the moment this could be giving the headaches, result in night time sleeplessness and daytime sleepiness.
Given these symptoms it would be sensible to see your GP who will most likely perform a neuro exam and screen for depression. You will also need blood tests to monitor that potassium and renal function to check this returns to normal, rule out anaemia, check thyroid function to rule out hypothyroid, glucose check to rule out diabetes.