FDA has recommended not to co- administer Aliskiren (Tekturna) with Ramipril in patients with diabetes.

 Safety Labeling Changes Approved By FDA CDER 

  http://www.fda.gov/Safety/MedWatch/SafetyInformation/ucm233254.htm

Ramipril is an ACE inhibitor indicated for the treatment of hypertension. It may be used alone or in combination with thiazide diuretics. The most common adverse reactions include headache, dizziness, fatigue, and cough.

Aliskiren is an orally active renin antagonist given in patients with hypertension with elevated plasma renin levels. 

Physicians are advised not to co-administer Aliskiren with Ramipril in patients with diabetes or in patients with renal impairment (GFR < 60 mL/min/1.73 m²).

Dual blockade of the Renin Angiotensin Aldosterone System (RAAS) with ACE inhibitors and Aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy.

Physicians should closely monitor blood pressure, renal functions and electrolytes in patients on Ramipril and other agents that affect the RAAS.