While taking daily dosage of 18mg increasing to 20mg after 4 days...

While taking daily dosage of 18mg increasing to 20mg after 4 days (regular increase of 2mg) I experienced a sudden blackout lasting approx. 5 minutes. I am 58 years of age and had never passed out before. The reason was bradycardia and a drop in BP, from a norm of around 125/85 to 95/58. BP and pulse rate normalised in four days but dosage not increased since. No benefit yet found in dosage of 20mg. Slight nausea and insomnia also experienced. Wondering if I should continue; following advice of GP but would really prefer a homeoepathic remedy if there were one available! Sincerely, Rita Hudd