Question for cardiologists?

Question

is it true that tachycardia might occur with phenobarbital overdose and what type of reaction might that be? I've visited the rx.com web site on phenobarbital and it mentioned it in the overdose section of that web page?

Answer 1

An overdose of Phenobarbital or other barbiturate can cause severe respiratory and cardiovascular depression that resembles shock. An overdose leads to these symptoms because the drug acts on inhibitory receptors(GABA-gamma amino butyric acid) at multiple sites including the brain stem which controls baseline functions such as respiratory drive and vasomotor control(blood vessels). So, as with cardiovascular shock, you will see a significant drop in blood pressure which, when due to barbiturate od is due to severe myocardial(heart muscle) depression and vasomotor instability. The drop in blood pressure along with poor respiration causes the heart rate to increase to the point of tachycardia in an attempt to maintain circulation to the body and oxygenation of tissues.