The principle of action of phenobarbital is related to its activation of gamma-aminobutyric acid (GABA) receptors. Phenobarbital belongs to the barbiturates, and the sedative, hypnotic and anticonvulsant effects of barbiturates are related to their activation of GABA receptors. In the absence of GABA, barbiturates can mimic the effects of GABA, increase the permeability of chloride ions (mainly by prolonging the time of the opening of chloride ion channels), and hyperpolarize the cell membrane. In vitro electrophysiological experiments found that phenobarbital can open the chloride ion channels of nerve cells and hyperpolarize the cells, which has the effect of GABA mimicry; therapeutic concentrations of phenobarbital can enhance the inhibitory effect of GABA, inhibit the monosynaptic and polysynaptic transmission of the central nervous system, and inhibit high-frequency discharges of epileptic foci and their diffusion to the surrounding area. The pharmacological effects of phenobarbital, related to its dosage, with the increase of the dosage of the drug, the patient may experience sedation, hypnosis, anticonvulsant, and even inhibition of inhibition of the medullary respiratory center, leading to respiratory failure, inhibition of the vasomotor center, so that peripheral vasodilatation, the occurrence of shock. Dizziness, drowsiness and other after-effects may occur after the use of the drug, prolonged use may produce dependence and tolerance, and repeated application should be alert to accumulation of poisoning. A small number of allergic reactions such as skin rash and exfoliative dermatitis may occur. The drug needs to be used under the guidance of a doctor, and should not be used blindly on its own to avoid adverse reactions.