Sometimes allergic reactions are possible: skin rash, itching, urticaria, angioedema.
Rarely - from the side of the blood (thrombocytopenia, leukopenia, agranulocytosis); increased intraocular pressure, nausea, vomiting, epigastric pain, urinary retention.
With prolonged use, exceeding the recommended dose, hepatotoxic and nephrotoxic effects may be observed.
Phenylephrine hydrochloride can cause nausea, headache, high blood pressure and, in rare cases, heartbeat that pass after drug withdrawal.