IN OPHTHALMOLOGY, PHENYLEPHRINE HYDROCHLORIDE IS USED AS A MYDRIATIC IN CONCENTRATIONS OF UP TO 10%; GENERALLY SOLUTIONS CONTAINING 2.5 OR 10% ARE USED BUT SYSTEMIC ABSORPTION CAN OCCUR AND THE 10% STRENGTH, IN PARTICULAR, SHOULD BE USED WITH CAUTION. THE MYDRIATIC EFFECT CAN LAST SEVERAL HOURS. SOLUTIONS CONTAINING 2.5% OR MORE MAY CAUSE INTENSE IRRITATION AND A LOCAL ANAESTHETIC OTHER THAN BUTACAINE (WHICH IS INCOMPATIBLE) SHOULD BE INSTILLED INTO THE EYE A FEW MINUTES BEFOREHAND.
OCULAR SOLUTIONS CONTAINING LOWER CONCENTRATIONS (USUALLY 0.12% PHENYLEPHRINE HYDROCHLORIDE) ARE USED AS A CONJUNCTIVAL DECONGESTANT .
PHENYLEPHRINE HAS BEEN USED PARENTERALLY IN THE TREATMENT OF HYPOTENSIVE STATES, SUCH AS THOSE ENCOUNTERED DURING CIRCULATORY FAILURE OR SPINAL ANAESTHESIA. PHENYLEPHRINE HAS ALSO BEEN USED IN ORTHOSTATIC HYPOTENSION .FOR HYPOTENSION, AN INITIAL DOSE OF PHENYLEPHRINE HYDROCHLORIDE 2 TO 5 MG MAY BE GIVEN AS A 1% SOLUTION SUBCUTANEOUSLY OR INTRAMUSCULARLY WITH FURTHER DOSES OF 1 TO 10 MG IF NECESSARY, ACCORDING TO RESPONSE. A DOSE OF 100 TO 500 MICROGRAMS BY SLOW INTRAVENOUS INJECTION AS A 0.1% SOLUTION, REPEATED AS NECESSARY AFTER AT LEAST 15 MINUTES, HAS ALSO BEEN USED. IN SEVERE HYPOTENSIVE STATES, 10 MG IN 500 ML OF GLUCOSE 5% OR SODIUM CHLORIDE 0.9% HAS BEEN INFUSED INTRAVENOUSLY, INITIALLY AT A RATE OF UP TO 180 MICROGRAMS/MINUTE, REDUCED, ACCORDING TO THE RESPONSE, TO 30 TO 60 MICROGRAMS/MINUTE. FOR CHILDREN AGED 1 TO 12 YEARS, THE BNFC STATES THAT PHENYLEPHRINE MAY BE GIVEN SUBCUTANEOUSLY OR INTRAMUSCULARLY IN A DOSE OF 100 MICROGRAMS/KG EVERY 1 TO 2 HOURS AS NEEDED, TO A MAXIMUM DOSE OF 5 MG. ALTHOUGH THE INTRAVENOUS ROUTE IS NOT LICENSED FOR SUCH USE IN CHILDREN, INTRAVENOUS INJECTION IS PREFERRED TO THE OTHER PARENTERAL ROUTES; FOR CHILDREN AGED 1 TO 12 YEARS, THE DOSE IS 5 TO 20 MICROGRAMS/KG (MAXIMUM 500 MICROGRAMS), REPEATED AS NEEDED AFTER AT LEAST 15 MINUTES. CHILDREN AGED 12 YEARS AND ABOVE ARE GIVEN SIMILAR DOSES TO ADULTS. FOR INTRAVENOUS INFUSION, THOSE AGED 1 TO 16 YEARS MAY BE GIVEN 100 TO 500 NANOGRAMS/KG PER MINUTE, ADJUSTED ACCORDING TO RESPONSE; PHENYLEPHRINE IS DILUTED AS FOR ADULTS (TO A CONCENTRATION OF 20 MICROGRAMS/ML).
PHENYLEPHRINE HYDROCHLORIDE HAS BEEN GIVEN BY INTRAVENOUS INJECTION TO STOP PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA BUT OTHER DRUGS ARE PREFERRED.THE INITIAL DOSE IS USUALLY NOT GREATER THAN 500 MICROGRAMS GIVEN AS A 0.1% SOLUTION WITH SUBSEQUENT DOSES GRADUALLY INCREASED IN INCREMENTS OF 100 TO 200 MICROGRAMS UP TO 1 MG IF NECESSARY.
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