Phenylephrine hydrochloride

Description

Phenylephrine is an alpha-1 adrenergic receptor agonist. Phenylephrine hydrochloride Injection, 10 mg/mL, is a clear, colorless, sterile, non-pyrogenic solution intended for intravenous use. Prior to administration, it must be diluted for either intravenous bolus or continuous intravenous infusion. The chemical name of phenylephrine hydrochloride is (-)-m-hydroxy-α-(methylamino)methyl benzyl alcohol hydrochloride, with a chemical designation of C9H14ClNO2 and a molecular weight of 203.66 g/mol.

Phenylephrine hydrochloride is soluble in water and ethanol, but insoluble in chloroform and ethyl ether. The injection is sensitive to light. Each mL of the solution contains 10 mg of phenylephrine hydrochloride, 3.5 mg of sodium chloride, 4 mg of sodium citrate dihydrate, 1 mg of citric acid monohydrate, and 2 mg of sodium metabisulfite, all in water for injection. The pH of the solution is adjusted with sodium hydroxide and/or hydrochloric acid as necessary, maintaining a pH range of 3.5-5.5. The structural formula is depicted below.

Uses and Indications

Phenylephrine hydrochloride Injection is indicated for the treatment of clinically important hypotension resulting primarily from vasodilation in the setting of anesthesia.

There are no teratogenic or nonteratogenic effects associated with this drug.

Dosage and Administration

Phenylephrine hydrochloride Injection, 10 mg/mL, is administered intravenously either as a bolus injection or as a continuous infusion. Prior to administration, the solution must be diluted.

For the treatment of hypotension during anesthesia, the following dosing guidelines are recommended:

Bolus Intravenous Injection: Administer 40 mcg to 100 mcg every 1 to 2 minutes as needed. The total dose should not exceed 200 mcg.

Intravenous Infusion: Initiate at a rate of 10 mcg/min to 35 mcg/min, adjusting the infusion rate based on the patient's pressor response. The infusion rate should not exceed 200 mcg/min.

Healthcare professionals should titrate the dose to achieve the desired effect, ensuring careful monitoring of the patient's response throughout the administration.

Contraindications

There are no contraindications associated with the use of this product. It is not classified as a controlled substance, and there are no identified risks of abuse, misuse, or dependence.

Warnings and Precautions

Phenylephrine hydrochloride is associated with several significant warnings and precautions that healthcare professionals must consider to ensure patient safety.

Cardiovascular Risks Phenylephrine hydrochloride may exacerbate angina in patients with severe arteriosclerosis or a history of angina. It is crucial to monitor patients for signs of angina and to assess their cardiovascular status regularly. Additionally, this medication can worsen underlying heart failure and elevate pulmonary arterial pressure, necessitating careful evaluation of patients with pre-existing heart conditions.

Ischemic Events The use of phenylephrine hydrochloride can lead to excessive peripheral and visceral vasoconstriction, resulting in ischemia to vital organs. Healthcare providers should be vigilant in monitoring for symptoms of ischemia, particularly in patients with compromised vascular health.

Tissue Necrosis Extravasation during intravenous administration of phenylephrine hydrochloride poses a risk of skin and subcutaneous necrosis. It is imperative to ensure proper intravenous technique and to monitor the injection site closely for any signs of extravasation, which may necessitate immediate intervention to prevent tissue damage.

Bradycardia Phenylephrine hydrochloride has the potential to induce severe bradycardia and decrease cardiac output. Continuous cardiac monitoring is recommended for patients receiving this medication, particularly those with existing bradycardia or other cardiac conditions.

Healthcare professionals should remain alert to these risks and implement appropriate monitoring strategies to mitigate potential adverse effects associated with phenylephrine hydrochloride.

Side Effects

Patients receiving phenylephrine hydrochloride may experience a range of adverse reactions. The most commonly reported adverse reactions include nausea, vomiting, and headache.

Serious side effects associated with phenylephrine hydrochloride include exacerbation of angina, heart failure, or pulmonary arterial hypertension. This medication can precipitate angina in patients with severe arteriosclerosis or a history of angina, exacerbate underlying heart failure, and increase pulmonary arterial pressure. Additionally, excessive peripheral and visceral vasoconstriction may lead to ischemia of vital organs. Extravasation during intravenous administration has been reported to cause skin and subcutaneous necrosis, resulting in necrosis or sloughing of tissue. Severe bradycardia and decreased cardiac output are also potential serious adverse effects.

In cases of overdose, patients may experience a rapid rise in blood pressure, with symptoms including headache, vomiting, hypertension, reflex bradycardia, a sensation of fullness in the head, tingling of the extremities, and cardiac arrhythmias such as ventricular extrasystoles and ventricular tachycardia.

No additional adverse reactions or important notes have been identified.

Drug Interactions

Agonistic interactions that may enhance the blood pressure effects of Phenylephrine hydrochloride are observed with several drug classes. These include monoamine oxidase inhibitors (MAOIs), oxytocin and oxytocic drugs, tricyclic antidepressants, angiotensin and aldosterone, atropine, steroids, norepinephrine transporter inhibitors, and ergot alkaloids. Clinicians should monitor blood pressure closely when these agents are co-administered with Phenylephrine hydrochloride, as dosage adjustments may be necessary to avoid excessive hypertension.

Conversely, antagonistic interactions that may diminish the blood pressure effects of Phenylephrine hydrochloride can occur with α-adrenergic antagonists, phosphodiesterase Type 5 inhibitors, mixed α- and β-receptor antagonists, calcium channel blockers, benzodiazepines, ACE inhibitors, and centrally acting sympatholytic agents. It is advisable to assess blood pressure regularly in patients receiving these medications concurrently with Phenylephrine hydrochloride, as this may necessitate adjustments in dosing or therapeutic strategy to achieve the desired hemodynamic response.

Packaging & NDC

The table below lists all NDC Code configurations of Phenylephrine Hydrochloride, the U.S. brand-name prescription product. Columns show Packaging, Formulation Type, and Active Ingredient Strength.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established. Therefore, the use of this medication in children, infants, and adolescents should be approached with caution until further data is available.

Geriatric Use

Clinical studies of phenylephrine did not include a sufficient number of subjects aged 65 and over to determine whether they respond differently from younger subjects. However, other reported clinical experience has not identified significant differences in responses between elderly patients and younger patients.

In general, dose selection for geriatric patients should be approached with caution. It is advisable to start at the low end of the dosing range, taking into account the increased likelihood of decreased hepatic, renal, or cardiac function, as well as the presence of concomitant diseases or other drug therapies. Careful monitoring of these patients is recommended to ensure safety and efficacy.

Pregnancy

Data from randomized controlled trials and meta-analyses involving the use of phenylephrine hydrochloride injection in pregnant women during Cesarean sections have not established a drug-associated risk of major birth defects or miscarriage. These studies have not identified any adverse effects on maternal outcomes or infant Apgar scores. However, there are no data available regarding the use of phenylephrine during the first or second trimester of pregnancy.

Animal reproduction and development studies have shown evidence of fetal malformations when phenylephrine was administered during organogenesis via a 1-hour infusion at a dose of 1.2 times the human daily dose (HDD) of 10 mg/60 kg/day. Additionally, decreased pup weights were observed in offspring of pregnant rats treated with 2.9 times the HDD. It is important to note that the estimated background risk of major birth defects and miscarriage for the indicated population remains unknown, although all pregnancies carry a background risk of birth defects, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is approximately 2-4% and 15-20%, respectively.

Untreated hypotension associated with spinal anesthesia during Cesarean sections can lead to increased maternal nausea and vomiting. A sustained decrease in uterine blood flow due to maternal hypotension may result in fetal bradycardia and acidosis. Published randomized controlled trials over several decades comparing phenylephrine injection to other similar agents in pregnant women during Cesarean sections have not identified any adverse maternal or infant outcomes. At recommended doses, phenylephrine does not appear to significantly affect fetal heart rate or fetal heart rate variability.

There are no studies assessing the safety of phenylephrine injection exposure during the period of organogenesis, making it impossible to draw conclusions regarding the risk of birth defects following exposure during pregnancy. Furthermore, there are no data available on the risk of miscarriage following fetal exposure to phenylephrine injection.

In studies involving normotensive pregnant rabbits, no clear malformations or fetal toxicity were reported when treated with phenylephrine via continuous intravenous infusion over 1 hour at a dose of 0.5 mg/kg/day (approximately equivalent to a HDD based on body surface area) from Gestation Day 7 to 19. This dose, which did not demonstrate maternal toxicity, was associated with evidence of developmental delay (altered ossification of sternebra). However, in a non-GLP dose range-finding study, fetal lethality and cranial, paw, and limb malformations were noted following treatment with 1.2 mg/kg/day of phenylephrine, which was clearly maternally toxic. An increase in the incidence of limb malformation was observed at a lower dose of 0.6 mg/kg/day in the absence of maternal toxicity.

In contrast, no malformations or embryo-fetal toxicity were reported in normotensive pregnant rats treated with up to 3 mg/kg/day of phenylephrine, although this dose was associated with some maternal toxicity. Decreased pup weights were noted in a pre-and postnatal development toxicity study involving normotensive pregnant rats administered phenylephrine from Gestation Day 6 through Lactation Day 21. Importantly, no adverse effects on growth and development (including learning and memory, sexual development, and fertility) were observed in the offspring of pregnant rats at any tested dose. Maternal toxicities, including mortality late in gestation and during the lactation period, as well as decreased food consumption and body weight, occurred at doses of 1 and 3 mg/kg/day of phenylephrine.

Lactation

There are no data on the presence of phenylephrine hydrochloride injection or its metabolite in human or animal milk, nor are there any known effects on the breastfed infant or on milk production.

Healthcare professionals should consider the developmental and health benefits of breastfeeding alongside the clinical need for phenylephrine hydrochloride in lactating mothers. Additionally, potential adverse effects on the breastfed infant from either phenylephrine hydrochloride or the underlying maternal condition should be taken into account when making treatment decisions.

Renal Impairment

There is no specific information regarding dosage adjustments, special monitoring, or safety considerations for patients with renal impairment. Healthcare professionals should exercise caution when prescribing to patients with reduced kidney function, as the absence of detailed guidance necessitates careful clinical judgment. Regular monitoring of renal function may be advisable in this patient population.

Hepatic Impairment

Patients with hepatic impairment have not been specifically studied in relation to the use of this medication. Consequently, there are no established dosage adjustments, special monitoring requirements, or precautions for individuals with compromised liver function. It is recommended that healthcare providers exercise caution when prescribing this medication to patients with hepatic impairment, given the lack of data on its safety and efficacy in this population. Regular monitoring of liver function may be prudent in these cases, although specific parameters are not defined in the available information.

Overdosage

In cases of phenylephrine hydrochloride overdose, a rapid increase in blood pressure is a significant concern. Healthcare professionals should be vigilant for a range of symptoms that may manifest following an overdose.

Symptoms of Overdosage Patients may experience a variety of symptoms, including but not limited to:

• Headache

• Vomiting

• Hypertension

• Reflex bradycardia

• A sensation of fullness in the head

• Tingling of the extremities

• Cardiac arrhythmias, which may include ventricular extrasystoles and ventricular tachycardia

Management Procedures In the event of an overdose, immediate medical intervention is recommended. Monitoring of blood pressure and cardiac function is essential. Appropriate measures should be taken to manage hypertension and any arrhythmias that may arise. Supportive care should be provided as necessary, and symptomatic treatment should be initiated based on the clinical presentation of the patient.

Healthcare professionals are advised to follow established protocols for the management of drug overdoses, ensuring that all interventions are tailored to the individual patient's needs.

Nonclinical Toxicology

Long-term animal studies conducted by the National Toxicology Program evaluated the carcinogenic potential of orally administered phenylephrine hydrochloride in F344/N rats and B6C3F1 mice. These studies utilized the dietary route of administration and found no evidence of carcinogenicity in mice receiving approximately 270 mg/kg/day, which is 131 times the human daily dose (HDD) of 10 mg/60 kg/day based on body surface area. Similarly, rats administered approximately 50 mg/kg/day, equivalent to 48 times the HDD, also showed no signs of carcinogenicity.

Phenylephrine hydrochloride was tested for mutagenicity and yielded negative results in several assays, including the in vitro bacterial reverse mutation assay (S. typhimurium strains TA98, TA100, TA1535, and TA1537), the in vitro chromosomal aberrations assay, the in vitro sister chromatid exchange assay, and the in vivo rat micronucleus assay. However, positive results were observed in one of two replicates of the in vitro mouse lymphoma assay.

In terms of reproductive toxicity, phenylephrine did not impair mating, fertility, or reproductive outcomes in normotensive male rats treated with 3 mg/kg/day via continuous intravenous infusion over 1 hour (2.9 times the HDD) for 28 days prior to mating and for a minimum of 63 days prior to sacrifice. Female rats received the same dosing regimen for 14 days prior to mating and continued through Gestation Day 6. It is important to note that this dose was associated with increased mortality in both male and female rats, as well as decreased body weight gain in treated males. Additionally, males treated with 3 mg/kg/day phenylephrine exhibited decreased caudal sperm density and an increase in abnormal sperm.

Postmarketing Experience

Postmarketing experience has identified several adverse reactions associated with the use of the product. These include hypertension, reflex bradycardia, and arrhythmias. Additional adverse reactions reported include headache, anxiety, and nausea.

There have been cases of extravasation leading to tissue necrosis, as well as reports of severe allergic reactions, including anaphylaxis. Furthermore, some patients experienced elevated blood pressure and heart rate during treatment.

Patient Counseling

Healthcare providers should inform patients, as well as their family members or caregivers, that certain medical conditions and medications may affect the efficacy of phenylephrine hydrochloride injection. It is important to discuss any pre-existing health issues or ongoing treatments that the patient may have, as these factors could influence the response to the medication.

Providers are encouraged to ensure that patients understand the significance of sharing their complete medical history and current medication regimen, including over-the-counter drugs and supplements, to facilitate safe and effective use of phenylephrine hydrochloride injection.

Storage and Handling

Phenylephrine hydrochloride Injection, 10 mg/mL is supplied in 1 mL vials designated for single use only, as well as in 5 mL and 10 mL vials which are intended as pharmacy bulk packages.

This product should be stored at a temperature range of 20°C to 25°C (68°F to 77°F), with permissible excursions between 15°C to 30°C (59°F to 86°F). It is essential to protect the vials from light and to keep them in their original carton until they are ready for use.

Once diluted, the solution must not be held for more than 4 hours at room temperature or for more than 24 hours when refrigerated. Any unused portion should be discarded to ensure safety and efficacy.

Additional Clinical Information

No further data are available.

FDA Insert (PDF)

This document is the official FDA-approved prescribing information for Phenylephrine Hydrochloride as submitted by Armas Pharmaceuticals Inc.. It includes detailed information about indications, dosage, contraindications, warnings, and clinical pharmacology.

View full prescribing information (PDF)