Index
It is a nasal decongestant that relieves nasal discomfort caused by colds, allergies, and hay fever.
It belongs to a class of medications called Vasopressors and works by reducing the swelling of the blood vessels in the nose.
Phenylephrine relieves symptoms but does not treat the cause of symptoms or speed recovery.
It is the active ingredient in dozens of generic products, including cough medicines for children and over-the-counter medications.
In 2011, the Food and Drug Administration (FDA) issued a safety alert on certain prescription products for cough, cold, and non-approved allergies that contain Phenylephrine in combination with other medications.
These products are currently not approved by the FDA for safety, efficacy, and quality. Therefore it is not common to find them in the market, and they present little distribution.
The FDA asked pharmaceutical companies to stop shipping many of these products for sale in the United States due to concerns about inappropriate use in young children, potentially dangerous combinations of Phenylephrine, and reports of overuse through “release” products. Temporary”.
Warnings
You should not use medicines that contain Fnilefrin if you have used a monoamine oxidase inhibitor (MAOI) in the last 14 days due to a potentially dangerous drug interaction.
You should also ask a doctor if Phenylephrine is safe to use if you have the following conditions:
- Heart disease.
- High blood pressure .
- Diabetes.
- Thyroid disorder.
If you become pregnant while using Phenylephrine, tell your doctor immediately since this medicine can present significant risks to the health of the fetus and the mother.
If your symptoms do not improve within seven days after starting Phenylephrine, or if you have a fever, stop taking the drug and call your doctor.
Combined over-the-counter cough and cold products, including Phenylephrine, can cause serious side effects or death in young children.
Do not give these products to children under four years of age, be careful and carefully follow package instructions for children ages 4 to 11.
Please read the label carefully to ensure it is the right product for a child. Do not give Phenylephrine products that are made for adults to children.
The artificially sweetened liquid medicine may contain phenylalanine. Check the medication label if you have phenylketonuria, a hereditary disorder that causes the accumulation of the amino acid phenylalanine.
Side effects
- Loss of appetite
- Heat, tingling, or redness under your skin
- Restlessness or excitability (especially in children).
- Sleep problems like insomnia.
- Skin rash or itching
Dosage of Phenylephrine
This medicine is available alone and combined with other medications such as tablets, liquids, or dissolution strips by mouth.
It is usually taken every four hours, as needed, and is also available in extended disclosure forms traditionally taken once or twice a day.
Ask your doctor or pharmacist what the best product for your symptoms is.
Follow the instructions on your prescription label or package label.
Take Phenylephrine precisely as directed. Do not take more or less of this medication or take it more often than prescribed by your doctor or indicated on the label.
You should also carefully check the labels of cough and cold products without a prescription before using two or more products simultaneously.
These products may contain the same active ingredients, and taking them together could cause an overdose.
You must keep a written list of all prescription and over-the-counter medications you are taking and any products such as vitamins, minerals, or other dietary supplements.
Take this list with you each time you visit a doctor, a pharmacist, or if you are admitted to a hospital.
Considerations
Dose of Phenylephrine lost or forgotten?
Medicines that contain Phenylephrine are usually taken as needed.
If your doctor has told you to take Phenylephrine regularly, take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue with your regular dosing schedule. Never double to compensate for the forgotten dose.
Pharmacology
Phenylephrine is used as a nasal decongestant and cardiotonic agent. It is a postsynaptic α1 receptor agonist with little effect on the beta receptors of the heart.
Phenylephrine parenteral administration causes an increase in systolic and diastolic pressures, a slight decrease in cardiac output, and a considerable increase in peripheral resistance.
Most vascular beds are contracted, and renal, splanchnic, cutaneous, and limb flows are reduced while coronary blood flow increases.
Felefrin also causes constriction of the pulmonary vessels and increased pulmonary arterial pressure. The vasoconstriction in the respiratory tract mucosa leads to a decrease in edema and more excellent drainage of the sinus cavities.
Mechanism of action
Adrenergic receptors mediate smooth muscle cells’ contraction and hypertrophic growth. The αlfa one receptors are receptors of 7 transmembrane domains coupled to G proteins.
Three subtypes of αlfa1 receptors have been identified, which share approximately 75% homology in their transmembrane domains: α1A (chromosome 8), α1B (chromosome 5), and α1D (chromosome 20). Phenylephrine appears to act similarly in all three receptor subtypes.
The three subtypes of receptors appear to be involved in maintaining vascular tone. The α1A receptor maintains basal vascular tone while the α1B receptor mediates the vasoconstrictive effects of exogenous α1 agonists.
Activation of the α1 receptor activates the Gq proteins, which results in the intracellular stimulation of phospholipases C, A2, and D.
Phenylephrine decreases nasal congestion by acting on α1-adrenergic receptors in the arterioles of the nasal mucosa to produce constriction; this leads to a decrease in edema and more excellent drainage of the sinus cavities.
Absorption
Phenylephrine is completely absorbed after oral administration. It has a reduced bioavailability (compared to pseudoephedrine) after oral administration due to the significant first-pass metabolism in the intestinal wall.
In comparison with intravenous administration, the bioavailability is approximately 38%. Maximum serum concentrations are reached about 0.75 2 hours after oral administration.
Phenylephrine should be administered parenterally to achieve cardiovascular effects. Occasionally, systemic effects are observed after oral inhalation.
Metabolism
This drug undergoes extensive first-pass metabolism in the intestinal wall and an extensive metabolism in the liver.
The union of sulfate, mainly in the intestinal wall, and oxidative metabolism by monoamine oxidase (MAO) represent the central metabolic pathways. The glucuronidation occurs to a lesser extent.
Phenylephrine and its metabolites are excreted mainly in the urine.
Interactions with other drugs
Tetrahydroisoquinoline: may increase the hypertensive activities of Phenylephrine. Pharmaceutical acceptance status: Experimental.
Acebutolol: the risk or severity of side effects may be increased when Phenylephrine is combined with Acebutolol. Pharmaceutical acceptance status: Approved.
Acemetacin: the therapeutic efficacy of Acemetacin may decrease when used in combination with Phenylephrine. Pharmaceutical acceptance status: Approved, Experimental, Research.
Acetaminophen: The serum concentration of Phenylephrine can be increased when combined with paracetamol. Pharmaceutical acceptance status: Approved.
Alfuzosin: can decrease the vasoconstrictive activities of Phenylephrine. Pharmaceutical acceptance status: Approved, under investigation.
Amineptine: may increase phenylephrine vasopressor activities. Pharmaceutical acceptance status: Illegal, withdrawn.
Amitriptyline: may increase phenylephrine vasopressor activities—pharmaceutical acceptance status: Approved.
Amoxapine: may increase phenylephrine vasopressor activities. Pharmaceutical acceptance status: Approved.
Amphetamine: the risk or severity of side effects can be increased when Amphetamine is combined with Phenylephrine. Pharmaceutical acceptance status: Approved, unlawful.
Brofaromina: can increase the hypertensive activities of Phenylephrine. Pharmaceutical acceptance status: Experimental.
Bromocriptine: can increase the hypertensive activities of Phenylephrine. Pharmaceutical acceptance status: Approved, under investigation.
Bucindolol: can decrease the vasoconstrictive activities of Phenylephrine. Pharmaceutical acceptance status: Investigational.
Bunazosin: can decrease the vasoconstrictive activities of Phenylephrine. Pharmaceutical acceptance status: Investigational.
Cabergoline: can increase the hypertensive activities of Phenylephrine. Pharmaceutical acceptance status: Approved.
Calcium carbide: the risk or severity of side effects may increase when calcium carbide is combined with Phenylephrine. Pharmaceutical acceptance status: Withdrawn.
The risk or severity of side effects may increase when Phenylephrine is combined with Celiprolol. Pharmaceutical acceptance status: Approved, under investigation.
Chlorphentermine: the risk or severity of side effects may increase when Phenylephrine is combined with Chlorphentermine. Pharmaceutical acceptance status: Illegal, withdrawn.
Clenbuterol: The risk or severity of side effects can be increased when Phenylephrine is combined with Clenbuterol. Pharmaceutical acceptance status: Approved, under investigation, approved by the veterinarian.
