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Phenylephrine
What is phenylephrine?
Phenylephrine is a decongestant. It works by constricting (shrinking) blood vessels (veins and arteries). Constriction of blood vessels in the sinuses, nose, and chest allows drainage of these areas, which decreases congestion. Constriction of blood vessels also affects blood pressure.
When taken by mouth, phenylephrine is used to treat congestion associated with allergies, hay fever, sinus irritation, and the common cold. When used by injection, phenylephrine is used to maintain adequate blood pressure and to treat certain types of irregular heartbeats.
Phenylephrine may also be used for purposes other than those listed in this medication guide.
Precautions
Do not use phenylephrine if you have taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), phenelzine (Nardil), or tranylcypromine (Parnate) in the last 14 days. A dangerous drug interaction leading to serious side effects could occur.
Before using this medication, tell your doctor if you have
- high blood pressure;
- heart disease, hardening of the arteries, or irregular heartbeats;
- thyroid problems;
- diabetes;
- glaucoma or increased pressure in the eye(s);
- an enlarged prostate or difficulty urinating;
- liver disease; or
- kidney disease.
You may not be able to use phenylephrine, or you may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.
Phenylephrine is in the FDA pregnancy category C. This means that it is not known whether it will harm an unborn baby. Do not use this medication without first talking to your doctor if you are pregnant.
Phenylephrine may pass into breast milk and affect a nursing baby. Do not use this medication without first talking to your doctor if you are breast-feeding a baby.
If you are over 60 years of age, you may be more likely to experience side effects from phenylephrine. You may require a lower dose of this medication.
Do not use more of this medication than is recommended on the package or by your doctor. Too much medication could be harmful
Use caution when driving, operating machinery, or performing other hazardous activities. Phenylephrine may cause dizziness, drowsiness, or impaired concentration. If you experience dizziness, drowsiness, or impaired concentration, avoid these activities.
Instructions
Seek emergency medical attention.
Symptoms of a phenylephrine overdose include extreme tiredness, sweating, dizziness, a slow heartbeat, and coma.
Use the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the dose you missed and use only the next regularly scheduled dose.Do not use a double dose of this medication.
Side-effects
If you experience any of the following serious side effects, stop using phenylephrine and seek emergency medical attention or contact your doctor immediately:
- an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
- seizures;
- unusual behavior or hallucinations; or
- an irregular or fast heartbeat.
Other, less serious side effects may be more likely to occur. Continue to take phenylephrine and talk to your doctor if you experience
- dizziness, lightheadedness, or drowsiness;
- headache;
- insomnia;
- anxiety;
- tremor (shaking) or restlessness;
- nausea or vomiting; or
- sweating.
Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or especially bothersome.
Interactions
Do not use phenylephrine if you have taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), phenelzine (Nardil), or tranylcypromine (Parnate) in the last 14 days. A dangerous drug interaction leading to serious side effects could occur.
Before taking phenylephrine, tell your doctor if you are taking any other medicines especially any of the following:
- medicine to treat high blood pressure or a heart condition;
- medicine to treat diabetes;
- weight loss medication;
- another decongestant (cold or allergy product); or
- a tricyclic antidepressants such as amitriptyline (Elavil, Endep), doxepin (Sinequan), amoxapine (Asendin), clomipramine (Anafranil), desipramine (Norpramin), imipramine (Tofranil), protriptyline (Vivactil), trimipramine (Surmontil), or nortriptyline (Pamelor).
You may not be able to take phenylephrine, or you may require a dosage adjustment or special monitoring during treatment if you are taking any of the medicines listed above.
Drugs other than those listed here may also interact with phenylephrine. Talk to your doctor or pharmacist before taking any prescription or over-the-counter medicines, including herbal products.
Disclaimer
Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.
Copyright 1996-2004 Cerner Multum, Inc. Version 2.05. Revision date 8/23/04