Generality
Phenylephrine is an active ingredient with a sympathomimetic action . More specifically, it is an alpha-1 adrenergic receptor agonist .
Thanks to this characteristic, phenylephrine is able to induce vasoconstriction by exercising - depending on the route through which it is administered - an anti-hypotensive action, a mydriatic action, or a decongestant action at the level of the nasal mucosa. Not surprisingly, phenylephrine is included in the composition of numerous medicines (even without a prescription for a medical prescription or a prescription) indicated for the symptomatic treatment of colds and flu.
Also known as " neo-sinephrine ", phenylephrine is available in pharmaceutical forms suitable for parenteral administration, orally, nasally and ocularly .
Examples of Specialties Medicinal products containing Phenylephrine
- Phenylephrine Aguettant®
- Kofidec®
- Nasomixin®
- Onidra®
- Tachifludec®
Therapeutic indications
When is the use of phenylephrine indicated?
The therapeutic indications of phenylephrine vary according to the pharmaceutical form in which the active principle is found, consequently, they also vary according to the route of administration through which the drug is taken.
Phenylephrine administered orally or nasally
Phenylephrine-based medicines to be administered orally and nasally are indicated for the treatment of nasal congestion, especially but not exclusively, in the presence of colds and flu states .
Phenylephrine administered via the eye
Phenylephrine to be administered via the eye is indicated to perform intraocular irrigations in order to dilate the pupil within surgical eye operations (intraocular lens implantation).
Did you know that ...
Generally, inside the medicines to be taken orally and used against cold and flu symptoms, phenylephrine is present in association with other active ingredients, such as paracetamol (antipyretic and mild painkiller) and ascorbic acid (or vitamin C, if you prefer, very useful to support the immune system).
At the same time, phenylephrine to be administered via the eye can be found in association with non-steroidal anti-inflammatory active ingredients, such as ketorolac .
Phenylephrine administered parenterally
When phenylephrine is found in pharmaceutical formulations suitable for parenteral administration, it is indicated in the treatment of hypotensive episodes (lowering of blood pressure) that may occur during general anesthesia .
Warnings
Warnings and Precautions for the use of Phenylephrine
Before taking phenylephrine, you should inform your doctor:
- If you have diabetes;
- If you suffer from hyperthyroidism;
- If you are suffering from hypertension, atherosclerosis or other cardiovascular diseases;
- In the presence of reduced blood circulation in the brain;
- If you suffer from narrow-angle glaucoma
Did you know that ...
Prolonged administration of phenylephrine via the nose may cause alterations in nasal mucosa function, inflammation of the inner walls of the nose associated with mucus production (medicated atrophic rhinitis) and reduced efficacy of the administered drug (tachyphylaxis).
In addition to what has been said so far, it should be remembered that the administration of phenylephrine by the eye can hinder the ability to drive vehicles and / or machinery due to visual changes that occur due to the mydriatic effect. Furthermore, the active ingredient administered through any route could give rise to side effects that may hinder the aforementioned capacity.
Pharmacological Interactions
Phenylephrine interactions with other drugs
Phenylephrine should not be taken through any route of administration concomitantly with monoamine oxidase inhibitors, since a similar association can increase the anti-hypotensive action of phenylephrine causing an excessive increase in blood pressure.
Furthermore, phenylephrine should not be administered parenterally in conjunction with drugs such as:
- Dopaminergic agonists derived from ergot (such as lisuride, pergolide, bromocriptine, etc.)
- General inhalation anesthetics;
- Sibutramine (active ingredient used to suppress the sense of appetite);
- Cardioactive glycosides;
- Oxytocin as a drug to induce childbirth;
- Guanethidine (active ingredient of second choice in the treatment of hypertension);
- Quinidine (active ingredient used to treat heart rhythm abnormalities);
- Linezolid (antibiotic active ingredient).
Oral phenylephrine, on the other hand, must be administered with great caution if the patient is being treated with beta-blockers; while it should not be administered in association with:
- Drugs for the treatment of epilepsy;
- Cimetidine (active ingredient used in the treatment of gastric ulcer);
- Rifampicin and chloramphenicol (active ingredients with antibiotic action);
- Cumarinic anticoagulants;
In any case, before taking phenylephrine in any form, it is necessary to inform the doctor if you are taking - or have recently been taken - drugs of any kind, including prescription-free medicines, over-the-counter drugs. herbal and phytotherapeutic products.
Side effects
Side effects caused by the intake of phenylephrine
Like any other drug, phenylephrine can also cause side effects, although not all patients manifest them or manifest them in the same way. In fact, each individual reacts differently to the administration of the active ingredient in question.
However, the main side effects that may occur during or after taking phenylephrine are listed below.
Psychiatric and nervous system disorders
The administration of phenylephrine orally or parenterally could cause the appearance of:
- agitation;
- Confusion;
- Anxiety;
- Excitability;
- Psychotic states;
- Headache;
- Insomnia;
- Nervousness;
- paresthesia;
- Tremor.
Cardiovascular disorders
The intake of phenylephrine orally or by injection could give rise to undesirable effects such as:
- Hypertensive crisis;
- Cerebral hemorrhage;
- Reflex bradycardia;
- Palpitations;
- Tachycardia;
- Cardiac arrhythmias;
- Angina pectoris;
- Myocardial ischemia.
Ocular pathologies
The administration of phenylephrine by the eye could lead to the following side effects:
- Pain or itching;
- Ocular inflammation;
- Conjunctival hyperemia;
- Corneal edema;
- photophobia;
- Blurred vision;
- Foreign body sensation in the eye;
- Increased intraocular pressure.
Furthermore, when phenylephrine is administered orally or by injection, it could cause mydriasis and worsen in case of pre-existing closed angle glaucoma.
Local side effects
When phenylephrine is administered nasally, it can cause the appearance of undesirable local effects, such as inflammation of the mucous membranes and rebound nasal congestion.
Other side effects
Other side effects that may occur following the intake of phenylephrine (especially if administered orally or parenterally) consist of:
- Nausea and / or vomiting;
- Diarrhea;
- Dyspnoea;
- bronchospasm;
- Pulmonary edema;
- Sweating;
- Pallor;
- piloerection;
- Difficulty in urination;
- Urinary retention;
- Skin necrosis with extravasation (parenteral administration).
Finally, remember that, regardless of the route of administration, phenylephrine can cause allergic reactions in sensitive individuals.
Overdose
In the event of excessive doses of phenylephrine, it is possible to experience an overdose which may occur with symptoms such as:
- Hypertension;
- Tachycardia;
- photophobia;
- Intense headache;
- Thoracic oppression;
- Hyperemia and severe central nervous system depression (symptoms that occur mainly in children).
The treatment of phenylephrine overdose is generally symptomatic and supportive . The hypertensive effect induced by the active ingredient can be counteracted by administering alpha-adrenergic receptor antagonist drugs, such as, for example, phentolamine.
However, given the potentially risky side effects for the life of the patient that may occur, in case of an established or presumed overdose of phenylephrine, it is necessary to contact the doctor or the nearest hospital immediately.
Action mechanism
How does Phenylephrine work?
As mentioned, phenylephrine is a drug with sympathomimetic action . More precisely, it acts as an agonist of alpha-1 adrenergic receptors . Thanks to this capacity, phenylephrine is able to cause a constriction in the arterial and venous blood vessels. This vasoconstriction - depending on the route of administration through which the active ingredient is taken - is capable of exerting a nasal decongestant action (via the oral route and via the nose), or an anti-hypotensive action with a consequent increase in blood pressure (via parenteral).
When administered at the ocular level, however, phenylephrine - always acting as an agonist of alpha-1 adrenergic receptors - is able to induce the contraction of the radial muscle of the iris thus exerting a mydriatic effect (dilation of the pupil). Phenylephrine is also capable of inducing vasoconstriction at the level of the conjunctival circulation and in other blood vessels present in the eye to the extent that they are exposed to the active ingredient in question.
Method of use and Posology
How to take Phenylephrine
Phenylephrine is available in pharmaceutical formulations suitable for oral administration (powder for oral solution), for nasal administration (sprays and nasal drops), for ocular administration (concentrate for solution for intraocular irrigation) and for parenteral administration (solution for injection ).
The dosage of active ingredient to be taken must be established by the doctor, however, the doses normally used will be reported below.
Phenylephrine as a nasal decongestant
To obtain the nasal decongestant effect, phenylephrine can be administered directly via the nasal route, or orally. The dosages usually used in this case are:
- Nasal drops: 1-3 drops of drug per nostril, to be administered three to four times a day.
- Nasal spray: 1-2 sprays for each nostril from three to four times a day.
Note : spray and nasal drops should only be used after blowing the nose.
When, on the other hand, phenylephrine is administered orally, the usually recommended dose is 10 mg of phenylephrine hydrochloride (approximately 8.2 mg of phenylephrine) every 4-6 hours, up to a maximum of three times a day.
Phenylephrine as mydriatic
Phenylephrine-based intraocular irrigations used to obtain the mydriatic effect during eye surgery must be performed by the surgeon who will also determine the dosage of active ingredient to be administered.
Phenylephrine against hypotension during general anesthesia
To counteract hypotension when performing surgical operations performed under general anesthesia, phenylephrine must be administered parenterally by the surgeon or medical staff present. The dosage must be established by the physician on an individual basis for each patient.
Pregnancy and breastfeeding
Can Phenylephrine be taken in pregnancy and during lactation?
The administration of phenylephrine in pregnant women and breast-feeding mothers is generally not recommended. However, the doctor may decide to use the drug also in this category of patients if he considers it absolutely necessary and only after a careful evaluation of the relationship between the expected benefits for the mother and the potential risks to the fetus or newborn .
However, under no circumstances should phenylephrine be taken by pregnant women and breast-feeding mothers without the prior consultation of their doctor or gynecologist. In any case, this category of patients must seek the advice of the aforementioned health figures before taking any type of medicine or product.
Contraindications
When Phenylephrine should not be used
The use of phenylephrine is contraindicated:
- In case of known allergy to phenylephrine itself, to any of the associated active ingredients and / or to any of the excipients contained in the medicinal product to be used;
- In patients suffering from severe hypertension or other heart conditions;
- In patients with hyperthyroidism;
- In patients with closed-angle glaucoma;
- In patients who are taking or have recently taken monoamine oxidase inhibitors (MAOIs).
Furthermore, oral phenylephrine intake should be avoided in patients with kidney dysfunction or disease and in patients with diabetes.
Finally, it is recalled that, depending on the medicinal product used, the route of administration through which the drug is to be taken and the concentration of phenylephrine contained, the use of the active ingredient in question could also be contraindicated in children. For more information on this, you should consult your doctor and refer to what is reported on the illustrative leaflet of the phenylephrine-based medicine to be used.
