Phenylephrine interaction

The more useful types of chirally active bonded phases are those based on the cyclodextrins. There are a number of different types available, some of which have both dispersive or polar groups bonded close to the chirally active sites to permit mixed interactions to occur. This emphasizes the basic entropic differences between the two isomers being separated. A range of such products is available from ASTEC Inc. and a separation of the d and / isomers of scopolamine and phenylephrine are shown in figure 4. The separations were carried out on a cyclodextrin bonded phase (CYCLOBOND 1 Ac) that had been acetylated to provide semi-polar interacting groups in close proximity to the chiral centers of the cyclodextrin. The column was 25 cm long, 4.6 mm in diameter and packed with silica based spherical bonded phase particles 5pm in diameter. Most of the columns supplied by ASTEC Inc. have these dimensions and, consequently, provide a... 

Predictable interactions occur between the MAOIs and any amine precursors, or directly or indirectly acting sympathomimetic amines (e.g. the amphetamines, phenylephrine and tyramine). Such interactions can cause pronounced hypertension and, in extreme cases, stroke. 

Phenylephrine, Nasal (Neo-Synephrine Nasal) (OTC) [Vasopressor/Decongestant] Uses Can be used prior to nasal intubation and NG tube insCTtion to reduce bleeding Action a-Adren gic agonist Dose Adults Feds. 1—2 sprays/nostril q4h (usual 0.25%).Caution [C, +/—] HTN, acute pancreatitis, H, coronary Dz, NAG, h5 pCTth5Toidism Contra Bradycardia, arrhythmias Disp Nasal soln (0.125-0.25%) SE Arrh5rthmias, HTN, nasal irritation, dryness, sneezing, HA Interactions May -1- effects OF nitrates EMS Ocular instillation may dilate pupil... 

The chromophore of phenylephrine is not extended but its structure includes a phenolic hydroxyl group. The phenolic group functions as an auxochrome under both acidic and alkaline conditions. Under acidic conditions it has two lone pairs of electrons, which can interact with the benzene ring and under basic conditions it has three. Figure 4.11 shows the bathochromic and hyperchromic shift in the spectrum of phenylephrine, which occurs when 0.1 M NaOH is used as a solvent instead of 0.1 M HCl. Under acidic conditions the X max is at 273 and has an A (1 %, 1 cm) value of 110 and under alkaline conditions the X max is a 292 nm and has an A (1%, 1 cm) value of 182. 

Practitioners should be aware of over-the-counter (OTC) medications and folk or home remedies that patients may be using. Many patients may not consider OTC agents, especially antihistamines and decongestants for hay fever and colds, as drugs. These can affect the autonomic nervous system. OTC preparations can potentially interact with ocular drugs, such as homatropine and phenylephrine, that also influence autonomic functions. 

Unwanted interactions include the loss of the antihypertensive effect of p-blockers when common cold remedies containing ephedrine, phenylpropanolamine or phenylephrine are taken, usually unknown to the doctor their a-adrenoceptor agonist action is unrestrained in the p-blocked patient. 

Most sympathomimetic amines, such as amphetamine, are available only by prescription others such as phenylephrine and pseudoephedrine, which also are reported to interact similarly with MAO inhibitors, are found in most popular non-prescription cold and allergy preparations. It is important that patients being treated with MAO inhibitors avoid using products containing these agents. 

Tricyclic antidepressants act on both presynaptic and postsynaptic neurons, as well as on alpha- and beta-adrenoceptors. Because their principal action is to block the re-uptake of noradrenaline at the presynaptic neuron, they potentiate the hypertensive effects of both directly acting and indirectly acting amines (155,156). The hypertensive effects of phenylephrine are increased by a factor of 2-3, and of noradrenaline by a factor of 4-8. Even the administration of local anesthetics containing noradrenaline as a vasoconstrictor has proven fatal. The types of compound that can produce this interaction and the symptoms that result have been previously reviewed in detail (SEDA-1,11). 

Clinically important, potentially hazardous interactions with albuterol, alpha-blockers, amitriptyline, amoxapine, atenolol, beta-blockers, carteolol, chlorpromazine, clomipramine, cocaine, desipramine, doxepin, ephedra, ergotamine, furazolidone, halothane, imipramine, insulin detemir, MAO inhibitors, metoprolol, nadolol, nortriptyline, oxprenolol, penbutolol, phenelzine, phenoxybenzamine, phenylephrine, pindolol, prazosin, propranolol, protriptyline, sympathomimetics, terbutaline, thioridazine, timolol, tranylcypromine, tricyclic antidepressants, trimipramine, vasopressors... 

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