Phenylephrine Insulin

These compounds include NE, which acts on both a and P receptors, and epinephrine, which is more active on p receptors. As mentioned previously, catecholamines lacking a 4-OH group, such as phenylephrine (4.47) and methoxamine (4.48), show almost pure a, activity. They are both vasoconstrictors, used in treating hypotension (low blood pressure) and nasal congestion. These drugs may also inhibit insulin release. 

Use phenylephrine 10% with caution in patients with cardiac disease, idiopathic orthostatic hypotension, hypertension, aneurysms, insulin-dependent diabetes, and advanced arteriosclerosis. 

Contraindications to the topical use of hydroxyamphetamine for routine mydriasis are similar to those to phenylephrine. Because of its tachyphylaxis and ineffectiveness in postganglionic denervation, however, hydroxyamphetamine may be a safer mydriatic for use in patients with insulin-dependent diabetes, idiopathic orthostatic hypotension, or chemical sympathectomy produced by therapy with systemic guanethidine, reserpine, or methyl-dopa. Thus hydroxyamphetamine seems to be less strongly contraindicated than phenylephrine for certain high-risk patients. 

A significant loss of insulin activity occurred when solutions of amorphous insulin were exposed to ultraviolet radiation (1). The ultraviolet irradiation of phenylephrine HCl results in the formation of a product with demonstrated bronchodilator potency greater than that of the original solution, when tested on perfused guinea pig lungs (2). A solution of epinephrine exposed to radiation from a quartz mercury burner for 35 minutes was reported to produce practically no pressor, but depressor action, when tested on an anesthetized dog. However, the nonirradiated solution produced a marked pressor action with little depressor effect (3). 

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... 

Type 1 (insulin-dependent) diabetics can develop elevated blood pressures if they are given phenylephrine eye drops. 

A 49-year-old woman with diabetes and hypertension took a deliberate overdose of 60 tablets containing metformin 500 mg and about 25 tablets of hydrochlorothiazide/lisinopril 12.5/ 20 mg. She was seen and treated within 1 hour. Her pH was 7.18, bicarbonate 6 mmol/1, lactate 9.6 mmol/1, glucose 32 mmol/1, and creatinine 106 (imol/1. Treatment included isotonic saline, sodium bicarbonate, and insulin but 5 hours later her pH was 6.79 and bicarbonate 8.4 mmol/1. Continuous venovenous hemofiltration was begun. Hypotension was treated with noradrenaline, phenylephrine, and then... 

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