Drug in Pharm book NOT FOUND in my drug guides...

  1. Okay, so here I am, happily working away at my Pharmacology workbook (okay, maybe not happily, but working...) and I come across a drug listed that I don't see a drug profile for. No problem, I think, I can just look it up in my handy dandy Mosby's. No drug found. Okay, step two: Look it up in my Davis Drug Guide on my PDA. Not found there either. I can't get ahold of my instructor, and its bugging me to death!

    The drug is called phenoxybenzamine hydrochloride. (and I double checked the spelling). The book says it is an alpha blocker that reduces blood pressure by reducing peripheral vascular resistance, used to treat the hypertension caused by pheochromocytoma.

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    About phoenixfire

    Joined: Dec '06; Posts: 108; Likes: 148
    Student, Mom, Author


  3. by   Jado0114
    My drug book says that it's an Off Market Drug...no longer available in the US. That may be why you can't find it. Do you still need the info on it anyway??
  4. by   midcom
    i always check the internet in this instance.
    here is what i found at http://dailymed.nlm.nih.gov/dailymed...fo.cfm?id=2157
    clinical pharmacology

    dibenzyline (phenoxybenzamine hydrochloride) is a long-acting, adrenergic, alpha-receptor-blocking agent, which can produce and maintain "chemical sympathectomy" by oral administration. it increases blood flow to the skin, mucosa and abdominal viscera, and lowers both supine and erect blood pressures. it has no effect on the parasympathetic system.
    twenty to 30 percent of orally administered phenoxybenzamine appears to be absorbed in the active form.1
    the half-life of orally administered phenoxybenzamine hydrochloride is not known; however, the half-life of intravenously administered drug is approximately 24 hours. demonstrable effects with intravenous administration persist for at least 3 to 4 days, and the effects of daily administration are cumulative for nearly a week.1

    indication and usage

    dibenzyline is indicated in the treatment of pheochromocytoma, to control episodes of hypertension and sweating. if tachycardia is excessive, it may be necessary to use a beta-blocking agent concomitantly.


    conditions where a fall in blood pressure may be undesirable; hypersensitivity to the drug or any of its components.


    dibenzyline-induced alpha-adrenergic blockade leaves beta-adrenergic receptors unopposed. compounds that stimulate both types of receptors may, therefore, produce an exaggerated hypotensive response and tachycardia.


    general−administer with caution in patients with marked cerebral or coronary arteriosclerosis or renal damage. adrenergic blocking effect may aggravate symptoms of respiratory infections.
    drug interactions2−dibenzyline (phenoxybenzamine hydrochloride) may interact with compounds that stimulate both alpha- and beta-adrenergic receptors (i.e., epinephrine) to produce an exaggerated hypotensive response and tachycardia.(see warning.)
    dibenzyline blocks hyperthermia production by levarterenol, and blocks hypothermia production by reserpine.

    carcinogenesis and mutagenesis

    phenoxybenzamine hydrochloride showed in vitro mutagenic activity in the ames test and mouse lymphoma assay; it did not show mutagenic activity in vivo in the micronucleus test in mice. in rats and mice, repeated intraperitoneal administration of phenoxybenzamine hydrochloride (three times per week for up to 52 weeks) resulted in peritoneal sarcomas. chronic oral dosing in rats (for up to 2 years) produced malignant tumors of the small intestine and non-glandular stomach, as well as ulcerative and/or erosive gastritis of the glandular stomach. whereas squamous cell carcinomas of the non-glandular stomach were observed at all tested doses of phenoxybenzamine hydrochloride, there was a no observed effect level of 10 mg/kg for tumors (carcinomas and sarcomas) of the small intestine. this dose is, on a body surface area basis, about twice the maximum recommended human dosage of 20 mg b.i.d.


    teratogenic effects

    pregnancy category c. adequate reproductive studies in animals have not been performed with dibenzyline (phenoxybenzamine hydrochloride). it is also not known whether dibenzyline can cause fetal harm when administered to a pregnant woman. dibenzyline should be given to a pregnant woman only if clearly needed.

    nursing mothers

    it is not known whether this drug is excreted in human milk. because many drugs are excreted in human milk, and because of the potential for serious adverse reactions from phenoxybenzamine hydrochloride, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

    pediatric use

    safety and effectiveness in pediatric patients have not been established.

    adverse reactions

    the following adverse reactions have been observed, but there are insufficient data to support an estimate of their frequency.

    autonomic nervous system* ostural hypotension, tachycardia, inhibition of ejaculation, nasal congestion, miosis.
    *these so-called "side effects" are actually evidence of adrenergic blockade and vary according to the degree of blockade.

    miscellaneous: gastrointestinal irritation, drowsiness, fatigue.


    symptoms-these are largely the result of blocking of the sympathetic nervous system and of the circulating epinephrine. they may include postural hypotension, resulting in dizziness or fainting; tachycardia, particularly postural; vomiting; lethargy; shock.


    when symptoms and signs of overdosage exist, discontinue the drug. treatment of circulatory failure, if present, is a prime consideration. in cases of mild overdosage, recumbent position with legs elevated usually restores cerebral circulation. in the more severe cases, the usual measures to combat shock should be instituted. usual pressor agents are not effective. epinephrine is contraindicated because it stimulates both alpha- and beta- receptors; since alpha- receptors are blocked, the net effect of epinephrine administration is vasodilation and a further drop in blood pressure (epinephrine reversal).
    the patient may have to be kept flat for 24 hours or more in the case of overdose, as the effect of the drug is prolonged. leg bandages and an abdominal binder may shorten the period of disability.
    i.v. infusion of levarterenol bitartrate ** may be used to combat severe hypotensive reactions, because it stimulates alpha-receptors primarily. although dibenzyline (phenoxybenzamine hydrochloride) is an alpha -adrenergic blocking agent, a sufficient dose of levarterenol bitartrate will overcome this effect.
    the oral ld50 for phenoxybenzamine hydrochloride is approximately 2000 mg/kg in rats and approximately 500 mg/kg in guinea pigs.

    dosage and administration

    the dosage should be adjusted to fit the needs of each patient. small initial doses should be slowly increased until the desired effect is obtained or the side effects from blockade become troublesome. after each increase, the patient should be observed on that level before instituting another increase. the dosage should be carried to a point where symptomatic relief and/or objective improvement are obtained, but not so high that the side effects from blockade become troublesome.
    initially, 10 mg of dibenzyline (phenoxybenzamine hydrochloride) twice a day. dosage should be increased every other day, usually to 20 to 40 mg 2 or 3 times a day, until an optimal dosage is obtained, as judged by blood pressure control.


    store at 25c (77f); excursions permitted to 15- 30c (59- 86f) [see usp controlled room temperature].

    how supplied

    dibenzyline (phenoxybenzamine hydrochloride) capsules, 10 mg, in bottles of 100 (ndc 65197-001-01).

    this is one part of nursing school that i don't miss.
  5. by   phoenixfire
    Thank you thank you thank you! I was finally able to get ahold of my Pharm teacher earlier today, and she just said that it was a discontinued drug in the US, but I still wanted the information for it just in case I ever come across it for some reason.

    Just another reason I love being a member of this site..... :spin: