Drug Interaction:
Ephinephrine and ephidrine Vasoconstricting and hypertensive efects of these drugs are antagonized by phenilamine
Indication:
Pheochromocytoma
Agents for Pheochromocytoma includes- Phenotolame, Phenoxybenzene HCL, Metryrosine ,
Adverse Reaction:
Acute and prolonged hypotensive episodes, tachycardia, and cardiac arrhythmias Weakness, diziness, flushing, orthostatic hypotension, nasal stuffiness, nausea, vomiting, diarrhea
Contra-Indications:
Myocardial infarction, coronary insifficiency, angina or other evidence suggestive of coronary artery disease, Hypersensitivity to phenolamine or related compounds
Special Precautions:
Myocardial infraction, cerbrovascular spasms and cerbrovascular occulsion have followed
phentolamine, usually in association with marked hypotensive episodes with shock-like states which occassiuonally follow parentral use.
For screening tests in patients with hypotension, the generally available urinary assay of
catecholamine or other biochemical asays have largely supplanted phentolamine and other
pharmacological tests.
None of the chemical or pharmacological tests are infallable in the diagnosis of pheochromocytoma.
Phentolamine test is not the procedure of choice, reserve for cases in which additional conformity evidence is necessary and consider risks involved
Tachycardia and cardiac arrhythmias may occur with phentolamine use. When posible differ use of cardiac glycosides until cardiac rhytm returns to normal.
Pregnancy and lactation:
Safey for use during pregnancy or lactation has not been established. Use when clearly needed.
Dosages/ Overdosage Etc:
Indications:
Pheochromocytoma
Dosage:
Prevention of hypertensive episodes
Inject 5mg IV or Im 1 or 2 hours before sugery
Overdosage-
Symptoms/Treatment
1. If blood pressure to a dangerous level or other evidence ofshock occurs, treat vigourously and promptly .
2. Include IV infusion of norepinephrine, titrated to maintain normal blood pressure
3. Epinephrine is contraindicated because it stimulates both alpha and bata receptors, since alpha receptors are blocked.
The net result of eepinephrine administration is vasodilation and a further drop in blood pressure (epinephrine reversal)
Missed dose-
1. If you miss a dose of this medicine, take it as soon as possible.
2. However, if it is almost time for next dose, skip the missed dose and go back to your regular dosing schedule.
3. Do not double doses.
Patient Information:
1. Allergy-
Tell your doctor if you have ever had any allergic reactin to phenotolamine or food substances , presrvatives, dyestuffs etc
2. Older adults-
No studied in older people. Not known whether they work exactly in the same way as they do in younger adults. It is not expected to cause any different side effcts or problems in older people than it does in younger adults.
3. Other medicines-
Tell your doctor if you are taking other prescriprion medicines or OTC medicines.
4. Other medical problems-
Tell your doctor if you have other medical problems especially-
Bleeding problems- these conditions increase the risk of bleeding at the place of injection
5. Dosing-
Follow doctors instructions
6. Missed dose-
If you miss a dose of this medicine take it as soon as possible. However if it is almost time for your next dose go back to your regular dosing schedule.
Do not double doses.
7. Storage-
Keep the medicines out of reach of children
Store the medicines away heat and direct light
Do not store tablets or capsules in the bath room, in damp places near the kitchen sink
Heat and dampness will cause the medicines to break down
Keep the medicine from freezing
.
Pharmacology/ Pharmacokinetics:
Pharmacology:
Phentolamine, an alpha adrenergic blocking agent, blocks presynaptic (alpha 2 ) and postsynaptic ( alpha1) adrenergic receptors. It is a competitive antagonist of endogenous and exogenous alpha- active agents. It also acts on both the arterial tree and the venous bed. Thus, total peripheral resistence is lowered and venous return to the heart is diminished. Phentolamine also causes cardiac stimulation Phentolamine has an immediate onset and short durastion of action.
Interaction with Food:
Not reported.
Pregnancy and lactation:
Pregnancy and lactation:
Safey for use during pregnancy or lactation has not been established. Use when clearly needed.
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