This copied post from my other forum is one from a member that is going to vet school so is a good read:
Mr. Vega
Senior Member
This is most likely what the OP found on VIN. This is directly out of Plumb's Veterinary Drug Handbook - a book that every veterinarian owns (so you don't really have to accept a negligence claim from your vet in the event that something bad happens due to this drug). If you're unsure of some of the mechanisms or whatever in the description, just ask and I'll explain them.
Phenylpropanolamine HCl
Prescriber Highlights
Sympathomimetic used primarily for urethral sphincter hypotonus
Caution: glaucoma, prostatic hypertrophy, hyperthyroidism, diabetes mellitus, cardiovascular disorders or hypertension
Adverse Effects: restlessness, irritability, hypertension, and anorexia
Drug Interactions
Chemistry
A sympathomimetic amine, phenylpropanolamine HCl occurs as a white, crystalline powder with a slightly aromatic odor, a melting range between 191°-194°C, and a pKa of 9.4. One gram is soluble in approximately 1.1 ml of water or 7 ml of alcohol.
Storage/Stability/Compatibility
Store phenylpropanolamine products at room temperature in light-resistant, tight containers.
Pharmacology
While the exact mechanisms of phenylpropanolamine's actions are undetermined, it is believed that it indirectly stimulates both alpha- and beta-adrenergic receptors by causing the release of norepinephrine. Prolonged use or excessive dosing frequency can deplete norepinephrine from its storage sites, and tachyphylaxis (decreased response) may ensue. Tachyphylaxis has not been documented in dogs or cats, however, when used for urethral sphincter hypotonus.
Pharmacologic effects of phenylpropanolamine include increased vasoconstriction, heart rate, coronary blood flow, blood pressure, mild CNS stimulation, and decreased nasal congestion and appetite. Phenylpropanolamine can also increase urethral sphincter tone and produce closure of the bladder neck; its principle veterinary indications are because of these effects.
Uses/Indications
Phenylpropanolamine is used chiefly for the treatment of urethral sphincter hypotonus and resulting incontinence in dogs and cats. It has also been used in an attempt to treat nasal congestion in small animals.
Pharmacokinetics
No information was located on the pharmacokinetics of this agent in veterinary species. In humans, phenylpropanolamine is readily absorbed after oral administration and has an onset of action (nasal decongestion) of about 15-30 minutes and duration of effect of approximately 3 hours (regular capsules or tablets).
Phenylpropanolamine is reportedly distributed into various tissues and fluids, including the CNS. It is unknown if it crosses the placenta or enters milk. The drug is partially metabolized to an active metabolite, but 80-90% is excreted unchanged in the urine within 24 hours of dosing. The serum half-life is approximately 3-4 hours.
Contraindications/Precautions
Phenylpropanolamine should be used with caution in patients with glaucoma, prostatic hypertrophy, hyperthyroidism, diabetes mellitus, cardiovascular disorders or hypertension.
Reproductive/Nursing Safety
Phenylpropanolamine may cause decreased ovum implantation; uncontrolled clinical experience, however, has not demonstrated any untoward effects during pregnancy.
Adverse Effects/Warnings
Most likely side effects include restlessness, irritability and hypertension. Anorexia may be a problem in some animals. Rare reports of "stroke" have occurred in dogs given therapeutic dosages of phenylpropanolamine.
Overdosage
Symptoms of overdosage may consist of an exacerbation of the adverse effects listed above or, if a very large over-dose, severe cardiovascular (hypertension to rebound hypotension, bradycardias to tachycardias, and cardiovascular collapse) or CNS effects (stimulation to coma) can be seen.
If the overdose was recent, empty the stomach using the usual precautions and administer charcoal and a cathartic. Treat symptoms supportively as they occur. Do not use propranolol to treat hypertension in bradycardic patients and do not use atropine to treat bradycardia. Hypertension may be managed with a phenothiazine (e.g. acepromazine--very low dose such as 0.02 mg/kg IV or IM). If phenothiazines do not normalize blood pressure, consider using a CRI of nitroprusside. Contact an animal poison center for further guidance.
Drug Interactions
Phenylpropanolamine should not be administered with other sympathomimetic agents (e.g., ephedrine) as increased toxicity may result.
Phenylpropanolamine should not be given within two weeks of a patient receiving monoamine oxidase inhibitors.
An increased chance of hypertension developing can result if phenylpropanolamine is given concomitantly with indomethacin (or other NSAIDs, including aspirin), reserpine, tricyclic antidepressants, or ganglionic blocking agents.
An increased risk of arrhythmias developing can occur if phenylpropanolamine is administered to patients who have received cyclopropane or a halogenated hydrocarbon anesthetic agent. Propranolol may be administered should these occur.
Doses
Dogs
For urethral sphincter hypotonus:
1. 12.5-50 mg PO q8h (Labato 1988), (Polzin and Osborne 1985), (Bartges 2003a)
2. Using the time-release 75 mg capsules: Dogs weighing less than 40 lbs: 1/2 capsule PO daily. Dogs 40-100 lbs: 1 capsule PO daily. Dogs weighing >100 lbs: 1.5 capsules PO per day. (Label information; Cystolamine® --VPL)
Cats
For urethral sphincter hypotonus:
1. 12.5 mg PO q8h (Labato 1988), (Polzin and Osborne 1985)
2. 1.5 mg/kg PO q8h (Bartges 2003a)
3. 1.1-2.2 mg/kg PO bid-tid (Lane 2003)
Monitoring Parameters
1) Clinical effectiveness; 2) Adverse effects (see above); 3) Blood pressure, if possible
Client Information
In order for this drug to be effective, it must be administered as directed by the veterinarian; missed doses will negate its effect. It may take several days for the full benefit of the drug to take place. Contact veterinarian if the animal demonstrates ongoing changes in behavior (restlessness, irritability) or if incontinence persists or increases.
Dosage Forms/Approval Status/Withholding Times
Veterinary-Labeled Products:
Phenylpropanolamine Chewable Tablets: 25 mg, 50 mg Proin® 50 (PRN Pharmacal), Propalin®(Evsco); (Rx). For use in dogs.
Phenylpropanolamine Timed-Release Capsules: 75 mg Cystolamine®(VPL); (Rx). For use in dogs.
Phenylpropanolamine oral solution: 25 mg/ml in 60 ml bottles, Proin Drops® (PRN Pharmacal) (Rx); 50 mg/ml in 30 ml and 100 ml bottles, Propalin® Syrup (Evsco); (Rx). For use in dogs.
Human-Approved Products:
Note: Because of potential adverse effects in humans, phenylpropanolamine has been removed from the US market for human use.
Phenylpropanolamine may also be known by the following synonyms: (+/-)-norephedrine, dl-norephedrine or PPA.
Mr. Vega
And this is another member's post that happened to be below Mr. Vega's---------
11-06-2009 #100
Rescue Momma
Hello all,
I'm so very sorry to hear of the sad stories of those of you who have lost your beloved family members. My heart goes out to you.
I found this site because I went online to research Prion. Thank god I did!
Thank all of you for your input and advice.
After reading this forum I had to post here and tell you of my experience with Prion so far. It has not been as traumatic as some of you have had but enough to make me see there is something wrong with giving my babies Proin.
I have been giving my youngest female Lil Bit Prion on and off for almost 2 weeks. She is about about 4 years old and is a Besenji/Boxer mix.
I called my vet the other day because I have been having trouble getting her to take them.
And when I do get it down her she is acting very lathargic and not herself. She NEVER lays still and everything is an adventure to her. He said that usually in his experience the dog may tend to be more excitable than normal but not lethargic. I was supposed to give her 2 tablets of 25mg a day about 12 hours apart.
I did not give her any for a few days to see if there was a difference and there was. I have been giving her one tablet a day and it doesn't seem to be as bad.
My vet said he could do the hormone therapy and has had good luck with it. Well after reading this she won't be doing that either. I'm going to the store tonight and get some soy milk and see what happens. Her incontinence has not been terrible and we will find a way to work around it rather than take a chance with her health.
This has been a real eye opener for me and again my condolences to those of you who have had pets lost.
As some of you stated that all of the losses may not have been Proin related but I for one am not taking any chances. Especially after her acting so different when I give it to her.
Thank you all again and god bless