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Phenobarbital side effects--how long?

My dog (shepherd/husky mix, 73 pounds, 12 years old) began to have grand mal seizures last week. He had two seizures, one on Sunday and one on Monday, at almost exactly the same time in the evening. After the second seizure, the vet put him on phenobarbital (97 mg/2x per day).

He's been on it for five days now and is still pretty out of it. He is extremely lethargic (sleeps most of the day), has coordination problems, and weakness in his hind end. He walks veeery slowly. He's also extremely hungry and thirsty. I've read that all of these are possible phenobarbital side effects. How long do these usually last before the dog gets used to the medication? I'm hoping that these are not signs that something else is wrong, though I am aware of the possibilities.
397 Responses
974371 tn?1424653129
Oh, so sorry about the seizure problem. That can be frightening.  I personally don't know the answer to that question but, from what you are describing, it sounds like perhaps the dose might be too high.  You should contact your Vet with these questions and see if perhaps the dose needs to be adjusted.  Maybe the Vet wanted to start at this dose then try decreasing it later?
See if you can possibly find a group (maybe on Yahoo) that discusses dogs with seizures and see what others have experienced.
Good luck!!
Avatar universal
Obviously there's a load of detail I'm not including because of space issues.

We did contact the vet, who suggested we skip a dose and cut back to 64.8 mg 2x per day. We just did the first 64.8 mg dose. But the dog is still adjust to the meds, and the side effects and the question remain.

If anyone out there has had this issue and does know the answer, I'd appreciate your response. I'm just interested in any anecdotal evidence of how long to expect side effects to last.
1 Comments
My jake is 18 months old and started having seizures in March. He didn't have another until two months later. The vet put him on keppra and two weeks later he had a  seizure on Saturday and another on Sunday. The vet then put him on phenobarbital and increased his keppra to taking two twice a day. After taking these for about six days Jake started getting really clumsy an tripping , falling into walls, falling down the steps, etc an was extremely tired.
I was really worried so I called his vet. He advised me to cut back on his keppra to one pill twice a day plus phenobarbital twice a day. Within two days he stared acting more hisself .  I feel he was over medicated .
Avatar universal
In case anyone else has this problem, I want my experience to be available to them. There was very little to read on the DURATION of initial phenobarbital side effects on the web, and I was very frightened by what I saw. So, here's what happened with my dog.

The side effects (which were severe) lasted approximately three weeks. It is possible that they can last this long. Most people say they go away in a day or two, but in very sensitive dogs, it takes much longer. My dog was knocked flat by the loading dose and barely moved for the first couple of days. He bumped into objects, seemed blind, responded to sounds incorrectly (looked in the wrong direction), tripped, stumbled, and fell flat on his stomach a few times when trying to walk. He moved in slow motion and did not make a sound for a couple of weeks (not a single bark). He would also get confused, like when my other dog would nudge him, he'd bark at her, and continue barking at her even after she'd left the room. He also had extreme hind end weakness and started urinating in the house. These side effects abated so slowly it was agonizing, even after we cut back on his dosage. Every day, however, he has been slightly better. Finally, at three weeks, we're putting away the plastic sheeting, and watching him play again with our other dog. He's still not 100%--his reactions are slowed down, he sleeps more than usual, and he's very thirsty and hungry (he's started eating dirt from the potted plants--he is CRAZY hungry!), but he is SO much better.

So, this word of advice to anyone whose dog is on phenobarb, who is terrified by symptoms that mimic an aggressive brain tumor--don't panic. It might be a tumor (heck, my dog still might have a tumor), but it is also possible that it's the phenobarbital. Try to keep a log of what your dog does every day. Does he stop tripping one day? Does he manage to stand all through dinner one day? The progress is very slow. But if it's just drug side effects, it will get better.

Be understanding if your dog begins to soil the house. Get some baby gates and put him some place safe (we blocked our dog in the kitchen). Laminated fabric is also handy to have. And hang in there! It will pass, and you'll get your friend back within a month.
Avatar universal
My dog, a Boston Terrier, has just started having seizures and was placed on Phenobarbital 30 mg BID initiated ~ 4 weeks ago.  She too experienced similar symptoms (uncoordinated, urinating in the house, trouble walking or standing without swaying or falling, blindness (so it seemed), running into walls, not responding to my voice). It has now been 4 weeks on the medication. Most all has improved except:  instead of being fatigued and calm she has gone crazy mad!  She is extremely hyper, very jumpy when I try to pet her, barks non-stop (so much so that she becomes hoarse) and is up all hours of the night barking & wanting food or to go outside.  

I would like suggestions (if any) on what I can do to help calm her down, or stop the barking.  I have tried to hold her collar to hold her still and pet her slowly and gently which seems to help for a few minutes, but when I stop she goes crazy again.  HELP!  I need some rest and so does she.
Avatar universal
Thank you so much for your posting.  I am currently at that point (8 days) where I'm questionning how long this lasts.  My dog is larger -- Anatolian Shepherd mix, 9 years old -- and he is having one heck of a time with what I'm hoping is the Phenobarbital as well.  He has been in perfect health but just out of the blue had a grand mal seizure.  I took him to the veterinary hospital as it was in the evening and he had two more there.  Within 24 hours they got me in to see a neurologist and now he's being treated for a bad case of Valley Fever.

He drinks a ton and eats more, but my biggest concern is his lethargy and lack of coordination.  It takes him so much effort to get up, particularly the hind legs; it's so sad to watch.  So I'm hoping that, with time, this behavior changes.  I see some sites that say it will change in a few days to maybe two weeks and, if it was absolutely two weeks, I would be stressing out more and more as each day passed so .... Thanks for taking the time to post the outcome as it relates to your dog's behavior.  Regards.
Avatar universal
Hi I have a Staffy who is on Phenobarbital only been taking it 3 days.   I have read all the side effects online and he has all of them like your dog the medication appears to have made him hyper.  I am trying to take him walking for longer to try and get rid of some energy.  He appears to be sleeping more through the day then gets hyper in the evening also making lots of silly noises that he never made before.

He is also drinking more but I havent given him more to eat as yet any suggestions of how much more to give him to eat.  
Avatar universal
Hi I have a 3 year Boxer who started Phenobarbital in November. He is pretty much back to his old self. He still has a few seizures a month but the vet told me that might happen. He is not hyper but I would talk to your vet about this. As far as food, the vet told me to keep him on his normal diet cause if he overeats he will then become overweight. He was really hungry for about a month and a half but I think he is pretty much used to the medicine now. I wish you and your doggie all the best.
Avatar universal
I have a 10 year old cocker spanial.she got put on phenobabital 3 years ago.she was started on the lowest dosage32.1mg per day,and adjusted up to 96.3 per day.over 3 month period.she didn't show any of those side effects till now.blood work showed her levels were to high.my concern is are other vets starting y'all on too high of a dosage.because those side effects indicate too much is in their system.like I said it took 3 years for her to get those effects and it was because her high levels.her effects are no control of her rear legs.sleeps all the time,and no motivation.hope this helps someone.
Avatar universal
Try Bach's Rescue Remedy.  Regular human formula.  Put a few drops of the top of her head 10 minutes apart until she calms.  I have a beagle that has cluster seizures, is on phenobarb and potassium bromide and the Rescue Remedy does help her.  Good luck!
Avatar universal
My 15 yr old 17 lb poodle had cluster seizures 2 days ago. The vet gave him 2 doses of phenobarb and valium (the last dose at 1pm on March 13th). She thinks that he may have a brain tumor and said that if I did not continue with diagnosis, that I should put him down. I took him home and am letting the medication wear off to see if he has another seizure. Within 12 hours he went from completely sedate to eating drinking, walking and using the bathroom on his own. It has been 36 hours and I would say he is about 80% back to his regular self, but he is still showing side effects from the phenobarb (more than usual hunger, partial loss of coordination and hind end weakness and restlessness). Does anyone know how long it takes for phenobarb to get out of the system? The vet said approximately 12 hrs, but that is obviously not the case. Also, since this morning he is having unusual smelly penile discharge, but he is still urinating fine. Has anyone experienced this? Is this a something to worry about?

Also, I really do not like the effects of phenobarb and am talking to my vet about Zonasimide or possibly Felbamate. Does anyone have experience with these?
2 Comments
I have a pit bull mix that was put on phenobarbital yesterday my concern is she is not getting up to walk at all and sleeps alote she is eating and drinking normal and responds to us when we call her name she keeps her front legs straight and stiff and don't bend them that often her back legs seem weak and have to keep a pad under her to pee and poop anybody experience this??the doctor told me I have to allow healing time but she at least walked a little before going to vet
I have a pit bull mix that was put on phenobarbital yesterday my concern is she is not getting up to walk at all and sleeps alote she is eating and drinking normal and responds to us when we call her name she keeps her front legs straight and stiff and don't bend them that often her back legs seem weak and have to keep a pad under her to pee and poop anybody experience this??the doctor told me I have to allow healing time but she at least walked a little before going to vet
Avatar universal
My cocker is nine years old. About five years ago, I was told her skin problem was seborea.  She gets matting in her fur with a greasy foul smelling excretion. Under her neck, between her toes, and on her rear quarters. She got shaved one time and broke out all over with oozing sores. Then she got fatty tumors on her skin that cannot be "shaved".  Now she gets a longer cut to avoid arousing the sores.  A vet finally tested her thyroid and said she didn't make any, so he started her, raised the amount, and then she started having seizures.  A week ago, he doubled her amount to 32 mcg or whatever twice a day.  Last night she poo'd all over the house and back sidewalk.  I gave her phenobarb this morning, then she came to me with blood all over her mouth begging for her food.  I washed her up, fed her and now she is sleeping.  My husband said she wants food each time she takes her meds. I didn't realize this and waited a bit to feed her since she obviously had a stomach issue during the night. She hasn't had any seizures for a few weeks now, but I don't trust anyone who is treating her, now or in the past.  I feel like she needs a round of cefelexin and nothing else.  Her skin gets better when she took it before (yrs ago).  Does anyone know what I can do?  I am so sad watching this.  She has every side effect from the phenobarb...bad back legs, starting all day....  THANKS
Avatar universal
My sweet little pitty girl has been on it for a week. She also makes some goofy wobble like noises that I have never heard before.  She is soo stubborn too. She always was a little stubborn but listened perfectly to commands. Now she could care less about what we have to say. She eats my plants, the dirt, and chews everything. She flies through the air like a clumsy dolphin when excited.. which is really odd. She was having seizures multiple times daily which have stopped but why this behavior?? Will it go away??
675347 tn?1365460645
COMMUNITY LEADER
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Avatar universal
All i can say it that i hate the pheno side effects my dog has we are taking him off it all together and trying herb meds.My dog as not living a normal life and it is sad he is only 6 .All i can say is if your pet is on it please try some thing else if he is having bad side effects.Do you know that if your dog is having bad side effects and you take him off phen that them side effect can still be there the rest of his or her life IT IS NOT WORTH IT PLUS GIVES THEM LIVER DAMAGE .
Avatar universal
I just read your post. PLEASE email at ***@**** to fill me in on herb meds. I know nothing about them. My 6 yr old 10 lb terrier has seizures & they've started on phenabarbatol (however it's spelled) & after 4 days (& before reading all this) last week, I cut her back b/c she was so lathargic & out of it, upset stomach going to the bathroom everywhere, it was scaring me because she is normally very active.  I felt she was possibly over-medicated! But she had 2 seizures this am so I've put her back to the original dose the vet was starting her at. It's only been 1 1/2 weeks but I sure don't want her having lifetime effects!! :( Thanks for the info
Avatar universal
my border collie 11 has been on the same drug for 5 days, its awful hes thirsty and hungry all time, the house stinks, hes weeing himself, he can barely walk and has no strength in hind legs. his balance is terrible he can hardly stand. vet put him on lower dose but al he does is sleep. i too dont know how long this will last. its frustrating and upsetting i know.
Avatar universal
I too am having issues with the side effects of phenobarbital in my dog. We have an 11 yr old lab and he has had 3 seizures since March and the vet put him on this med. The side effects are terrible. I just finished cleaning up 4 huge piles of diarrhea on the carpet. He has little control over his hind legs, is extremely irritable, not acting as himself. He has only been on it for 3 days, and its 3 days too long. I plan on calling the vet this morning and taking him off.
Avatar universal
Hey ducky i would also like some info on the herb meds you tried...i know some plants are very effective but a little scared to try them...i feal next time my dog has a seizure he will die! he had a status epilepticus 3 days ago...convulsion for many hours...he was on potassium bromide before...i would by it and make the meds my self...worked for 3 years....with not much side effect...they just put him on pheno....there is something wrong with this drug! hate it...but so scared i keep giving it to him...i want my dog back...:( ***@****
Avatar universal
I'm so thrilled to have found this forum, and thread.  I have a 7yo female Boxer 75 lbs.  She's been having what I think were tiny seizures (foaming at the mouth) about 1x/week for a few weeks, vet wasn't very concerned.  Last Thursday 7/27 at 3pm she had her first major seizure ... scary.  She had another on Friday at 3AM and another at 2pm Friday.  I took her to 24hr hospital she had another while I was checking her in at 3pm Friday 7/27.  Blood work and chest xray are normal, no cancer noted all organs normal.  They wanted to do an MRI, but if there is a brain tumor I wouldn't put her through any surgery so I held off on that.  We started her with a loading dose of phenobarbital and I brought her home on 90mg x2 daily until she can see the neurologist tomorrow 7/30.  She is lethargic, yes, but has good appetite, is thirstry, but no accidents in the house.  Keeping her normal routine except for sleeping so much.  Have any of you gone the MRI route?  I'm hoping there is a more conservative approach, and a titration of the med to a dose that wont keep her zonked.  She has NOT had a seizure since Friday.  I'm grateful for that.  Any thoughts I'd appreciate it.
Avatar universal
It's been so long since I've been here. I got this in a private message and I thought I was posting... so here's my response. Maybe there are some nuggets in here that will help someone. The main takeaway is that my dog is doing well!

So, here you go:

Hello! The good news is that my guy is still around. We're continuing to tinker with his pheno levels--it is tricky business, because there is an impact to the liver, and that needs to be balanced with the benefits of the phenobarbital. Also, he's now on anipryl for dementia (he is 13), and that's adding some new stuff to the mix. He still has a grand mal about once every 37 days. We're continuing to try for better control, and we are gradually increasing the time between seizures. Here's a tip for others--pheno is generally given every 12 hours. My dog has a dose at 5 am and 5 pm (32.4 mg tablets @1.5 tablets each dose). We noticed, though, that whenever he had seizures, they tended to happen right around the 5 pm dose. So, we added a mini dose at noon. If he seems to have a lot of little twitchy focal seizures in the morning, we give him a whole tablet at noon. Otherwise, we give him a half tablet. This has worked really well! I can almost always predict when he will have a seizure (probably 80% accuracy) so I think we're heading off a lot of them with this strategy.

My dog never had diarrhea as a result of the pheno but different dogs react differently... You'll probably want to ask your vet about that. It can make your dog thirstier, so maybe that's affecting her GI system... You could try giving her a little pedialyte, which is just good in general for diarrhea. I'm not sure of the dosage for a toy poodle though--I would guess just 2 or 3 ml... But that's just a guess. I would google that before giving her any... We feed a high quality carb-free diet (Flint River Ranch Fish and Chips kibble mixed with Back To Basics organ meat kibble). I don't know if it helps dogs with seizures at all, but carb-free diets are recommended for children with epilepsy. I figure it can't hurt! We don't give him any rice, wheat, corn, etc., not even in his treats.

One more update for us that may help someone else--we also are giving him Denamarin (large dog, one tablet), four capsules of Milk Thistle, and four Liverite LiverAid tablets per day. These have dramatically improved his liver numbers. His vet was delighted with his last round of tests. His enzymes were starting to get into the danger zone--so high that we did an ultrasound looking for other reasons. Thankfully, they found nothing growing in his liver, so we did a lot of research and threw all those supplements at the problem, and it seems to be working. The phenobarbital is very hard on the liver, especially in an older dog whose liver enzyme numbers are likely to be high anyway. But we've actually brought his down to slightly higher than normal, which is GREAT for a dog his age. We buy the milk thistle capsules and LiverAid intended for people. I believe the quality is better. He was actually showing improvement before the Denamarin, so I'm not convinced that's helping as much as everything else. But hey, I'm not going to change anything now that he's heading in the right direction.
Avatar universal
Thank you so much for posting your questions and more importantly, following up with the progress of your dog!  I am so glad to hear he is doing so well a year later.  A few weeks ago, our elderly dog started with the head twitching, loosing feeling in his legs.  We talked to our vet and decided to keep an eye on him.  Last week he had a grand mal seizure and we were so frightened.  We prepared for the worst and it was suggested that he may improve with phenobarbital.  He's now been on the medication a few days now and his symptoms are identical to yours with the addition of he is making goofy noises at times.  It is a relief to know these are side effects of his medication and he'll improve.  This has been a really difficult thing for us (including our dog) to go through and it's comforting to see other pets have made it through. I really appreciate your taking the time to update with your dog's status because it's helped to ease my mind a lot.  
Avatar universal
my dog, 4 yrs old, had no history of seizures. got his vacines of distemper and rabies, that night started having seizures. 1 the 1st night and 6 the next night. took him to the vet. said it had nothing to do with the vacines. he was on phenobarbital 30mg (2 x's a day) for a month with no sezures. after 30 days he sarted having them again and now he is boosted up to 45mg. he is not the same dog. do i keep boosting his dose and have a zombie that wanders around aimless with the chace of liver damage or chance the seizures? i think 100% that he recieved to high of a dose of vacine and contracted some form of distemper. anyone else with simular exp?
Avatar universal
Hi, My 5 year old boxer started having seizures about 5 days ago. It started with focal seizures and we didn't know what they were so we took her to get emergency care where they told us what it was. She stayed overnight and had one of the big ones. She was diagnosed with either an inflammatory disease or an infection. We did both an MRI and a spinal tap. The doctor said he can't definitely rule out cancer, but he sounds pretty confident that it's not. She was put on phenobarb and is having the same symptoms. I think it's been about 3 or 4 days now. It's good to hear people who have seen their dogs get back to normal, but I'm also thinking of getting some natural remedies too. Does anyone know if natural supplements and phenobarb can work well together?

And also to PatD0719 I saw you asked about the MRI. I think it's a good idea to get it done just because you want to be sure of what it is, but it also costs a good amount of money so if you feel like your dog is doing ok maybe you could hold off. I did really like our doctor and he suggested getting it done so they have a better idea of what's causing it. It sounds like she's responding to the meds which is great! Good luck with everything! :)
Avatar universal
We have an 8 year old german shep cross,she had 2 fits and was put on phenobarb and they  cut her dose for exact same side affects as u
snowey 2 years on still has problems main 1 been weakness in her hind legs
shes not same dog anymore:)wish i could take her off them and get my energetic bouncing dog bck
her dose is quite low 1/60 morning half 60 pm
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