Commonly Used Drugs in Neurology

Clorazepate
• Drug Class: Benzodiazepine, DEA schedule IV
• Purpose: This medication is used as a “rescue” drug to help control cluster seizures - it is not used as a daily maintenance drug
• Side effects: Can cause sedation and in some cases (uncommon), hyperactivity
• Dosing: Starting dose is about 0.5 mg/kg but it may be doubled or tripled if seizures are persistent
• This drug is typically given for 6 doses (sometimes 9 doses) every 8 hours to stop a cluster event

Gabapentin
• Drug Class: Neuropathic Pain Analgesic, Anxiolytic
• Purpose: Primarily given for pain management
• Sometimes used to reduce anxiety prior to a stressful event
• Side effects: Can cause mild sedation, ataxia (i.e., “wobbly” gait) and occasionally diarrhea
•Dosing: This medication is given every 8 hours. It is not important that the spacing of the doses is a perfect 8 hours, and practically speaking, we advise that it be given first thing in the morning, in the midafternoon (or as soon as you get home from work), and right before bed.

Leflunomide
• Drug class: Immunomodulator
• Purpose: This medication is used to “tamp down” the immune system in the treatment of immune-mediated diseases
• Side effects: Generally well tolerated, but occasional adverse effects in dogs include diarrhea, decreased appetite, lethargy, vomiting; these side effects tend to occur when higher doses are used.
• Vomiting and lethargy have been reported in cats.
• Dosing: Once per day (every 24 hours)

Levetiracetam (Trade name: Keppra®)
• Drug class: Anticonvulsant
• Purpose: Used as a daily anti-seizure medication in dogs and cats.
• Occasionally used as a short-term “rescue medication” to control cluster seizures
• Side effects: Levetiracetam is generally well tolerated in dogs and cats. The most common side effects reported include sedation and ataxia in dogs and reduced appetite, ataxia, hypersalivation, and lethargy in cats. These effects are usually mild and transient.
• Dosing: Available in two formulations: Regular Keppra (three times per day dosing) and Extended-Release (XR)(2 times per day dosing) formulations
• Cannot split the XR formulation

Neostigmine
• Drug class: Parasympathomimetic (Cholinergic)
• Purpose: Used to aid in the diagnosis of myasthenia gravis. Can be used to treat myasthenia gravis in patients for whom oral medications are not possible (i.e., it is given as an injection in a hospital setting)
• Side effects: Overdoses of neostigmine can cause nausea, vomiting, diarrhea, excessive salivation and drooling, tearing, changes in heart rate, cardiac arrhythmias, low blood pressure, muscle cramps, extreme weakness, agitation, restlessness, or paralysis.
• Imepitoin (Trade name: Pexion®)
• This drug is licensed in the United Kingdom and European Union as an anticonvulsant for idiopathic epilepsy in dogs. It is generally well tolerated and effective. It is similar in efficacy to phenobarbital, but may have few side effects. It was recently approved in the United States for the treatment of noise aversion in dogs, but practically speaking is still not available in this country. More to come if we can ever get our hands on this drug.

Phenobarbital
• Drug class: Barbiturate anticonvulsant, DEA schedule IV
• Purpose: Anti-seizure medication • Side effects: Can cause sedation, agitation, increased hunger/thirst/urination, weight gain and elevated liver enzymes
• Will artifactually lower thyroid in dogs
• In rare cases, liver toxicity can occur
• Dosing: Every 12 hours
• Monitoring: Phenobarbital blood levels (as well as a biochemical profile and complete blood count) are required 2-3 weeks after the drug is started, 3 months after starting, and then every 6-9 months thereafter. Pheno blood levels also need to be checked 2-3 weeks after any dosing changes.
• Phenobarbital loading: Because it can take weeks before orally administered phenobarbital achieves steady state in the blood, some patients benefit from a “pheno load” at the start of therapy. When this is done, the drug becomes theraputic right away. During a “load”, the patient is in the hospital and a catheter is placed. A large dose of the drug is given as an injection of the course of 3-12 hours.

Potassium Bromide (KBr) (Trade name: KBroVet®)
• Drug class: Anticonvulsant
• Purpose: Daily Anti-seizure medication
• Side effects: The most common side effects are ataxia (“wobbly gait”), followed by sedation, increased thirst, increased urination, increased hunger and resultant weight gain, vomiting, and mild elevations in certain liver enzymes. Less commonly, constipation, diarrhea or decreased appetite may occur.
• Less commonly, pancreatitis may occur.
• The side-effects of ataxia and sedation are common and typically transient (lasting up to 3 weeks); conversely, some dogs show signs of irritability and restlessness.
• Bromide use has been shown to reduce trainability in epileptic dogs.
• GI side effects, particularly during oral loading doses, may be reduced or avoided by giving with food or dividing the dose.
• This drug is not used in cats due to the potential for adverse effects, in particular, severe allergic lung disease
• Dosing: Every 12-24 hours
• This drug has a very long half life, meaning it takes months to achieve a therapeutic blood level. This necessitates what we call a KBr “load” to achieve therapeutic bromide concentrations faster - Approximately 700 mg/kg is given over 6-10 doses before dropping down to the patient’s once or twice per day maintenance dose
• Do not feed salty snacks or make abrupt dietary changes; keep chloride in diet stable.

Pyridostigmine (Mestinon) (Trade name: Mestinon®)
• Drug Class: Drug class: Anticholinesterase Agent
• Purpose: Used for treatment of myasthenia gravis
• Dosing: 0.2 – 2 mg/kg PO every 8 to 12 hours
• Side-effects: Adverse effects are usually dose-related symptoms, including GI effects (nausea, vomiting, diarrhea, salivation), respiratory effects (increased bronchial secretions, bronchospasm, pulmonary edema, respiratory paralysis), ophthalmic effects (miosis, blurred vision, lacrimation), cardiovascular effects (bradycardia or tachycardia, cardiospasm, hypotension, cardiac arrest), muscle cramps, sweating, and weakness
• The onset of action after oral dosing is generally within 1 hour

Tamsulosin (Trade name: Flomax®)
• Drug Class: Alpha-1 Adrenergic Antagonist
• Purpose: Ureteral/urethral relaxant (i.e., relaxes the muscles that line the urethra to allow the patient to pass urine more easily)
• Dosing: Every 12-24 hours
• Topiramate
• Anticonvulsant
• Can cause sedation, ataxia, inappetence, vomiting and weight loss • Available in 25mg, 50mg and 100mg tablets • Dosing can be every 8 or 12 hours • Zonisamide • Anticonvulsant
• Can cause sedation, ataxia, inappetence and vomiting
• Available in 25mg, 50mg and 100mg capsules
• Dosing can be every 24 hours in cats, q 12 hours in dogs