Category: Neurology and Musculoskeletal Medications

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Probenecid Pharmacology

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Patients with G6PD deficiency who are taking probenecid are at increased risk for hemolytic anemia.

In a patient taking probenecid, they need to have adequate kidney function for the drug to work.

GI upset is likely the most common adverse effect of probenecid. It can be given with food.

Probenecid can raise the concentrations of many common antibiotics like penicillins and cephalosporins.

Remember that there are many medications that can oppose the beneficial effects of probenecid. Thiazides, niacin, and some immunosuppressants can raise uric acid.

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Morphine Pharmacology

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Morphine has opioid agonist activity that can cause respiratory depression and death in overdose.

Morphine-6-glucuronide is the metabolite that can accumulate and cause CNS toxicity in renal failure.

Be aware of CNS depressants that may enhance the effect of morphine and other opioids. Some examples of CNS depressants include gabapentin, benzodiazepines, older antihistamine, skeletal muscle relaxants, and pregabalin.

Opioid withdrawal is a significant concern when patients have their morphine or another opioid abruptly stopped. Some signs of withdrawal include agitation, mood swings, anxiety, sweating, GI upset, pain, and insomnia.

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Naloxone Pharmacology

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Naloxone is a life saving drug that can help manage an opioid overdose situation.

Naloxone blocks opioids receptors so opioid agonists cannot bind there.

One of the biggest risks with opioid overdose includes respiratory depression. Naloxone can help reduce the risk of this if administered in a timely manner.

IV naloxone will have the quickest physiological onset of action, but nasal naloxone may be the best opportunity in the community to get this drug on board quickly.

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Benzodiazepine Pharmacology

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Benzodiazepines act by enhancing the effect of GABA, an inhibitory neurotransmitter.

Benzodiazepines can cause confusion, sedation, and respiratory depression.

There are many potential indications for benzodiazepines. They can be used in anxiety, status epilepticus, insomnia, and alcohol withdrawal amongst other things.

There is a boxed warning for the use of opioids with benzodiazepines. The primary risk of the combination is respiratory depression.

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Celecoxib Pharmacology

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Celecoxib is easy to remember as its mechanism of action is “COX”-2 Inhibition. This can result in result in reduced prostaglandin formation and help with pain and inflammation.

Kidney function is important to monitor in our patient on celecoxib. It is especially important in patients taking ACE inhibitors, ARBs, and/or diuretics.

While GI bleed may be less likely with celecoxib compared to traditional NSAIDs like indomethacin and ibuprofen, it still needs to be monitored for.

Digoxin concentrations may be increased with the use of celecoxib.

Celecoxib is generally dosed twice per day as the half-life of the drug is in the ballpark of 10-12 hours.

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Benztropine Pharmacology

Benztropine Pharmacology

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Benztropine is a highly anticholinergic medication that is primarily used for movement disorders.

Antipsychotics can cause extrapyramidal adverse effects that can help be managed with benztropine.

Because benztropine is highly anticholinergic, it can cause dry eyes, dry mouth, urinary retention, constipation and contribute to falls and confusion, particularly in our elderly population.

While benztropine is classified as an anti-Parkinson’s agent, it is rarely used for that indication as it has a high incidence of anticholinergic adverse effects (particularly at the doses that are required for benefit).

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Sulfasalazine Pharmacology

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Sulfasalazine is a medication that can be used for diseases like rheumatoid arthritis, Crohn’s disease, and Ulcerative Colitis.

Because sulfasalazine can cause GI upset, this is a major reason why we try to break up the dose and give it multiple (at least two) times per day.

LFT and CBC monitoring are recommended with sulfasalazine due to its low potential to cause liver dysfunction, aplastic anemia, and agranulocytosis.

Sulfasalazine can impair folic acid absorption and lead to potential deficiency. A patient deficient in folic acid is at higher risk for developing anemia.

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Carbamazepine Pharmacology

Carbamazapine Pharmacology

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On this episode, I discuss carbamazepine pharmacology. This drug is most commonly used for seizures, bipolar disorder, or trigeminal neuralgia.

Carbamazepine is an autoinducer and can reduce the concentrations of numerous drugs. Some examples include apixaban, warfarin, rivaroxaban, diltiazem, verapamil, and many more!

Carbamazepine has the potential to cause Steven Johnson’s Syndrome. This has a much greater chance of happening in patients with certain genetics.

Carbamazepine can contribute to SIADH and cause significant hyponatremia.

Carbamazepine has boxed warning for numerous potential events like aplastic anemia, agranulocytosis, and the above-mentioned SJS.

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Valproate Pharmacology

Valproate Pharmacology

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Valproate (valproic acid, Depakote) has numerous uses which includes migraines, seizures, and bipolar disorder.

In a patient who is taking valproate, it is important to monitor for signs and symptoms of confusion as this drug can cause elevated ammonia levels.

When switching between dosage forms of valproate, you must recognize that the bioavailability is not the same between each different dosage form. This could lead to toxicity or treatment failure.

Valproic acid has a boxed warning for hepatotoxicity and liver function needs to be monitored.

Valproic acid can increase lamotrigine levels which ultimately could lead to an increased risk of lamotrigine induced SJS.

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Donepezil Pharmacology

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On this episode I discuss the pharmacology of donepezil.

Donepezil is an acetylcholinesterase inhibitor. In dementia, that is a deficiency in acetylcholine and donepezil helps preserve this neurotransmitter.

Donepezil can cause weight loss, GI upset, and diarrhea. This is an important monitoring parameter in our dementia patients.

There is the possibility for donepezil to cause bradycardia and insomnia. Keep an eye out for these adverse effects as they can and do happen in real practice.

Anticholinergics are notorious for blunting the effects of donepezil. We must look out for drug interactions from older anticholinergics like diphenhydramine, amitriptyline, and hydroxyzine.

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