Thursday, May 23, 2013

A History of Gonococcal Resistance: Are We Screwed?

Gonococcal infection is a growing public health problem that continues to remain of concern in the United States. Infection can occur in a number of anatomical sites, including the urethra, rectum, oropharynx, eye, and endocervical canal. Complications of untreated infection may lead to damage of reproductive organs, which may include pelvic inflammatory disease, infertility, and ectopic pregnancy in females, as well as disseminated gonococcal infection and conjunctivitis in neonates. With all of these potential complications, it is especially important to be able to recognize signs and symptoms of infection and treat patients with empiric antimicrobial therapy if there is a high index of suspicion.

A few weeks ago, I saw this tweet in my Twitter feed, which prompted my attention and piqued my interest:


The evolution of antimicrobial agents that have been used to treat this infection over the past century is quite fascinating, but somewhat disheartening at the same time. With the discovery of penicillin and sulfonamide in the early part of the 20th century, these two agents were hailed as the "go-to" treatments of this infection. Fast forward a few decades and after discoveries were made regarding the growing resistance patterns of gonococcal strains to these agents as well as tetracyclines, adjustments to treatment strategies for this infection had to be made relatively quickly. This also prompted the implementation of the Gonococcal Isolate Surveillance System (GISP) in the mid 1980s, which was designed by the Centers for Disease Control and Prevention (CDC) as a surveillance tool of susceptibility patterns of gonorrhea among cultures obtained from infected men at participating clinics. This would allow for recognition of early resistance to allow for prompt recommendations to be made for alternative therapies.

Fluoroquinolones and spectinomycin then came on the scene and were used along with both oral and parenteral cephalosporins (namely cefixime and ceftriaxone, respectively) in the 1990s and 2000s. However, in the early 2000s, a number of strains emerged in California and Hawaii that demonstrated increasing resistance to fluoroquinolones, particularly among infected homosexual males, and these strains eventually made their way into the heterosexual population. This led to modification of the treatment recommendations for gonococcal infection by the CDC in 2007 to remove fluoroquinolone therapy as a treatment option for this disease state. At this point in time, spectinomycin had already been removed from the United States market for a year as well. This further limited our treatment options to cephalosporins and...cephalosporins (oral and parenteral).

Even the last two years have been huge for the cephalosporins used to treat gonorrhea. In 2011, the CDC recommended higher doses of ceftriaxone to be used for gonococcal infection (250 mg from 125 mg) due to treatment failures, decreased in vitro susceptibility, and greater demonstrated efficacy for pharyngeal infection. The CDC has also recently recognized the growing number of isolates of gonorrhea that exhibited elevated minimum inhibitory concentrations (MICs) to cefixime, which increased by 17-fold from 2006 through 2011. This had already been a problem across the EU and Asia, and eventually made its way to the United States, particularly among men in the western part of the United States and the homosexual population. With the fear that this may contribute to resistance, the CDC made a statement this past August of no longer recommending cefixime or other oral cephalosporins as first-line therapy for the treatment of gonorrhea.

So where does this leave us? It is difficult to predict how successful the 10 by '20 campaign for the discovery and development of new antimicrobial agents will be. There is one ongoing trial that is evaluating a new treatment option (solithromycin [CEM-101], a macrolide antibiotic) for uncomplicated gonococcal infection. There is another trial that is currently evaluating the efficacy of azithromycin as a combination with either gemifloxacin or gentamicin for the treatment of gonorrhea. However, until these trials are completed, our best option for now is to increase public awareness of this situation and ensure that patients and their partners are adequately and effectively treated in order to minimize complications secondary to infection as a means of decreasing disease burden and health care costs. In addition, the CDC has developed a response plan for public health awareness of cephalosporin-resistant strains of gonorrhea.

The importance of reporting of patterns of resistance to the appropriate channels for epidemiological purposes and public awareness cannot be emphasized further. The history of gonococcal resistance should serve as a lesson to all of us on how quickly antimicrobial resistance can evolve and develop and highlight the therapeutic challenges that we may potentially be faced with as this continues to inevitably occur with other infectious diseases.

References:
MMWR Recomm Rep 2010; 59(RR-12):1-110.
MMWR Morb Mortal Wkly Rep 2007; 56:332-336.
MMWR Morb Mortal Wkly Rep 2011; 60:873-877.
MMWR Morb Mortal Wkly Rep 2012; 61:590-594.
MMWR Morb Mortal Wkly Rep 2013; 62:103-106.

Monday, May 20, 2013

Protamine Sulfate for LMWH


There is much discussion lately regarding new reversal strategies of oral anticoagulants that are rapidly growing in popularity.  While the data to support the use of agents like PCC and aPCCs are limited, our clinical experience is also lacking.  So-called ‘old school’ reversal agents, though infrequently used, still have a place for patients who receive parenteral anticoagulation. 

Protamine sulfate, our favorite salmon sperm derived drug, was (and still is) our go to reversal drug for heparin products.  The clinical experience with protamine for reversing heparin in cardiac surgery patients is extensive.  The effectiveness of protamine for reversing the effects of low molecular weight heparins is regarded as incomplete.  Since the mechanism of protamine relies on its positive charge and the large molecular weight of unfractionated heparin and its net negative charge, LMWHs by definition provide a smaller target that is less strongly attracted to protamine. While it is suggested to utilize protamine for LMWH reversal, other strategies such as PCC may be a consideration since the effects of protamine may be short lived due to its 7 minute half-life. [Am. J. Hematol, 2012; 87:S119–S126, CHEST, 2012;141(Supp.2): e24S-e43S]

The dosing of protamine for LMWHs is significantly less complicated than UFH.  Dosing recommendations are 1 mg of protamine for every 100 anti-Xa units of LMWH (Enoxaparin 1mg = 100 anti-Xa units) administered over the previous 8 hours with a maximum protamine dose of 50 mg. If it has been greater than 8 hours since the last LMWH dose, the dose of protamine decreases to 0.5 mg for every 100 anti-Xa units of LMWH. [CHEST, 2012;141(Supp.2): e24S-e43S]

Dosing of protamine is quite critical since protamine itself can paradoxically illicit anticoagulant effects through reduction in the rate of Factor V activation.  The problems with protamine do not stop there. Rapid administration can cause profound hypotension and bradycardia, pulmonary vasoconstriction, transient neutropenia, and although highly the highly warned risk to patients who’ve previously received NPH insulin (the “p” is for protamine, neutral protamine Hagedorn) developing anaphylactic reactions, the risk is about 1%.
Importantly protamine will not work with fondaparinux or any other anticoagulant (parenteral or oral) that is not technically a heparin. [Journal of Pharmacy Practice
23(3) 217-225]

Thursday, May 16, 2013

Pyridoxine (B6) for Refractory Status Epilepticus: "Fly Like A G6"

The case: TR is a one-year-old infant who presents to your emergency department with a tonic-clonic seizure. According to the paramedics, the seizure has lasted for approximately 10 minutes. She has no known past medical history. Vital signs are relatively stable, and a bedside blood glucose is performed, revealing a level of 105 mg/dL. She has a weight of 10 kg. IV access is established and 1 mg of lorazepam IV push is administered. The seizure stops within five minutes of administration of lorazepam, and this is followed by a post-ictal period that lasts for 20 minutes. After 20 minutes, TR seizes again, and a second dose of lorazepam 1 mg IV is administered. Despite this, TR still continues to seize for a period of 10 minutes, and the decision is made to administer a loading dose of fosphenytoin 200 mg IV. Despite this, TR still continues to seize. The pediatric ED attending physician turns to you and states:

"I am not crazy about the idea of intubating the patient and inducing a coma. Do you think pyridoxine is worth a try?"

First, let me start off with some definitions. Status epilepticus is characterized as either continuous seizures that last for more than five minutes, or two or more seizures without full recovery of consciousness between seizures. Refractory status epilepticus (RSE) is defined as the persistence of SE despite treatment with benzodiazpines and an antiepileptic drug (AED) (1, 2).

In terms of the treatment algorithm for SE, we generally start off with a benzodiazepine, followed by an AED if the seizure continues to persist, of which there are a number of agents to choose from: phenytoin, fosphenytoin, levetiracetam, valproic acid, phenobarbital, and lacosamide. If the seizure continues to persist despite treatment, a coma is induced in the patient using a sedative such as midazolam, pentobarbital, or phenobarbital (1).

Pyridoxine (vitamin B6) is a water-soluble vitamin that plays a role in a number of physiological enzymatic processes in the human body. Its biologically active form is pyridoxal-5'-phosphate (P5P). The following diagram illustrates the role of pyridoxine in the production of gamma aminobutyric acid (GABA):


In essence, low concentrations of pyridoxine and/or dysfunction in glutamic acid decarboxylase can lead to deficient concentrations of GABA, which can induce seizure activity. There are a number of current established uses of pyridoxine, which include the management of intoxications secondary to isoniazid, monomethylhydrazine (e.g. Gyromitra mushroom), and ethylene glycol ingestion (3, 4). 

It also has a role in pyridoxine-dependent seizures (PDS). This disorder was first described in 1954, and it is a rare autosomal recessive disorder that typically occurs within the first few weeks of the life of the neonate. It occurs secondary to mutations in the ALDH7A1 (antiquitin) gene, which leads to accumulations in the enzyme known as D1-piperideine-6-carboxylase. This enzyme inactivates P5P, which would ultimately prevent production of GABA. Patients can present with a wide array of symptoms, but the most common presentation is status epilepticus that is refractory to AEDs (5, 6, 7, 8).

Several case reports do highlight the utility of pyridoxine in patients presenting with SE refractory to AEDs. In addition, pyridoxine may also play a role in older patients who present with SE after discontinuation of maintenance treatment with oral pyridoxine in those patients who have an established diagnosis of PDS (6, 9, 10, 11). However, there are some challenges that may be encountered by clinicians in the emergency department in recognizing SE secondary to PDS. There is really no way of determining and recognizing that the patient does have PDS if it is the patient's first episode of SE. In addition, our primary concern is to stabilize patients in SE in order to prevent progression to irreversible morbidity and/or mortality. 

Times really have not changed when it comes to recommendations regarding pyridoxine for RSE. Authors of an editorial published in 1998 suggested that pyridoxine should be administered to patients experiencing seizures who are refractory to intravenous benzodiazepines. In addition, the most recent guidelines for SE recommend the use of pyridoxine in young children who experience SE in case PDS is the cause of SE (1).

In terms of dosing recommendations of IV pyridoxine for RSE, keep in mind that the dose is not weight-based, even in our pediatric patient. It is recommended that patients receive a loading dose of 100 mg IV, which may be repeated every 10 minutes up to five doses or until there is manifestation of response. From our own experience, pyridoxine works within minutes of administration; cessation of convulsions occurs almost instantaneously, and if seizure activity is being monitored through an electroencephalogram, normalization of the pattern can be observed immediately (12, 13).

It is recommended that all hospitals should keep 10 g of IV pyridoxine in stock for emergency administration (14, 15). Since the 1-mL vial containing 100 mg/mL is commercially available, this is equivalent to 100 vials. This is important, especially when if one suspects that SE is secondary to a toxic ingestion such as isoniazid, where the maximum dose that is recommended for this ingestion is 5 g. However, a number of studies have been conducted that have shown us the reality of stock in most hospitals. One study was a survey that was conducted of over 200 general and pediatric hospitals. It was found that IV pyridoxine was not on formulary in 9% of all general hospitals surveyed. In addition, only 20% of both general and pediatric hospitals had IV pyridoxine available in the emergency department. A second study showed that inadequate initial doses of IV pyridoxine was administered in 85% of patients evaluated, which can potentially lead to delayed improvement in clinical outcomes if waiting for additional stock to arrive from local area hospitals. It is especially convenient that IV pyridoxine is relatively inexpensive (only $2.50 per 100 mg/mL vial).

Anecdotally, we have administered IV pyridoxine at a dose of 100 mg to select patients with RSE with positive results. It can be considered a reasonable option for the management of RSE in patients without a clear etiology when traditional therapies are ineffective. Sufficient stock should be ensured to administer an adequate initial dose to patients in whom a toxicologic etiology of RSE is highly suspected.

Pop culture does recommend to be "fly like a G6", which I wholeheartedly agree with.

 

However, to make it relevant to the management of RSE, my recommendation is to "try out the B6."
 

References: 
1. Brophy GM, Bell R, Claassen J, et al. Neurocrit Care 2012; 17:3-23. 
2. Bleck TP. Curr Opin Crit Care 2005; 11:117-120. 
3. Lheureux P, Penaloza A, Gris M. Eur J Emerg Med 2005; 12:78-85. 
4. Minns AB, Ghafouri N, Clark RF. Pediatr Emerg Care 2010; 26:380-381.
5. Gospe SM. Pediatr Neurol 2002; 26:181-185.
6. Russell KE, Mulligan SR, Mallory LA. Pediatr Neurol 2012; 47:141-143.
7. Gospe SM. Curr Opin Neurol 2006; 19:148-153. 
8. Basura GJ, Hagland SP, Wiltse AM, et al. Eur J Pediatr 2009; 168:697-704.
9. Yoshii A, Takeoka M, Kelly PJ, et al. J Child Neruol 2005; 20:696-698.
10. Goutieres F, Aicardi J. Ann Neurol 1985; 17:117-120. 
11. Yoshikawa H, Abe T, Oda Y. J Child Neurol 1999;14:687-690.
12. Abend NS, Dlugos DJ. Pediatr Neurol 2008; 38: 377-390. 
13. Shorvon S, Ferlisi M. Brain 2012; 135:2314-2328.
14. Dart RC, Goldfrank LR, Chyka PA, et al. Ann Emerg Med 2000; 36:126-132.
15. Marraffa JM, Cohen V, Howland MA. Am J Health Syst Pharm 2012; 69:199-212.

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