Pharma Tips

Botulinum Toxin

By: Pharma Tips | Views: 9921 | Date: 29-Jun-2010

Botulinum toxin (abbreviated either as BTX or BoNT) is produced by Clostridium botulinum, a gram-positive anaerobic bacterium. The clinical syndrome of botulism can occur following ingestion of contaminated food, from colonization of the infant gastrointestinal tract, or from a wound infection.

Botulinum Toxin

1. INTRODUCTION
Botulinum toxin (abbreviated either as BTX or BoNT) is produced by Clostridium botulinum, a gram-positive anaerobic bacterium. The clinical syndrome of botulism can occur following ingestion of contaminated food, from colonization of the infant gastrointestinal tract, or from a wound infection.
BoNT is broken into 7 neurotoxins (labeled as types A, B, C [C1, C2], D, E, F, and G), which are antigenically and serologically distinct but structurally similar. Human botulism is caused mainly by types A, B, E, and (rarely) F. Types C and D cause toxicity only in animals.
The BoNT molecule is synthesized as a single chain (150 kD) and then cleaved to form the dichain molecule with a disulfide bridge. The light chain (~50 kD - amino acids 1-448) acts as a zinc (Zn2+) endopeptidase similar to tetanus toxin with proteolytic activity located at the N-terminal end. The heavy chain (~100 kD - amino acids 449-1280) provides cholinergic specificity and is responsible for binding the toxin to presynaptic receptors; it also promotes light-chain translocation across the endosomal membrane.





1.1. HISTORY
The German physician and poet Justinus Kerner (1786-1862) first developed the idea of a possible therapeutic use of botulinum toxin, which he called "sausage poison."
In 1870, Muller (another German physician) coined the name botulism. The Latin form is botulus, which means sausage.
In 1895, Professor Emile Van Ermengem, of Belgium, first isolated the bacterium Clostridium botulinum.
 In 1928, Dr. Herman Sommer, at the University of California, San Francisco, first isolated in purified form botulinum toxin type A (BoNT-A) as a stable acid precipitate.
In 1946, Dr. Edward J Schantz succeeded in purifying BoNT-A in crystalline form–cultured Clostridium botulinum and isolated the toxin.
 In 1949, Dr. Burgen's ASV group discovered that botulinum toxin blocks neuromuscular transmission.
 In the 1950s, Dr. Vernon Brooks discovered that when BoNT-A is injected into a hyperactive muscle, it blocks the release of acetylcholine from motor nerve endings.
 In 1973, Dr. Alan B. Scott, of Smith-Kettlewell Eye Research Institute, used BoNT-A in monkey experiments; in 1980, he used BoNT-A for the first time in humans to treat strabismus.
 In December 1989, BoNT-A (BOTOX®) was approved by the US Food and Drug Administration (FDA) for the treatment of strabismus, blepharospasm, and hemifacial spasm in patients aged younger than 12 years.
 On December 21, 2000, BoNT-A received FDA approval for treatment of cervical dystonia.
 In 2001, the United Kingdom approved BOTOX®, synthesized by Allergan, for axillary hyperhidrosis (excessive sweating). Canada approved BOTOX® for axillary hyperhidrosis, focal muscle spasticity, and cosmetic treatment of wrinkles at the brow line.
 On April 15, 2002, the FDA announced the approval of BOTOX® Cosmetic to temporarily improve the appearance of moderate-to-severe frown lines between the eyebrows (glabellar lines).
 In July 2004, the FDA approved BOTOX® to treat severe underarm sweating, known as primary axillary hyperhidrosis, that cannot be managed by topical agents, such as prescription antiperspirants.
 Although it has not been approved by the FDA for any other indications, the acceptance of BoNT-A use for the treatment of spasticity and muscle pain disorders is growing, with approvals pending in many European countries.
 The clinical use of BoNT-B has been studied, and several products currently are available commercially (eg, MyoBloc, in the United States; NeuroBloc, in Europe). MyoBloc was approved by the FDA on December 8, 2000, for treatment of cervical dystonia, to reduce the severity of abnormal head position and neck pain.

 

2. PREPRATIONS

The preparations of BoNT-A marketed in the United States , the United Kingdom and Europe (Dysport, by Speywood-Vaccine and Research Laboratory-Porton Down; Salisbury, UK), and Japan (CS-BOT) differ in potency.
 BoNT-A is prepared by laboratory fermentation of C botulinum cultures. Crude botulinum toxin is a protein with a molecular weight of about 190,000 Daltons. After purification, the toxin is diluted with human serum albumin, bottled in vials, lyophilized (freeze-dried), and sealed.
 Each freeze-dried vial containing 100 units (U) of BoNT-A is reconstituted with preservative-free normal saline (1-5 mL) just before use. The manufacturer recommends that the toxin be used within 4 hours of reconstitution.
 The potency of BoNT-A is measured in mouse units (MU). One MU of BoNT-A is equivalent to the amount of toxin that kills 50% of a group of 20 g Swiss-Webster mice within 3 days of intraperitoneal injection (LD50).
 According to one report, 1 nanogram of toxin contains approximately 20 U of BOTOX® (ie, 1 U of BOTOX® is equal to approximately 0.05 nanogram of the toxin).
 According to another report comparing the 3 different preparations of BoNT-A, 1 nanogram of Dysport contains approximately 40 MU, whereas 1 nanogram of the BOTOX® contains approximately 4 MU, and 1 nanogram of CS-BOT contains approximately 15.2 MU.
 LD50 of BoNT-A for a 70-kg adult male has been calculated to be 2500-3000 U (35-40 U/kg).
 Minimum lethal dose of BoNT-B in monkeys is 2400 U/kg.
 Clinically, 1 U of BoNT-A is approximately equivalent to 3 U of Dysport.
 Standardization efforts are underway using measurements of the toxin's pharmacologically relevant actions (eg, median paralysis unit).
 BoNT-B is marketed in the United States as MyoBloc. This preparation is a ready-to-use solution that does not require reconstitution; it is available in 3 vial sizes (ie, 2500 U, 5000 U, and 10,000 U) and is stable for up to 21 months in refrigerator storage.

3. CLASSIFICATION
        Table-1. Types, Target, Discover of Botulinum toxin.
Type Target Discoverer Year
A SNAP-25 Landman 1904
B VAMP Ermengem 1897
C1 Syntaxin Bengston and Seldon 1922
D VAMP Robinson 1929
E SNAP-25 Gunnison 1936
F VAMP Moller and Scheibel 1960
G VAMP Gimenez and Ciccarelli 1970


• BoNT-A and BoNT-E cleave synaptosome-associated protein (SNAP-25), a presynaptic membrane protein required for fusion of neurotransmitter-containing vesicles.
• BoNT-B, BoNT-D, and BoNT-F cleave a vesicle-associated membrane protein (VAMP), also known as synaptobrevin.
• BoNT-C acts by cleaving syntaxin, a target membrane protein.
 
4. MECHANISAM OF ACTION
• A, Release of acetylcholine at the neuromuscular junction is mediated by the assembly of a synaptic fusion complex that allows the membrane of the synaptic vesicle containing acetylcholine to fuse with the neuronal cell membrane4.
• The synaptic fusion complex is a set of SNARE proteins, which include synaptobrevin, SNAP-25, and syntaxin4.
• After membrane fusion, acetylcholine is released into the synaptic cleft and then bound by receptors on the muscle cell.
• B, Botulinum toxin binds to the neuronal cell membrane at the nerve terminus and enters the neuron by endocytosis4.
• The light chain of botulinum toxin cleaves specific sites on the SNARE proteins, preventing complete assembly of the synaptic fusion complex and thereby blocking acetylcholine release. Botulinum toxins types B, D, F, and G cleave synaptobrevin; types A, C, and E cleave SNAP-25; and type C cleaves syntaxin4.
• Without acetylcholine release, the muscle is unable to contract. SNARE indicates soluble NSF-attachment protein receptor; NSF, N-ethylmaleimide-sensitive fusion protein; and SNAP-25, synaptosomal-associated protein of 25 kd4.
 
Fig. 1 Mechanism of action4 .

• Target molecules of botulinum (BoNT) and tetanus (TeNT) toxins inside the axon terminal.
• The heavy chain of the toxin is particularly important for targeting the toxin to specific types of axon terminals. The toxin must get inside the axon terminals in order to cause paralysis. Following the attachment of the toxin heavy chain to proteins on the surface of axon terminals, the toxin can be taken into neurons by endocytosis. The light chain is able to leave endocytotic vesicles and reach the cytoplasm. The light chain of the toxin has protease activity4.
• The type a toxin proteolytically degrades the SNAP-25 protein, a type of SNARE protein. The SNAP-25 protein is required for the release of neurotransmitters from the axon endings.[24] Botulinum toxin specifically cleaves these SNAREs, and so prevents neuro-secretory vesicles from docking/fusing with the nerve synapse plasma membrane and releasing their neurotransmitters4.
• Though it affects the nervous system, common nerve agent treatments (namely the injection of atropine and 2-pam-chloride) will increase mortality by enhancing botulin toxin's mechanism of toxicity32.
• Attacks involving botulinum toxin are distinguishable from those involving nerve agent in that NBC detection equipment (such as M-8 paper or the ICAM) will not indicate a "positive" when a sample of the agent is tested. Furthermore, botulism symptoms develop relatively slowly, over several days compared to nerve agent effects, which can be instantaneous.4,73

 
5. THERAPEUTIC USES


5.1. Focal dystonias - Involuntary, sustained, or spasmodic patterned muscle activity8, 14:
• Cervical dystonia (spasmodic torticollis)
• Blepharospasm (eyelid closure)
• Laryngeal dystonia (spasmodic dysphonia)
• Limb dystonia (writer's cramp)
• Oromandibular dystonia
• Orolingual dystonia
• Truncal dystonia
5.2. Spasticity - Velocity-dependent increase in muscle tone 14 -16 :
•  Stroke
•  Traumatic brain injury
•  Cerebral palsy
•  Multiple sclerosis
•  Spinal cord injury
5.3.    Nondystonic disorders of involuntary muscle activity 22, 26 :
• Hemifacial spasm
•  Tremor
•  Tics
•  Myokymia and synkinesis
•  Myoclonus (tensor veli palatini muscle [middle ear], causing tinnitus)
• Hereditary muscle cramps
5.4.     Strabismus (disorder of conjugate eye movement) and nystagmus33.
5.5.       Disorders of localized muscle spasms and pain42 :
• Chronic low back pain
• Myofascial pain syndrome
• Temporomandibular joint disorders associated with increased muscle activity
• Tension headache
•  Migraine headache
• Cervicogenic headache
5.6.    Smooth muscle hyperactive disorders34:
• Detrusor-sphincter dyssynergia
• Benign prostatic hypertrophy
•  Achalasia cardia
•  Hirschsprung disease
• Sphincter of Oddi dysfunctions
•  Following hemorrhoidectomy
•  Chronic anal fissures
5.7.     Cosmetic use 24
• Hyperkinetic facial lines (glabellar frown lines, crow's feet)
•  Hypertrophic platysma muscle bands
5.8.     Sweating disorders24, 36
• Axillary and palmar hyperhidrosis.
5.1.1. Botulinum Toxin Use in Dystonia 8-14
Use of BoNT different types of focal dystonias has been well studied and has proven to be very effective. Botulinum toxin injection is the treatment of choice for cervical dystonia (spasmodic torticollis). This injection benefits the highest percentage of patients in the shortest time and has been proven effective in many double-blind, placebo-controlled trials. Botulinum toxin injection has fewer side effects than do other pharmacologic treatments.
In a double-blind, placebo-controlled trial by Greene and colleagues, 55 patients who previously had failed to find relief in 2 trials of medication received either BoNT or placebo in a double-blinded fashion and were tracked for 12 weeks.6 Four weeks of open phase then followed when all patients received BoNT. By 6 weeks, 61% of patients showed improvement in head posture, and 39.5% reported reduction of pain. Both measures significantly improved (P <.05) compared to controls. During the open phase, patients who previously received placebo exhibited a similar response. Overall, 74% of patients improved by the end of the study.
A study by Brans and colleagues showed that in 64 patients with cervical dystonia, 84% reported long-term benefits in terms of impairment, disability, handicap, and quality of life.
5.1.1.1. Procedure:
Treatment dosages of BoNT-A in the United States have been reported to range from 100-300 U per patient. In a double-blind, placebo-controlled study, Poewe and colleagues demonstrated that magnitude and duration of improvement were greatest after injections of 1000 U of Dysport, but the injections caused significantly more adverse effects. The researchers recommended a lower starting dose of 500 U of Dysport (1 U of BoNT-A = 3 U of Dysport). One hundred U of toxin per mL of preservative-free normal saline are commonly used.
 Injections are performed with a Teflon-coated, 24-gauge needle connected to an electromyographic (EMG) machine. Those muscles with highest clinical and EMG activity are injected. Usually, 2-4 separate muscles are injected in 1 session and, in larger muscles, 2-4 sites per muscle are injected.
 No general consensus exists among users of BoNT regarding the need for EMG guidance while injecting the compound for cervical dystonia. EMG guidance, however, is helpful, particularly in obese patients whose neck muscles cannot adequately be palpated.
 Identifying the specific muscles involved in cervical dystonia prior to the injection is important. Those most commonly injected are the sternocleidomastoid, trapezius, splenius capitis, and levator scapulae muscles. An EMG study of 100 patients found that 2 or 3 muscles commonly are abnormal. Eighty-nine percent of patients with rotating torticollis had involvement of the ipsilateral splenius capitis and contralateral sternocleidomastoid with or without the additional involvement of the contralateral splenius capitis. Patients with laterocollis had ipsilateral sternocleidomastoid, splenius capitis, and trapezius involvement, while retrocollis was produced by bilateral splenius capitis activity.
 Beneficial effect from toxin injection usually is apparent in 7-10 days. Maximum response from the toxin is reached in approximately 4-6 weeks and lasts for an average of 12 weeks. Injections usually are repeated every 3-4 months.
5.1.1.2. Complications
 Neck weakness, dysphagia, and local pain at the injection site are the most commonly reported side effects. Other adverse effects (eg, local hematoma, generalized fatigue, lethargy, dizziness, dry mouth, dysphonia, flulike syndrome, pain in neighboring muscles) also have been reported.
 Most studies have reported side effects in 20-30% of patients per treatment cycle. The incidence of adverse effects varies based on the dosage used (ie, the higher the dose, the more frequent the adverse effects); however, Jankovic and Schwartz reported that incidence of complications was not related to the total dose of BoNT used. Women and patients who received injections into the sternocleidomastoid muscles had significantly higher rates of complications.
 Dysphagia has been the most prevalent significant complication and most probably is related to diffusion of the toxin into nearby pharyngeal muscles. In the study by Comella and colleagues, 33% of patients receiving their first dose of botulinum toxin experienced dysphagia. This complication most commonly occurs with injections of the sternocleidomastoid and can be reduced significantly when the dose of toxin administered is 100 U or less.
5.2.1. Botulinum Toxin Use in Spasticity13, 16, 20-22
 Spasticity is defined as a velocity-dependent increase in muscle tone. Intramuscular injections of BoNT have been studied and found to be useful in the treatment of spasticity in multiple sclerosis (MS), cerebral palsy (CP), stroke, traumatic brain injury (TBI), and spinal cord injury (SCI).                                
 
6. SIDE EFFECTS
The following side effects of Botulinum toxin9-14, 22: 
 Cervical Dystonia
  Primary Axillary Hyperhidrosis
  Blepharospasm
   Strabismus
  Immunogenicity
  Allergic reactions like skin rash, itching or hives, swelling of the face, lips.
  Breathing problems
  Changes in vision
  Chest pain or tightness
  Eye pain, infection
  Fast, irregular heartbeats
   Numbness
  Swallowing problems
   Side effects that usually do not require medical attention:
a)  Bruising or pain at site where injected
b)  Drooping eyelid
c)  Headache
d)   Nausea
e)  Sensitivity to light
f)   Tearing
6.1  Cervical Dystonia9-14
In cervical dystonia patients evaluated for safety in double-blind and open-label studies following injection of BOTOX® , the most frequently reported adverse reactions were dysphagia (19%), upper respiratory infection (12%), neck pain (11%), and headache (11%).7
Other events reported in 2-10% of patients in any one study in decreasing order of incidence include: increased cough, flu syndrome, back pain, rhinitis, dizziness, and hypertonia, soreness at injection site, asthenia, oral dryness, speech disorder, fever, nausea, and drowsiness. Stiffness, numbness, diplopia, ptosis, and dyspnea have been reported rarely.
Dysphagia and symptomatic general weakness may be attributable to an extension of the pharmacology of BOTOX® resulting from the spread of the toxin outside the injected muscles.
The most common severe adverse event associated with the use of BOTOX® injection in patients with cervical dystonia is dysphagia with about 20% of these cases also reporting dyspnea. Most dysphagia is reported as mild or moderate in severity. However, it may rarely be associated with more severe signs and symptoms.
Additionally reports in the literature include a case of a female patient who developed brachial plexopathy two days after injection of 120 Units of BOTOX® for the treatment of cervical dystonia, and reports of dysphonia in patients who have been treated for cervical dystonia.
6.2 Primary Axillary Hyperhidrosis14
The most frequently reported adverse events (3- 10% of patients) following injection of BOTOX® in double-blind studies included injection site pain and hemorrhage, non-axillary sweating, infection, pharyngitis, flu syndrome, headache, fever, neck or back pain, pruritus, and anxiety.
The data reflect 346 patients exposed to BOTOX® 50 Units and 110 patients exposed to BOTOX® 75 Units in each axilla. The clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not be predictive of rates observed in practice.
6.3 Blepharospasm46
In a study of blepharospasm patients who received an average dose per eye of 33 Units (injected at 3 to 5 sites) of the currently manufactured BOTOX® , the most frequently reported treatmentrelated adverse reactions were ptosis (20.8%), superficial punctate keratitis (6.3%) and eye dryness (6.3%).
In this study, the rate for ptosis in the current BOTOX® treated group (20.8% of patients) was significantly higher than the original BOTOX® treated group (4.0% of patients) (p=0.014%). All of these events were mild or moderate except for one case of ptosis which was rated severe.
Other events reported in prior clinical studies in decreasing order of incidence include: irritation, tearing, lagophthalmos, photophobia, ectropion, keratitis, diplopia and entropion, diffuse skin rash and local swelling of the eyelid skin lasting for several days following eyelid injection.
In two cases of VII nerve disorder (one case of an aphakic eye), reduced blinking from BOTOX® injection of the orbicularis muscle led to serious corneal exposure, persistent epithelial defect, and corneal ulceration. Perforation occurred in the aphakic eye and required corneal grafting.
A report of acute angle closure glaucoma one day after receiving an injection of botulinum toxin for blepharospasm was received, with recovery four months later after laser iridotomy and trabeculectomy. Focal facial paralysis, syncope and exacerbation of myasthenia gravis have also been reported after treatment of blepharospasm.
6.4 Strabismus42 
Extraocular muscles adjacent to the injection site can be affected, causing ptosis or vertical deviation, especially with higher doses of BOTOX®. The incidence rates of these adverse effects in 2058 adults who received a total of 3650 injections for horizontal strabismus are 15.7% and 16.9%, respectively.
Inducing paralysis in one or more extraocular muscles may produce spatial disorientation, double vision, or past-pointing. Covering the affected eye may alleviate these symptoms.
The incidence of ptosis was 0.9% after inferior rectus injection and 37.7% after superior rectus injection.
Ptosis (0.3%) and vertical deviation greater than two prism diopters (2.1%) were reported to persist for over six months in a larger series of 5587 injections of horizontal muscles in 3104 patients.
In these patients, the injection procedure itself caused nine scleral perforations. A vitreous hemorrhage occurred in one case and later cleared. No retinal detachment or visual loss occurred in any case. Sixteen retrobulbar hemorrhages occurred without visual loss. Decompression of the orbit after five minutes was done to restore retinal circulation in one case. Five eyes had pupillary change consistent with ciliary ganglion damage (Adie's pupil).
One patient developed anterior segment ischemia after receiving BOTOX® injection into the medial rectus muscle under direct visualization for esotropia.
6.5 Immunogenicity44
Formation of neutralizing antibodies to botulinum toxin type A may reduce the effectiveness of BOTOX® treatment by inactivating the biological activity of the toxin. The rate of formation of neutralizing antibodies in patients receiving BOTOX® has not been well studied.
In the phase 3 cervical dystonia study that enrolled only patients with a history of receiving BOTOX® for multiple treatment sessions, at study entry there were 192 patients with antibody assay results, of whom 33 (17%) had a positive assay for neutralizing activity. There were 96 patients in the randomized period of the phase 3 studies with valid assays at both study entry and end and who were neutralizing activity negative at entry. Of these 96, 2 patients (2%) converted to positive for neutralizing activity. Both of these converting patients were among the 52 who had received two BOTOX® treatments between the two assays; none were in the group randomized to placebo in the controlled comparison period of the study.
In the randomized period of the cervical dystonia study, patients in the BOTOX® group whose baseline assays were neutralizing antibody negative showed improvements on CDSS (n=64, mean CDSS change -2.1) while patients whose baseline assays were neutralizing antibody positive did not (n=14, mean CDSS change +1.1). However, in uncontrolled studies there are also individual patients who are perceived as continuing to respond to treatments despite the presence of neutralizing activity. Not all patients who become non-responsive to BOTOX® after an initial period of clinical response have demonstrable levels of neutralizing activity.
One patient among the 445 hyperidrosis patients with analyzed specimens showed the presence of neutralizing antibodies.
The data reflect the patients whose test results were considered positive or negative for neutralizing activity to BOTOX® in a mouse protection assay. The results of these tests are highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of neutralizing activity in an assay may be influenced by several factors including sample handling, concomitant medications and underlying disease.

7. DRUG INTERACTIONS

Co-administration of BOTOX® and aminoglycosides or other agents interfering with neuromuscular transmission (e.g., curare-like compounds) should only be performed with caution as the effect of the toxin may be potentiated.
 The effect of administering different botulinum neurotoxin serotypes at the same time or within several months of each other is unknown. Excessive neuromuscular weakness may be exacerbated by administration of another botulinum toxin prior to the resolution of the effects of a previously administered botulinum toxin.
 Pregnancy: Pregnancy Category C
 
8. TYPES OF BOTULINUM POISONING

There are three types of botulism poisoning, distinguished by the manner in which they are contracted14, 46,:
1. Food borne botulinum poisoning.
2. Wound botulinum poisoning.
3. Intestinal (infant and adult) botulinum poisoning.

8.1 Food borne botulinum poisoning14: In the food-borne form of the disease, the person ingests the toxin itself by eating food contaminated with it. But the public still generally associates botulism with food poisoning in adults and children. The food-borne disease is the most avoidable form of botulism.
Symptoms usually develop within a day of eating the food, although they can take up to 10 days to manifest. Apart from weakness and paralysis, common complaints include fatigue, dry mouth, and difficulty swallowing. Unfortunately, doctors sometimes misdiagnose the symptoms as Guillain-Barré syndrome, stroke, intoxication, or a handful of other conditions. For this reason, federal health officials suspect that botulism poisoning is under diagnosed.
 Home Canning: One of the most common culprits in food-borne botulism is home-canned food, especially vegetables such as asparagus, green beans, and peppers. More than 90 percent of food-borne botulism outbreaks between 1976 and 1985 were due to home-processed foods. One basic recommendation is to cook food to be canned in pressure cookers because they can maintain temperatures high enough (above 212 F, or 100 C) for 10 minutes to kill the spores, which are remarkably heat-resistant.
 Foods cooked at home should not be left at temperatures between 40 F and 140 F (4.5 C to 60 C) for more than four hours. Toxin that may have formed can readily be destroyed by boiling the food for 10 minutes.
 Commercial foods have also been involved in botulism outbreaks. Some outbreaks have been attributed to improperly handled food, such as potato salad, served in restaurants. But many commercial food outbreaks are due to consumer mishandling, such as disregarding labels that indicate the food should be refrigerated. Some food companies acidify their products or lower their moisture content as an extra precautionary measure in case the refrigeration warning is not heeded. Consumers can best protect themselves by reading the labels and following the storage instructions, Swanson says, and by discarding rusty, swollen or otherwise damaged cans.
8.2 Wound botulinum poisoning20: In wound botulism, which is very rare, the toxin is produced by C. botulinum bacteria in an infected wound. Statistically, infant botulism, which was recognized in the mid-'70s, is the most common form of the disease.

8.3 Intestinal (infant and adult) botulinum poisoning34: Infant botulism differs from food-borne botulism in that the toxin itself is not ingested. Instead, C. botulinum spores swallowed by the infant germinate and produce the toxin in the favorable environment of the baby's large intestine.
Because the spores are nearly everywhere in the environment, children and adults regularly ingest them, yet very rarely suffer ill effects. In a few cases, adults who have had intestinal surgery or whose intestinal tracts have otherwise been altered have contracted the disease the way infants do. This has led researchers to conclude that infants' as-yet "incompletely-developed intestinal flora," may be to blame, says Arnon, one of the co-discoverers of infant botulism in 1976.
Infant botulism is serious, but rare and not usually fatal. From 1976 through the end of 1993, 1,206 infant botulism cases were confirmed in the United States. About 75 to 100 cases are reported annually, about half of them in California (presumed to be due to the prevalence of C. botulinum spores in the state, its high number of births, and the pediatric community's familiarity with the disease, which results in more correct botulism diagnoses). All of the infant cases involve babies less than 1 year old; the disease is most common in the second month of life.
Infants' immature intestinal tracts offer a "window of vulnerability, and if a baby has the bad luck to swallow a botulism spore during that period, the spore has an opportunity to germinate," Arnon says. The spores travel with microscopic dust particles, so the researchers have concluded that most affected infants have simply inhaled the spores. "They mix with saliva, they're swallowed, and that's how they reach the intestine," Arnon says. Unfortunately, there is no way to prevent the disease in such cases.
But parents and other caregivers can prevent babies acquiring infant botulism from one source--honey. California researchers have isolated C. botulinum spores from about 10 percent of store-bought honey samples, and although less than 5 percent of infant botulism patients contract the disease from honey, health officials and pediatricians agree that honey should not be fed to infants less than 1 year of age (it is perfectly safe for older children and adults).
The first sign that an infant has botulism is usually constipation, although this isn't always apparent to parents. Often the baby isn't brought to a doctor until parents notice other symptoms, such as lethargy and poor feeding as the paralysis begins to affect the baby's gag reflex and swallowing ability.
Because breathing is affected in the most severe stage of botulism-induced paralysis, researchers suspect a link between infant botulism and sudden infant death syndrome (SIDS), also known as crib death. One study done 15 years ago showed that about 5 percent of children in California whose deaths were attributed to SIDS actually had died from infant botulism. Because of the difficulty of conducting such studies, the link between SIDS and infant botulism remains poorly understood.
The infant botulism fatality rate is less than 2 percent, and recovery is usually complete. Often, however, infants have to spend weeks or months on a ventilator. Horse-derived antitoxin is not given to infants because of the risk of side effects such as anaphylaxis and serum sickness. But in February 1992, the California Department of Health Services began a new clinical trial that may provide a way of lessening the effects of the disease.
With funds from the FDA's Orphan Products Grants Program, the trial is evaluating a human-derived antitoxin obtained from laboratory workers who for occupational safety reasons have been immunized with botulinum toxoid, which is toxin whose poisoning potential has been removed.
The California investigators will assess whether infants given the antitoxin will have shorter hospital stays, fewer complications, and a halt to the progression of disease. Infant botulism represents the only opportunity to evaluate the safety and efficacy of human-derived botulism antitoxin (known formally as Botulism Immune Globulin) because of the sporadic and even less frequent occurrence of food-borne and wound botulism.

9. TREATMENT OF BOTULINUM POISIONING
The case fatality rate for botulinum poisoning between 1950 and 1996 was 15.5%, down from approximately 60% over the previous 50 years. Death is generally secondary to respiratory failure due to paralysis of the respiratory muscles, so treatment consists of antitoxin administration and artificial ventilation. If initiated on time, these are quite effective. Occasionally, functional recovery may take several weeks to months44.
9.1 There are two primary Botulinum Antitoxins available for treatment of botulism.44-46
1. Trivalent (A, B, E) Botulinum Antitoxin is derived from equine sources utilizing          whole antibodies (Fab & Fc portions). This antitoxin is available from the local health department via the CDC.
2. The second antitoxin is Heptavalent (A,B,C,D,E,F,G) Botulinum Antitoxin which is derived from "despeciated" equine IgG antibodies which have had the Fc portion cleaved off leaving the F(ab')2 portions. This is a less immunogenic antitoxin that is effective against all known strains of botulism where not contraindicated. This is available from the US Army. On June 1, 2006 the US Department of Health and Human Services awarded a $363 million contract with Cangene Corporation for 200,000 doses of Heptavalent Botulinum Antitoxin over five years for delivery into the Strategic National Stockpile beginning in 2007.

10. DOSAGE AND ADMINISTRATION
 Botulinum toxin is giving by injection. Dosing should be individualized, and the lowest effective dose should be used. In a study that investigated the use of botulinum toxin in treating cervical dystonia the median total dose was 236 U divided between the affected muscles54  .
For the treatment of blepharospasm the recommended initial dose is 1.25 to 2.5 U injected into the medial and lateral pre-tarsal orbicularis oculi, the muscle of the upper and lower eyelid. Effects are seen within three days and peak within one to two weeks. Effects may last up to three months after which the treatment may be repeated. If the initial response is inadequate, the dose may be increased two-fold. Injecting more than 5 U is not increasingly beneficial55.
In the treatment of strabismus, the initial dose is 1.25-5 U depending on the severity of the strabismus. Muscle paralysis may occur within one to two days after the injection and may last for 2-6 weeks. Treatment should be assessed every 7-14 days after an injection, and, if there is an adequate response, the same dose can be continued. If the response is not adequate, the dose can be increased two-fold55 .
The total treatment dose for glabellar lines is 20 units. The lowest effective dose should be used, and treatment should not be more frequent than every three months55.

 11. OVERDOSE AND STORAGE
  11.1 Overdose: Signs and symptoms of overdose are not apparent immediately post-injection. Should accidental injection or oral ingestion occur, the person should be medically supervised for up to several weeks for signs or symptoms of systemic weakness or muscle paralysis.73
An antitoxin is available in the event of immediate knowledge of an overdose or misinjection. In the event of an overdose or injection into the wrong muscle, immediately contact Allergan for additional information at (800) 433-8871 from 7:00 am to 3:00 pm Pacific Standard Time, or at (714) 246-5954 for a recorded message at other times. The antitoxin will not reverse any botulinum toxin induced muscle weakness effects already apparent by the time of antitoxin administration73.
11.2 Storage: Unopened vials of botulinum toxin should be refrigerated at 2-8°C; Reconstituted toxin should be used within 4 hours.73

 

12. POSITION IN INDIA
Botulinum toxin type A is available at a cost of about Indian Rs.15000/- per vial. A typical child with spastic calf muscles would need about 1 vial at a sitting, usually to correct equines deformity of foot or severe scissoring, to be repeated months later when he relapses. An inferior but cheap alternative is Phenol Nerve Block (about $17 per vial), which is still used in developing countries due to economic considerations. It gives temporary relief of spasticity but may cause paraesthesias and muscle damage if used repeatedly73.
A few centres in India are using these injections now and then for CP but their long term benefits are open to discussion.73
12.1. GENERIC NAME73
• Botulinum Toxic Type A.
12.2. BRAND NAME73
• BTX,
• BTX,
• BoNT,
• Dysport,
• CS-BOT,
• NeuroBloc,
• MyoBloc,
• BotB,
• BOTOX® injection,

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