Doloracin/L Rx with Lidocaine

Doloracin/L Rx with Lidocaine Uses, Dosage, Side Effects, Food Interaction and all others data.

Although the precise mechanism of action of Capsaicin is not fully understood, current evidence suggests that Capsaicin exerts an analgesic effect by depleting and preventing reaccumulation of Substance P in peripheral sensory neurons. Substance P is thought to be the principal chemomediator of pain impulses from the periphery to the central nervous system.

Capsaicin is a TRPV1 receptor agonist. TRPV1 is a trans-membrane receptor-ion channel complex activated by temperatures higher than 43 degrees Celsius, pH lower than 6, and endogenous lipids. When activated by a combination of these factors, the channel can transiently open and initiate depolarization due to the influx of calcium and sodium ions. Because TRPV1 is commonly expressed in A-delta and mostly C fibers, depolarization results in action potentials which send impulses to the brain and spinal cord. These impulses result in capsaicin effects of warming, tingling, itching, stinging, or burning. Capsaicin also causes more persistent activation of these receptors compared to the environmental agonists, resulting in a loss of response to many sensory stimuli, described as "defunctionalization". Capsaicin is associated with many enzymatic, cytoskeletal, and osmotic changes, as well as disruption of mitochondrial respiration, impairing nociceptor function for extended periods of time.

Lidocaine is an amide type local anaesth. It stabilises the neuronal membrane and inhibits Na ion movements, which are necessary for conduction of impulses. In the heart, lidocaine reduces depolarisation of the ventricles during diastole and automaticity in the His-Purkinje system. Duration of action potential and effective refractory period are also reduced.

Excessive blood levels of lidocaine can cause changes in cardiac output, total peripheral resistance, and mean arterial pressure . With central neural blockade these changes may be attributable to the block of autonomic fibers, a direct depressant effect of the local anesthetic agent on various components of the cardiovascular system, and/or the beta-adrenergic receptor stimulating action of epinephrine when present . The net effect is normally a modest hypotension when the recommended dosages are not exceeded .

In particular, such cardiac effects are likely associated with the principal effect that lidocaine elicits when it binds and blocks sodium channels, inhibiting the ionic fluxes required for the initiation and conduction of electrical action potential impulses necessary to facilitate muscle contraction . Subsequently, in cardiac myocytes, lidocaine can potentially block or otherwise slow the rise of cardiac action potentials and their associated cardiac myocyte contractions, resulting in possible effects like hypotension, bradycardia, myocardial depression, cardiac arrhythmias, and perhaps cardiac arrest or circulatory collapse .

Moreover, lidocaine possesses a dissociation constant (pKa) of 7.7 and is considered a weak base . As a result, about 25% of lidocaine molecules will be un-ionized and available at the physiological pH of 7.4 to translocate inside nerve cells, which means lidocaine elicits an onset of action more rapidly than other local anesthetics that have higher pKa values . This rapid onset of action is demonstrated in about one minute following intravenous injection and fifteen minutes following intramuscular injection . The administered lidocaine subsequently spreads rapidly through the surrounding tissues and the anesthetic effect lasts approximately ten to twenty minutes when given intravenously and about sixty to ninety minutes after intramuscular injection .

Methyl salicylate (oil of wintergreen or wintergreen oil) is an organic ester naturally produced by many species of plants, particularly wintergreens. The compound was first extracted and isolated from plant species Gaultheria procumbens in 1843. It can be manufactured synthetically and it used as a fragrance, in foods, beverages, and liniments. It forms a colorless to yellow or reddish liquid and exhibits a characteristic odor and taste of wintergreen. For acute joint and muscular pain, methyl salicylate is used as a rubefacient and analgesic in deep heating liniments. It is used as a flavoring agent in chewing gums and mints in small concentrations and added as antiseptic in mouthwash solutions.

Methyl salicylate relieve musculoskeletal pain in the muscles, joints, and tendons by causing irritation and reddening of the skin due to dilated capillaries and increased blood flow. It is pharmacologically similar to aspirin and other NSAIDs but as a topical agent it primarily acts as a rubefacient and skin irritant. Counter-irritation is believed to cause a soothing sensation of warmth.

Doloracin/L Rx with Lidocaine
Uses
Dosage
Side Effect
Precautions
Interactions
Uses during Pregnancy
Uses during Breastfeeding
Accute Overdose
Food Interaction
Half Life
Volume of Distribution
Clearance
Interaction With other Medicine
Contradiction
Storage

Trade Name	Doloracin/L Rx with Lidocaine
Generic	Methyl salicylate + menthol + capsaicin + lidocaine
Type	Cream
Therapeutic Class
Manufacturer
Available Country	United States
Last Updated:	September 19, 2023 at 7:00 am

Uses

Capsaicin is indicatd for- Rheumatoid arthritis, Osteoarthritis, Pain due to diabetic neuropathy, Joint pain, Post-herpetic neuralgia, Post-surgical neuropathic pain, Nerve Pain, Back pain, Muscle pain, Fibromyalgia, Bursitis, Pruritis (itching)

Lidocaine is a topical anesthetic used for the following purposes-

To help prevent pain associated with minor surgical procedures in the ear, nose and throat
To help prevent pain and or discomfort during dental procedures (e.g., prior to an injection)
During general anesthesia to prevent coughing
To help prevent pain during the final stages of childbirth, before the cutting or stitching of the perineum (skin between the vagina and anus)

Methyl salicylate is a topical counter-irritant used for the symptomatic relief of acute musculoskeletal pain in the muscles, joints, and tendons.

Ointments or liniments containing methyl salicylate are applied topically as counter irritant for relief of acute pain associated with lumbago,sciatica and rheumatic conditions. Local analgesics for human and veterinary medicine.

Doloracin/L Rx with Lidocaine is also used to associated treatment for these conditions: Arthritis, Back Pain Lower Back, Backache, Bursitis, Contusions, Inflammatory Reaction caused by Rheumatism, Muscle Cramps, Musculoskeletal Pain, Osteoarthritis (OA), Periarthritis, Post-Herpetic Neuralgia (PHN), Rheumatic Pain, Soft Tissue Injury, Tendinitis, Acute nonspecific tenosynovitisAcute Otitis Media, Anal Fissures, Anorectal discomfort, Arrhythmia, Back Pain Lower Back, Bacterial Vaginosis (BV), Burns, Cervical Syndrome, Earache, Hemorrhoids, Infection, Inflammatory Reaction caused by ear infection-not otherwise specified, Insect Bites, Joint Pain, Mixed Vaginal Infections, Multiple Myeloma (MM), Myringitis, Neuritis, Osteolysis caused by Bone Tumors, Osteoporosis, Otitis Externa, Pain caused by ear infection-not otherwise specified, Pain, Inflammatory, Post-Herpetic Neuralgia (PHN), Postherpetic Neuralgia, Primary Hyperparathyroidism, Rheumatic Diseases, Rheumatic Joint Disease, Sciatica, Skin Irritation, Soft Tissue Inflammation, Sore Throat, Sunburn, Susceptible infections, Trichomonas Vaginitis, Ulcers, Leg, Urethral Strictures, Vulvovaginal Candidiasis, Abrasions, Anal discomfort, Arrhythmia of ventricular origin, Cutaneous lesions, Gum pain, Minor burns, Superficial Wounds, Susceptible Bacterial Infections, Ulceration of the mouth, Viral infections of the external ear canal, Post Myocardial Infarction Treatment, Regional Anesthesia, Local anesthesia therapyAcute Muscle Pain, Arthritis, Back Pain Lower Back, Backache, Contusions, Joint Pain, Ligament pain, Muscle Inflammation, Muscle Injuries, Muscle Strain, Muscle swelling, Pain, Pain of the Bone and Bones, Pain, Nerve, Partial-Onset Seizures, Postherpetic Neuralgia, Soreness, Muscle, Sprains, Tendon pain, Minor aches, Muscle, joint pains

How Doloracin/L Rx with Lidocaine works

Capsaicin has been shown to reduce the amount of substance P associated with inflammation - however this is not believed to be its main mechanism in the relief of pain . Capsaicin's mechanism of action is attributed to "defunctionalization" of nociceptor fibers by inducing a topical hypersensitivity reaction on the skin. This alteration in pain mechanisms is due to many of the following: temporary loss of membrane potential, inability to transport neurotrophic factors leading to altered phenotype, and reversible retraction of epidermal and dermal nerve fiber terminals.

Lidocaine is a local anesthetic of the amide type . It is used to provide local anesthesia by nerve blockade at various sites in the body . It does so by stabilizing the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby effecting local anesthetic action . In particular, the lidocaine agent acts on sodium ion channels located on the internal surface of nerve cell membranes . At these channels, neutral uncharged lidocaine molecules diffuse through neural sheaths into the axoplasm where they are subsequently ionized by joining with hydrogen ions . The resultant lidocaine cations are then capable of reversibly binding the sodium channels from the inside, keeping them locked in an open state that prevents nerve depolarization . As a result, with sufficient blockage, the membrane of the postsynaptic neuron will ultimately not depolarize and will thus fail to transmit an action potential . This facilitates an anesthetic effect by not merely preventing pain signals from propagating to the brain but by aborting their generation in the first place .

In addition to blocking conduction in nerve axons in the peripheral nervous system, lidocaine has important effects on the central nervous system and cardiovascular system . After absorption, lidocaine may cause stimulation of the CNS followed by depression and in the cardiovascular system, it acts primarily on the myocardium where it may produce decreases in electrical excitability, conduction rate, and force of contraction .

Counter-irritation is thought to be effective at alleviating musculoskeletal pain as the irritation of the sensory nerve endings is thought to alter or offset pain in the underlying muscle or joints that are served by the same nerves . This is thought to mask the underlying musculoskeletal pain and discomfort. When applied topically, methyl salicylate is thought to penetrate the skin and underlying tissues where it reversibly inhibits cyclooxygenase enzyme and locally and peripherally prevents the production of inflammatory mediators such as prostaglandin and thromboxane A2.

Dosage

Doloracin/L Rx with Lidocaine dosage

18 years of age and older:Apply a thin film of Capsaicin cream to affected area 3 to 4 times daily. A burning sensation may occur upon application, but generally disappears with regular use. Application schedules of 3 to 4 times a day for 2 weeks provides optimum pain relief.

Intramuscular:Emergency treatment of ventricular arrhythmias: 300 mg injected into the deltoid muscle, repeat after 60-90 min if necessary.

Intraspinal:Spinal anaesthesia: As hyperbaric soln of 1.5% or 5% lidocaine in 7.5% glucose soln. Normal vaginal delivery: Up to 50 mg (as 5% soln) or 9-15 mg (as 1.5% soln). Caesarian operation: Up to 75 mg (as 5% soln). Other surgical procedures: 75-100 mg.Intravenous:Pulseless ventricular fibrillation or ventricular tachycardia : 1-1.5 mg/kg repeated as necessary. Max: 3 mg/kg. For ventricular arrhythmias in more stable patients: Usual loading dose: 50-100 mg as an IV inj at 25-50 mg/min, may repeat once or twice up to a max of 200-300 mg in 1 hr, followed by 1-4 mg/min via continuous IV infusion. May need to reduce dose if the infusion is longer than 24 hr.

Intravenous:Intravenous regional anaesthesia: As 0.5% soln w/o epinephrine: 50-300 mg. Max: 4 mg/kg.

Parenteral:Percutaneous infiltration anaesthesia: As 0.5% or 1% soln: 5-300 mg.Sympathetic nerve block: As 1% soln: 50 mg for cervical block or 50-100 mg for lumbar block.Peripheral nerve block:

As 1.5% soln: For brachial plexus block: 225-300 mg.
As 2% soln: For dental nerve block: 20-100 mg.
As 1% soln: For intercostal nerve block: 30 mg;
For paracervical block: 100 mg on each side, repeated not more frequently than every 90 min;
For paravertebral block: 30-50 mg;
For pudendal block: 100 mg on each side.
As 4% soln: For retrobulbar block: 120-200 mg.

Spray:

The maximum dose is 200 mg (Approximately 20 spray).
In dentistry, the normal dose is 1-5 sprays. Two sprays per quarter of the mouth is recommended, with a maximum of 3 sprays per quarter of the mouth over 30 minutes.
In sinus procedures 3 sprays are used.
In procedures of the throat and windpipe, up to 20 sprays may be necessary.
Up to 20 sprays may be necessary in childbirth (cesarian procedure).
Lower doses are used for children aged 3-12 years. Lidocaine 10% Spray is not recommended for children under 3 years.

Topical: Anaesthesia before e.g. venepuncture (not for infants), apply a thick layer under an occlusive dressing 1-5 hours before procedure; split skin grafting, apply a thick layer under an occlusive dressing 2-5 hours before procedure; genital warts (not for children), apply up to 10 gm 5-10 minutes before removal.

Side Effects

Capsaicin may cause transient burning on application. This burning is observed more frequently when the application schedules are more than 3-4 times daily. The burning can be enhanced if too much cream is used and if it is applied just before or after a bath or shower.

Arrhythmia, bradycardia, arterial spasms, CV collapse, oedema, flushing, hert block, hypotension, sinus node suppression, agitation, anxiety, coma, confusion, drowsiness, hallucinations, euphoria, headache, hyperaesthesia, hypoaesthesia, lightheadedness, lethargy, nervousness, psychosis, seizure, slurred speech, unconsciousness, somnolence, nausea, vomiting, metallic taste, tinnitus, disorientation, dizziness, paraesthesia, resp depression and convulsions. Patch: Bruising, depigmentation, petechiae, irritation. Ophth: Conjunctival hyperaemia, corneal epithelial changes, diplopia,visual changes.

Toxicity

Acute oral LD50 and dermal LD50 in mouse are 47.2 mg/kg and >512 mg/kg, respectively . Capsaicin is shown to be mutagenic for bacteria and yeast .

Capsaicin can cause serious irritation, conjunctivitis and lacrimation via contact with eyes. It induces a burning sensation and pain in case of contact with eyes and skin. As it is also irritating to the respiratory system, it causes lung irritation and coughing as well as bronchoconstriction. Other respiratory effects include laryngospasm, swelling of the larynx and lungs, chemical pneumonitis,respiratory arrest and central nervous system effects such as convulsions and excitement . In case of ingestion, gastrointestinal tract irritation may be observed along with a sensation of warmth or painful burning . Symptoms of systemic toxicity include disorientation, fear, loss of body motor control including diminished hand-eye coordination, hyperventilation, tachycardia, and pulmonary oedema . Careful early decontamination is recommended and medical intervention should be initiated for any life-threatening symptoms. In case of contact, individual must be removed from the source of exposure and the contacted skin and mucous membranes should be thoroughly washed with copious amounts of water .

Symptoms of overdose and/or acute systemic toxicity involves central nervous system toxicity that presents with symptoms of increasing severity . Patients may present initially with circumoral paraesthesia, numbness of the tongue, light-headedness, hyperacusis, and tinnitus . Visual disturbance and muscular tremors or muscle twitching are more serious and precede the onset of generalized convulsions . These signs must not be mistaken for neurotic behavior . Unconsciousness and grand mal convulsions may follow, which may last from a few seconds to several minutes . Hypoxia and hypercapnia occur rapidly following convulsions due to increased muscular activity, together with the interference with normal respiration and loss of the airway . In severe cases, apnoea may occur. Acidosis increases the toxic effects of local anesthetics . Effects on the cardiovascular system may be seen in severe cases . Hypotension, bradycardia, arrhythmia and cardiac arrest may occur as a result of high systemic concentrations, with potentially fatal outcome .

Pregnancy Category B has been established for the use of lidocaine in pregnancy, although there are no formal, adequate, and well-controlled studies in pregnant women . General consideration should be given to this fact before administering lidocaine to women of childbearing potential, especially during early pregnancy when maximum organogenesis takes place . Ultimately, although animal studies have revealed no evidence of harm to the fetus, lidocaine should not be administered during early pregnancy unless the benefits are considered to outweigh the risks . Lidocaine readily crosses the placental barrier after epidural or intravenous administration to the mother . The ratio of umbilical to maternal venous concentration is 0.5 to 0.6 . The fetus appears to be capable of metabolizing lidocaine at term . The elimination half-life in the newborn of the drug received in utero is about three hours, compared with 100 minutes in the adult . Elevated lidocaine levels may persist in the newborn for at least 48 hours after delivery . Fetal bradycardia or tachycardia, neonatal bradycardia, hypotonia or respiratory depression may occur .

Local anesthetics rapidly cross the placenta and when used for epidural, paracervical, pudendal or caudal block anesthesia, can cause varying degrees of maternal, fetal and neonatal toxicity . The potential for toxicity depends upon the procedure performed, the type and amount of drug used, and the technique of drug administration . Adverse reactions in the parturient, fetus and neonate involve alterations of the central nervous system, peripheral vascular tone, and cardiac function .

Maternal hypotension has resulted from regional anesthesia . Local anesthetics produce vasodilation by blocking sympathetic nerves . Elevating the patient’s legs and positioning her on her left side will help prevent decreases in blood pressure . The fetal heart rate also should be monitored continuously, and electronic fetal monitoring is highly advisable .

Epidural, spinal, paracervical, or pudendal anesthesia may alter the forces of parturition through changes in uterine contractility or maternal expulsive efforts . In one study, paracervical block anesthesia was associated with a decrease in the mean duration of first stage labor and facilitation of cervical dilation . However, spinal and epidural anesthesia have also been reported to prolong the second stage of labor by removing the parturient’s reflex urge to bear down or by interfering with motor function . The use of obstetrical anesthesia may increase the need for forceps assistance .

The use of some local anesthetic drug products during labor and delivery may be followed by diminished muscle strength and tone for the first day or two of life . The long-term significance of these observations is unknown . Fetal bradycardia may occur in 20 to 30 percent of patients receiving paracervical nerve block anesthesia with the amide-type local anesthetics and may be associated with fetal acidosis . Fetal heart rate should always be monitored during paracervical anesthesia . The physician should weigh the possible advantages against risks when considering a paracervical block in prematurity, toxemia of pregnancy, and fetal distress . Careful adherence to the recommended dosage is of the utmost importance in obstetrical paracervical block . Failure to achieve adequate analgesia with recommended doses should arouse suspicion of intravascular or fetal intracranial injection . Cases compatible with unintended fetal intracranial injection of local anesthetic solution have been reported following intended paracervical or pudendal block or both. Babies so affected present with unexplained neonatal depression at birth, which correlates with high local anesthetic serum levels, and often manifest seizures within six hours . Prompt use of supportive measures combined with forced urinary excretion of the local anesthetic has been used successfully to manage this complication .

It is not known whether this drug is excreted in human milk . Because many drugs are excreted in human milk, caution should be exercised when lidocaine is administered to a nursing woman .

Dosages in children should be reduced, commensurate with age, body weight and physical condition .

The oral LD 50 of lidocaine HCl in non-fasted female rats is 459 (346-773) mg/kg (as the salt) and 214 (159-324) mg/kg (as the salt) in fasted female rats .

Oral LD50 values (mg/kg) for mouse, rat and rabbit are 1110, 887 and 1300, respectively. Oral LD50 values for child and adult human (mg/kg) are 228 and 506, respectively. Although systemic toxicity from topical administration is rare, methyl salicylate can be absorbed in intract skin to cause stimulation of the central nervous system respiratory center, disturbance of lipid and carbohydrate metabolism, and disturbance of intracellular respiration. Severe toxicity can result in acute lung injury, lethargy, coma, seizures, cerebral edema, and death. In case of salicylate poisoning, the treatment consists of general supportive care, gastrointestinal decontamination with activated charcoal in cases of salicylate ingestion, and monitoring of serum salicylate concentrations. Bicarbonate infusions or hemodialysis can be used to achieve enhanced salicylate elimination .

Precaution

Capsaicin cream should not be applied to broken or irritated skin. Applied area should not be tightly bandaged. Do not get on mucous membranes and into eyes or on contact lenses. If this occurs, rinse the affected area thoroughly with water. Do not apply the cream on the heat treated area as this may increase the burning sensation. In case of accidental ingestion, seek physician advice immediately.

Patient with pseudocholinesterase deficiency, resp depression. Hepatic and renal impairment. Elderly or debilitated patients. Pregnancy and lactation.

Interaction

May increase serum levels with cimetidine and propranolol. Increased risk of cardiac depression with β-blockers and other antiarrhythmics. Additive cardiac effects with IV phenytoin. Hypokalaemia caused by acetazolamide, loop diuretics and thiazides may antagonise effect of lidocaine. Dose requirements may be increased with long-term use of phenytoin and other enzyme-inducers.

Volume of Distribution

The volume of distribution determined for lidocaine is 0.7 to 1.5 L/kg .

In particular, lidocaine is distributed throughout the total body water . Its rate of disappearance from the blood can be described by a two or possibly even three-compartment model . There is a rapid disappearance (alpha phase) which is believed to be related to uptake by rapidly equilibrating tissues (tissues with high vascular perfusion, for example) . The slower phase is related to distribution to slowly equilibrating tissues (beta phase) and to its metabolism and excretion (gamma phase) .

Lidocaine's distribution is ultimately throughout all body tissues . In general, the more highly perfused organs will show higher concentrations of the agent . The highest percentage of this drug will be found in skeletal muscle, mainly due to the mass of muscle rather than an affinity .

After absorption, methyl salicylate is distributed throughout most body tissues and most transcellular fluids, primarily by pH dependent passive processes. Salicylate is actively transported by a low-capacity, saturable system out of the CSF across the choroid plexus. The drug readily crosses the placental barrier.

Elimination Route

Oral: Following oral administration, capsaicin may be absorbed by a nonactive process from the stomach and whole intestine with an extent of absorption ranging between 50 and 90%, depending on the animal . The peak blood concentration can be reached within 1 hour following administration . Capsaicin may undergo minor metabolism in the small intestine epithelial cells post-absorption from the stomach into the small intestines. While oral pharmacokinetics information in humans is limited, ingestion of equipotent dose of 26.6 mg of pure capsaicin, capsaicin was detected in the plasma after 10 minutes and the peak plasma concentration of 2.47 ± 0.13 ng/ml was reached at 47.1 ± 2.0 minutes .

Systemic: Following intravenous or subcutaneous administration in animals, the concentrations in the brain and spinal cord were approximately 5-fold higher than that in blood and the concentration in the liver was approximately 3-fold higher than that in blood .

Topical: Topical capsaicin in humans is rapidly and well absorbed through the skin, however systemic absorption following topical or transdermal administration is unlikely . For patients receiving the topical patch containing 179 mg of capsaicin, a population analysis was performed and plasma concentrations of capsaicin were fitted using a one-compartment model with first-order absorption and linear elimination. The mean peak plasma concentration was 1.86 ng/mL but the maximum value observed in any patient was 17.8 ng/mL .

In general, lidocaine is readily absorbed across mucous membranes and damaged skin but poorly through intact skin . The agent is quickly absorbed from the upper airway, tracheobronchial tree, and alveoli into the bloodstream . And although lidocaine is also well absorbed across the gastrointestinal tract the oral bioavailability is only about 35% as a result of a high degree of first-pass metabolism . After injection into tissues, lidocaine is also rapidly absorbed and the absorption rate is affected by both vascularity and the presence of tissue and fat capable of binding lidocaine in the particular tissues .

The concentration of lidocaine in the blood is subsequently affected by a variety of aspects, including its rate of absorption from the site of injection, the rate of tissue distribution, and the rate of metabolism and excretion . Subsequently, the systemic absorption of lidocaine is determined by the site of injection, the dosage given, and its pharmacological profile . The maximum blood concentration occurs following intercostal nerve blockade followed in order of decreasing concentration, the lumbar epidural space, brachial plexus site, and subcutaneous tissue . The total dose injected regardless of the site is the primary determinant of the absorption rate and blood levels achieved . There is a linear relationship between the amount of lidocaine injected and the resultant peak anesthetic blood levels .

Nevertheless, it has been observed that lidocaine hydrochloride is completely absorbed following parenteral administration, its rate of absorption depending also on lipid solubility and the presence or absence of a vasoconstrictor agent . Except for intravascular administration, the highest blood levels are obtained following intercostal nerve block and the lowest after subcutaneous administration .

Additionally, lidocaine crosses the blood-brain and placental barriers, presumably by passive diffusion .

Approximately 12-20% of topically applied methyl salicylate may be systemically absorbed through intact skin within 10 hours of application, and absorption varies with different conditions such as surface area and pH. Dermal bioavailability is in the range of 11.8 – 30.7%. For the assessment of potential oral exposure to salicylates, bioavailability is assumed to be 100% .

Half Life

Following oral ingestion of equipotent dose of 26.6 mg of pure capsaicin, the half life was approximately 24.9 ± 5.0 min . Following topical application of 3% solution of capsaicin, the half-life of capsaicin was approximately 24 h . The mean population elimination half-life was 1.64 h following application of a topical patch containing 179 mg of capsaicin .

The elimination half-life of lidocaine hydrochloride following an intravenous bolus injection is typically 1.5 to 2.0 hours . Because of the rapid rate at which lidocaine hydrochloride is metabolized, any condition that affects liver function may alter lidocaine HCl kinetics . The half-life may be prolonged two-fold or more in patients with liver dysfunction .

The plasma half-life for salicylate is 2 to 3 hr in low doses and about 12 hr at usual anti-inflammatory doses. The half-life of salicylate may be as long as 15 to 30 hr at high therapeutic doses or when there is intoxication.

Clearance

The mean systemic clearance observed for intravenously administered lidocaine in a study of 15 adults was approximately 0.64 +/- 0.18 L/min .

Elimination Route

It is proposed that capsaicin mainly undergoes renal excretion, as both the unchanged and glucuronide form. A small fraction of unchanged compound is excreted in the feces and urine. In vivo animal studies demonstrates that less than 10 % of an administered dose was found in faces after 48 h .

The excretion of unchanged lidocaine and its metabolites occurs predominantly via the kidney with less than 5% in the unchanged form appearing in the urine . The renal clearance is inversely related to its protein binding affinity and the pH of the urine . This suggests by the latter that excretion of lidocaine occurs by non-ionic diffusion .

Excreted by kidneys as free salicylic acid (10%), salicyluric acid (75%), salicylic phenolic (10%) and acyl glucuronide (5%), and gentisic acid (less than 1%).

Pregnancy & Breastfeeding use

The safety of Capsaicin during pregnancy or lactation has not been established in either humans or animals.

Category B: Either animal-reproduction studies have not demonstrated a foetal risk but there are no controlled studies in pregnant women or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the 1st trimester (and there is no evidence of a risk in later trimesters).

Contraindication

Capsaicin cream is contraindicated on broken or irritated skin. It is also contraindicated in patients with known hypersensitivity to capsaicin or any of the excipients used in this product.

Hypovolaemia, complete heart block, Adam-Stokes syndrome, Wolff-Parkinson-White syndrome. Must not be applied to inflamed or injured skin.