Panadol Extra (Acetaminophen,Caffeine)

Uses

Acetaminophen is an analgesic drug used alone or in combination with opioids for pain management, and as an antipyretic agent.

In general, acetaminophen is used for the treatment of mild to moderate pain and reduction of fever. It is available over the counter in various forms, the most common being oral forms.

Acetaminophen injection is indicated for the management of mild to moderate pain, the management of moderate to severe pain with adjunctive opioid analgesics, and the reduction of fever.

Because of its low risk of causing allergic reactions, this drug can be administered in patients who are intolerant to salicylates and those with allergic tendencies, including bronchial asthmatics. Specific dosing guidelines should be followed when administering acetaminophen to children.

Caffeine is a stimulant present in tea, coffee, cola beverages, analgesic drugs, and agents used to increase alertness. It is also used in to prevent and treat pulmonary complications of premature birth.

Caffeine is indicated for the short term treatment of apnea of prematurity in infants and off label for the prevention and treatment of bronchopulmonary dysplasia caused by premature birth. In addition, it is indicated in combination with sodium benzoate to treat respiratory depression resulting from an overdose with CNS depressant drugs. Caffeine has a broad range of over the counter uses, and is found in energy supplements, athletic enhancement products, pain relief products, as well as cosmetic products.

Panadol Extra (Acetaminophen,Caffeine) is also used to associated treatment for these conditions: Acute Gouty Arthritis, Acute Musculoskeletal Pain, Allergies, Ankylosing Spondylitis (AS), Arthritis, Chills, Cold, Cold Symptoms, Common Cold, Common Cold/Flu, Cough, Cough caused by Common Cold, Coughing caused by Flu caused by Influenza, Dyskinesia of the Biliary Tract, Dyskinesia of the Urinary Tract, Febrile Convulsions, Febrile Illness Acute, Fever, Fibromyalgia Syndrome, Flu caused by Influenza, Headache, Joint dislocations, Menstrual Distress (Dysmenorrhea), Mild pain, Muscle Inflammation, Muscle Injuries, Muscle Spasms, Musculoskeletal Pain, Nasal Congestion, Neuralgia, Osteoarthritis (OA), Pain, Pollen Allergy, Postoperative pain, Premenstrual cramps, Rheumatoid Arthritis, Rhinopharyngitis, Rhinorrhoea, Severe Pain, Sinusitis, Soreness, Muscle, Spasms, Spastic Pain of the Gastrointestinal Tract, Sprains, Tension Headache, Toothache, Upper Respiratory Tract Infection, Whiplash Syndrome, Acute Torticollis, Mild to moderate pain, Minor aches and pains, Minor pain, Moderate Pain, Airway secretion clearance therapy, Antispasmodic, BronchodilationBronchopulmonary Dysplasia (BPD), Common Cold, Dark circles under eyes, Dyspepsia, Fatigue, Fever, Flu caused by Influenza, Headache, Migraine, Pain, Pain, Acute, Pain, Menstrual, Primary apnea of premature newborns, Respiratory Depression, Rheumatic Pain, Somnolence, Soreness, Muscle, Tension Headache, Toothache, Moderate Pain, Analgesia, Antacid therapy, Athletic Performance

How Panadol Extra (Acetaminophen,Caffeine) works

According to its FDA labeling, acetaminophen's exact mechanism of action has not been fully established - despite this, it is often categorized alongside NSAIDs (nonsteroidal anti-inflammatory drugs) due to its ability to inhibit the cyclooxygenase (COX) pathways. It is thought to exert central actions which ultimately lead to the alleviation of pain symptoms.

One theory is that acetaminophen increases the pain threshold by inhibiting two isoforms of cyclooxygenase, COX-1 and COX-2, which are involved in prostaglandin (PG) synthesis. Prostaglandins are responsible for eliciting pain sensations. Acetaminophen does not inhibit cyclooxygenase in peripheral tissues and, therefore, has no peripheral anti-inflammatory effects. Though acetylsalicylic acid (aspirin) is an irreversible inhibitor of COX and directly blocks the active site of this enzyme, studies have shown that acetaminophen (paracetamol) blocks COX indirectly. Studies also suggest that acetaminophen selectively blocks a variant type of the COX enzyme that is unique from the known variants COX-1 and COX-2. This enzyme has been referred to as COX-3. The antipyretic actions of acetaminophen are likely attributed to direct action on heat-regulating centers in the brain, resulting in peripheral vasodilation, sweating, and loss of body heat. The exact mechanism of action of this drug is not fully understood at this time, but future research may contribute to deeper knowledge.

The mechanism of action of caffeine is complex, as it impacts several body systems, which are listed below. The effects as they relate to various body systems are described as follows:

General and cellular actions

Caffeine exerts several actions on cells, but the clinical relevance is poorly understood. One probable mechanism is the inhibition of nucleotide phosphodiesterase enzymes, adenosine receptors, regulation of calcium handling in cells, and participates in adenosine receptor antagonism. Phosphodiesterase enzymes regulate cell function via actions on second messengers cAMP and cGMP. This causes lipolysis through activation of hormone-sensitive lipases, releasing fatty acids and glycerol.

Respiratory

The exact mechanism of action of caffeine in treating apnea related to prematurity is unknown, however, there are several proposed mechanisms, including respiratory center stimulation in the central nervous system, a reduced threshold to hypercapnia with increased response, and increased consumption of oxygen, among others. The blocking of the adenosine receptors enhances respiratory drive via an increase in brain medullary response to carbon dioxide, stimulating ventilation and respiratory drive, while increasing contractility of the diaphragm.

Central nervous system

Caffeine demonstrates antagonism of all 4 adenosine receptor subtypes (A1, A2a, A2b, A3) in the central nervous system. Caffeine's effects on alertness and combatting drowsiness are specifically related to the antagonism of the A2a receptor.

Renal system

Caffeine has diuretic effects due to is stimulatory effects on renal blood flow, increase in glomerular filtration, and increase in sodium excretion.

Cardiovascular system

Adenosine receptor antagonism at the A1 receptor by caffeine stimulates inotropic effects in the heart. Blocking of adenosine receptors promotes catecholamine release, leading to stimulatory effects occurring in the heart and the rest of the body. In the blood vessels, caffeine exerts direct antagonism of adenosine receptors, causing vasodilation. It stimulates the endothelial cells in the blood vessel wall to release nitric oxide, potentiating blood vessel relaxation. Catecholamine release, however, antagonizes this and exerts inotropic and chronotropic effects on the heart, ultimately leading to vasoconstriction. Finally, caffeine is shown to raise systolic blood pressure measurements by 5 to 10 mmHg when it is not taken regularly, versus no effect in those who consume it regularly. The vasoconstricting effects of caffeine are beneficial in migraines and other types of headache, which are normally caused by vasodilation in the brain.

Toxicity

LD50 = 338 mg/kg (oral, mouse); LD50 = 1944 mg/kg (oral, rat)

Overdose and liver toxicity

Acetaminophen overdose may be manifested by renal tubular necrosis, hypoglycemic coma, and thrombocytopenia. Sometimes, liver necrosis can occur as well as liver failure. Death and the requirement of a liver transplant may also occur. Metabolism by the CYP2E1 pathway releases a toxic acetaminophen metabolite known as N-acetyl-p-benzoquinoneimine(NAPQI). The toxic effects caused by this drug are attributed to NAPQI, not acetaminophen alone.

Carcinogenesis

Long-term studies in mice and rats have been completed by the National Toxicology Program to study the carcinogenic risk of acetaminophen. In 2-year feeding studies, F344/N rats and B6C3F1 mice consumed a diet containing acetaminophen up to 6,000 ppm. Female rats showed evidence of carcinogenic activity demonstrated by a higher incidence of mononuclear cell leukemia at doses 0.8 times the maximum human daily dose (MHDD). No evidence of carcinogenesis in male rats (0.7 times) or mice (1.2 to 1.4 times the MHDD) was noted. The clinical relevance of this finding in humans is unknown.

Mutagenesis

Acetaminophen was not found to be mutagenic in the bacterial reverse mutation assay (Ames test). Despite this finding, acetaminophen tested positive in the in vitro mouse lymphoma assay as well as the in vitro chromosomal aberration assay using human lymphocytes. In published studies, acetaminophen has been reported to be clastogenic (disrupting chromosomes) when given a high dose of 1,500 mg/kg/day to the rat model (3.6 times the MHDD). No clastogenicity was observed at a dose of 750 mg/kg/day (1.8 times the MHDD), indicating that this drug has a threshold before it may cause mutagenesis. The clinical relevance of this finding in humans is unknown.

Impairment of Fertility

In studies conducted by the National Toxicology Program, fertility assessments have been performed in Swiss mice in a continuous breeding study. No effects on fertility were seen.

Use in pregnancy and nursing

The FDA label for acetaminophen considers it a pregnancy category C drug, meaning this drug has demonstrated adverse effects in animal studies. No human clinical studies in pregnancy have been done to this date for intravenous acetaminophen. Use acetaminophen only when necessary during pregnancy. Epidemiological data on oral acetaminophen use in pregnant women demonstrate no increase in the risk of major congenital malformations. While prospective clinical studies examining the results of nursing with acetaminophen use have not been conducted, acetaminophen is found secreted in human milk at low concentrations after oral administration. Data from more than 15 nursing mothers taking acetaminophen was obtained, and the calculated daily dose of acetaminophen that reaches the infant is about 1 to 2% of the maternal dose. Caution should be observed when acetaminophen is taken by a nursing woman.

The oral LD50 of caffeine in rats is 192 mg/kg. An acute fatal overdose of caffeine in humans is about 10–14 grams (equivalent to 150–200 mg/kg of body weight).

Caffeine overdose

In the case of caffeine overdose, seizures may occur, as caffeine is a central nervous system stimulant. It should be used with extreme caution in those with epilepsy or other seizure disorders. Symptoms of overdose may include nausea, vomiting, diarrhea, and gastrointestinal upset. Intoxication with caffeine is included in the World Health Organization’s International Classification of Diseases (ICD-10). Agitation, anxiety, restlessness, insomnia, tachycardia, tremors, tachycardia, psychomotor agitation, and, in some cases, death can occur, depending on the amount of caffeine consumed. Overdose is more likely to occur in individuals who do not consume caffeine regularly but consume energy drinks.

Overdose management

For a mild caffeine overdose, offer symptomatic treatment. In the case of a severe overdose, intubation for airway protection from changes in mental status or vomiting may be needed. Activated charcoal and hemodialysis can prevent further complications of an overdose and prevent absorption and metabolism. Benzodiazepine drugs can be administered to prevent or treat seizures. IV fluids and vasopressors may be necessary to combat hypotension associated with caffeine overdose. In addition, magnesium and beta blocking drugs can be used to treat arrhythmias that may occur, with defibrillation and resuscitation if the arrhythmias are lethal. Follow local ACLS protocols.

Volume of Distribution

Volume of distribution is about 0.9L/kg. 10 to 20% of the drug is bound to red blood cells. Acetaminophen appears to be widely distributed throughout most body tissues except in fat.

Caffeine has the ability to rapidly cross the blood-brain barrier. It is water and fat soluble and distributes throughout the body. Caffeine concentrations in the cerebrospinal fluid of preterm newborns are similar to the concentrations found in the plasma. The mean volume of distribution of caffeine in infants is 0.8-0.9 L/kg and 0.6 L/kg in the adult population.

Elimination Route

Acetaminophen has 88% oral bioavailability and reaches its highest plasma concentration 90 minutes after ingestion. Peak blood levels of free acetaminophen are not reached until 3 hours after rectal administration of the suppository form of acetaminophen and the peak blood concentration is approximately 50% of the observed concentration after the ingestion of an equivalent oral dose (10-20 mcg/mL).

The percentage of a systemically absorbed rectal dose of acetaminophen is inconsistent, demonstrated by major differences in the bioavailability of acetaminophen after a dose administered rectally. Higher rectal doses or an increased frequency of administration may be used to attain blood concentrations of acetaminophen similar to those attained after oral acetaminophen administration.

Caffeine is rapidly absorbed after oral or parenteral administration, reaching peak plasma concentration within 30 minutes to 2 hours after administration. After oral administration, onset of action takes place within 45 to 1 hour. Food may delay caffeine absorption. The peak plasma level for caffeine ranges from 6-10mg/L. The absolute bioavailability is unavailable in neonates, but reaches about 100% in adults.

Half Life

The half-life for adults is 2.5 h after an intravenous dose of 15 mg/kg. After an overdose, the half-life can range from 4 to 8 hours depending on the severity of injury to the liver, as it heavily metabolizes acetaminophen.

In an average-sized adult or child above the age of 9, the half-life of caffeine is approximately 5 hours. Various characteristics and conditions can alter caffeine half-life. It can be reduced by up to 50% in smokers. Pregnant women show an increased half-life of 15 hours or higher, especially in the third trimester. The half-life in newborns is prolonged to about 8 hours at full-term and 100 hours in premature infants, likely due to reduced ability to metabolize it. Liver disease or drugs that inhibit CYP1A2 can increase caffeine half-life.

Clearance

Adults: 0.27 L/h/kg following a 15 mg/kg intravenous (IV) dose. Children: 0.34 L/h/kg following a 15 mg/kg intravenous (IV dose).

The clearance of caffeine varies, but on average, is about 0.078 L/kg/h (1.3 mL/min/kg).

Elimination Route

Acetaminophen metabolites are mainly excreted in the urine. Less than 5% is excreted in the urine as free (unconjugated) acetaminophen and at least 90% of the administered dose is excreted within 24 hours.

The major metabolites of caffeine can be found excreted in the urine. About 0.5% to 2% of a caffeine dose is found excreted in urine, as it because it is heavily absorbed in the renal tubules.

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