NEWCOX P

Indications

• Osteoarthritis
• Rheumatoid arthritis
• Ankylosing spondylitis
• Acute pain
• Gout

Dosage

Children: Refer to the BNF for Children for appropriate paediatric dosing

Adults: Refer to the BNF for specific dosing recommendations based on the condition being treated.

Mechanism of action

Etoricoxib exerts its effects by selectively inhibiting the enzyme cyclooxygenase-2 (COX-2), which is involved in the conversion of arachidonic acid to prostaglandins. This selective inhibition decreases the levels of prostaglandins in inflamed tissues, leading to reduced pain, swelling, and inflammation. Unlike non-selective NSAIDs, etoricoxib does not significantly inhibit COX-1, thus sparing gastric mucosa and minimizing gastrointestinal side effects.

Pharmacodynamics

The pharmacodynamic effects of etoricoxib include pain relief and anti-inflammatory effects through the inhibition of COX-2. This leads to decreased synthesis of prostaglandins, which play a key role in mediating pain and inflammation. The onset of analgesic effects typically occurs within hours of administration, with peak effects reached between 6 to 12 hours after dosing.

Pharmacokinetics

Etoricoxib is well absorbed following oral administration, with peak plasma concentrations occurring within 1 to 2 hours. It has a high bioavailability of approximately 100% and is extensively metabolized in the liver through cytochrome P450 enzymes, primarily CYP2C9. The elimination half-life averages about 22 hours, allowing for once-daily dosing. It is primarily excreted in urine as metabolites, with less than 1% of the drug excreted unchanged.

Contra-indications

• Severe allergic reactions to etorixocib or any excipients
• Active peptic ulcer disease
• History of gastrointestinal bleeding or perforation related to NSAIDs
• Severe hepatic impairment
• Severe renal impairment
• Heart failure
• Pregnancy

Adverse effects

• Hypertension
• Gastrointestinal disturbances (e.g., nausea, vomiting, diarrhea, abdominal pain)
• Renal impairment
• Hepatotoxicity
• Skin reactions (e.g., rash, urticaria)
• Cardiovascular events (e.g., myocardial infarction, stroke)
• Dizziness
• Headache

Interactions

• Anticoagulants (e.g., warfarin) - increased risk of bleeding
• Other NSAIDs - increased risk of gastrointestinal adverse effects
• Diuretics - may reduce the effectiveness
• ACE inhibitors - may reduce the effectiveness
• Lithium - may increase lithium levels

Precautions

• Monitor blood pressure regularly in long-term use
• Use with caution in patients with a history of cardiovascular disease
• Assess renal function prior to initiation and periodically during treatment
• Avoid concurrent use with other NSAIDs
• Consider gastrointestinal prophylaxis in high-risk patients

Pregnancy

Etoricoxib is not recommended during pregnancy due to potential risks to the fetus, particularly in the third trimester.

Breast-feeding

Etoricoxib is excreted in breast milk; caution is advised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Tablets (60 mg, 90 mg, 120 mg)

Indications

• Mild to moderate pain
• Fever
• Headaches
• Muscle aches
• Arthritis
• Backaches
• Toothaches
• Colds

Dosage

Adults: For adults, the typical dosage is 500 mg to 1 g every 4 to 6 hours, with a maximum daily limit of 4 g. In cases of intravenous administration, the dosage is 15 mg/kg every

Mechanism of action

Paracetamol is thought to exert its analgesic effects by inhibiting cyclo-oxygenase (COX) enzymes, specifically COX-1 and COX-2, which are involved in the synthesis of prostaglandins responsible for pain sensation. Unlike most NSAIDs, paracetamol does not exhibit peripheral anti-inflammatory effects. Its antipyretic action is believed to result from direct action on heat-regulating centers in the brain, leading to peripheral vasodilation and sweating.

Pharmacodynamics

Paracetamol has been shown to have both antipyretic and analgesic effects, lacking any significant anti-inflammatory activity. It does not interfere with platelet aggregation or disrupt hemostasis, making it a safer option for individuals at risk of bleeding. Allergic reactions to paracetamol are rare. The drug does not affect uric acid secretion or acid-base balance when used at recommended doses.

Pharmacokinetics

Paracetamol is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations typically occurring within 30 to 60 minutes after oral administration. It is primarily metabolized in the liver via conjugation with glucuronide and sulfate, with a minor pathway involving cytochrome P450 enzymes. The elimination half-life ranges from 1 to 4 hours, with renal excretion of metabolites as the primary route of elimination.

Adverse effects

• Nausea and vomiting
• Liver injury
• Renal damage
• Hypersensitivity reactions
• Flushing
• Hypotension
• Anorectal erythema
• Angioedema
• Agranulocytosis
• Thrombocytopenia
• Leukopenia
• Severe cutaneous adverse reactions (SCARs)

Interactions

• Increased risk of methaemoglobinaemia with topical prilocaine
• Increased risk of methaemoglobinaemia with topical anaesthetics
• Increased anticoagulant effect with coumarins
• Increased risk of hepatotoxicity with imatinib
• Decreased exposure with rifampicin
• Decreased exposure with pitolisant

Precautions

• Monitor patients with liver disease or heavy alcohol use for increased risk of hepatotoxicity
• Adjust doses in patients taking enzyme-inducing antiepileptic medications
• Use caution in patients with renal impairment
• Clinical judgement is required for dose adjustment in weight-based dosing

Pregnancy

Paracetamol is generally considered safe to use during pregnancy for pain and fever relief, but should be used at the lowest effective dose for the shortest duration necessary.

Breast-feeding

Paracetamol is excreted in breast milk in small amounts and is considered safe for use while breastfeeding.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Oral tablets (500 mg)
• Oral suspension (120 mg/5 mL, 500 mg/5 mL)
• Rectal suppositories (various strengths)
• Intravenous infusion (various strengths)

Mechanism of action

According to its FDA labeling, acetaminophen's exact mechanism of action has not been fully established - despite this, it is often categorized alongside NSAIDs (non-steroidal anti-inflammatory drugs) due to its ability to inhibit the cyclo-oxygenase (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 cyclo-oxygenase, 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. Although further investigation is warranted, the active metabolite of acetaminophen (AM404) was shown to interact with several molecular targets, including the Ca_v3.2 calcium channel, the cannabinoid CB1 receptors, TRPV1 receptors, and Na_v1.8 and Na_v1.7 channels. Acetaminophen produces analgesia and antipyresis by a mechanism similar to that of salicylates. Unlike salicylates, however, acetaminophen does not have uricosuric activity. There is some evidence that acetaminophen has weak anti-inflammatory activity in some nonrheumatoid conditions (e.g., in patients who have had oral surgery). ... Acetaminophen lowers body temperature in patients with fever but rarely lowers normal body temperature. The drug acts on the hypothalamus to produce antipyresis; heat dissipation is increased as a result of vasodilation and increased peripheral blood flow. The effects of acetaminophen on cyclooxygenase activity have not been fully determined. Acetaminophen is a weak, reversible, isoform-nonspecific cyclooxygenase inhibitor at dosages of 1 g daily. The inhibitory effect of acetaminophen on cyclooxygenase-1 is limited, and the drug does not inhibit platelet function. Therapeutic doses of acetaminophen appear to have little effect on cardiovascular and respiratory systems; however, toxic doses may cause circulatory failure and rapid, shallow breathing. Acetaminophen (N-acetyl-p-aminophenol (APAP)) is the most common antipyretic/analgesic medicine worldwide. If APAP is overdosed, its metabolite, N-acetyl-p-benzo-quinoneimine (NAPQI), causes liver damage. However, epidemiological evidence has associated previous use of therapeutic APAP doses with the risk of chronic obstructive pulmonary disease (COPD) and asthma. The transient receptor potential ankyrin-1 (TRPA1) channel is expressed by peptidergic primary sensory neurons. Because NAPQI, like other TRPA1 activators, is an electrophilic molecule, /the researchers/ hypothesized that APAP, via NAPQI, stimulates TRPA1, thus causing airway neurogenic inflammation. NAPQI selectively excites human recombinant and native (neuroblastoma cells) TRPA1. TRPA1 activation by NAPQI releases proinflammatory neuropeptides (substance P and calcitonin gene-related peptide) from sensory nerve terminals in rodent airways, thereby causing neurogenic edema and neutrophilia. Single or repeated administration of therapeutic (15-60 mg/kg) APAP doses to mice produces detectable levels of NAPQI in the lung, and increases neutrophil numbers, myeloperoxidase

Pharmacodynamics

Animal and clinical studies have determined that acetaminophen has both antipyretic and analgesic effects. This drug has been shown to lack anti-inflammatory effects. As opposed to the _salicylate_ drug class, acetaminophen does not disrupt tubular secretion of uric acid and does not affect acid-base balance if taken at the recommended doses. Acetaminophen does not disrupt hemostasis and does not have inhibitory activities against platelet aggregation. Allergic reactions are rare occurrences following acetaminophen use.