TAMBALGIC

Indications

• Moderate to severe pain
• Postoperative pain
• Chronic pain management

Dosage

Children: For children aged 12-17 years, initially 50 mg, then adjusted according to response; usual maximum is 400 mg/24 hours.

Adults: Initially, 50-100 mg every 4-6 hours as needed. Maximum dose is 400 mg/24 hours.

Mechanism of action

Tramadol exerts its analgesic effects primarily through the modulation of pain pathways in the brain. It is a weak agonist of the mu-opioid receptor and also inhibits the reuptake of norepinephrine and serotonin, which contributes to its analgesic activity. This dual mechanism helps in managing pain by both blocking pain signals at the receptor level and enhancing descending inhibitory pathways.

Pharmacodynamics

Tramadol's pharmacodynamic properties are characterized by its ability to produce analgesia with a lower risk of respiratory depression compared to stronger opioids. It has a ceiling effect on respiratory depression, making it safer for use in non-opioid-tolerant patients. Common side effects include fatigue, dizziness, and gastrointestinal disturbances, while serious risks include seizures and serotonin syndrome, especially when combined with other serotonergic drugs.

Pharmacokinetics

Tramadol is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately 1-2 hours post-administration. It has a bioavailability of about 68% due to first-pass metabolism. The drug is extensively metabolized in the liver, primarily via cytochrome P450 enzymes, with a half-life of approximately 6-7 hours. It is excreted mainly in the urine, both as metabolites and unchanged drug.

Contra-indications

• Acute intoxication with alcohol
• Acute intoxication with analgesics
• Acute intoxication with hypnotics
• Acute intoxication with opioids
• Compromised respiratory function
• Uncontrolled epilepsy

Adverse effects

• Fatigue
• Postural hypotension
• Dyspnoea
• Epileptiform seizures
• Respiratory disorders
• Sleep disorders
• Blurred vision
• Asthma exacerbation
• Hypoglycaemia

Interactions

• Increased risk of respiratory depression with other CNS depressants
• May enhance the effects of alcohol
• Potential interaction with serotonergic drugs leading to serotonin syndrome

Precautions

• History of excessive bronchial secretions
• History of epilepsy-use only if compelling reasons exist
• Impaired consciousness
• Use with caution in patients susceptible to seizures
• Variation in metabolism may affect therapeutic effects

Pregnancy

Tramadol should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus. Use with caution.

Breast-feeding

Tramadol is excreted in breast milk. Caution should be exercised when administering to nursing mothers.

Storage

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

Formulations

• Tablets
• Oral solution
• Injectable forms (intravenous, intramuscular, subcutaneous)

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)

Indications

• Moderate to moderately severe pain
• Post-operative pain
• Chronic pain management

Dosage

Children: Refer to BNF for Children for specific pediatric dosing recommendations.

Adults: Refer to BNF for specific dosing information based on individual patient needs and clinical circumstances.

Mechanism of action

Tramadol acts primarily as a μ-opioid receptor agonist, binding with low affinity compared to morphine. It exists as a racemic mixture, with both enantiomers contributing to its analgesic effects: (+)-tramadol and its active metabolite (+)-O-desmethyl-tramadol (M1) act on the μ-opioid receptor while (+)-tramadol inhibits serotonin reuptake and (-)-tramadol inhibits norepinephrine reuptake. These actions work together to enhance pain modulation across multiple pathways.

Pharmacodynamics

Tramadol modulates the descending pain pathways in the central nervous system, resulting in analgesia. It can produce side effects similar to other opioids, such as dizziness, nausea, and constipation, but does not cause histamine release. It may also cause respiratory depression through its action on brain stem respiratory centers. Notably, tramadol can cause miosis, or constricted pupils, even in the absence of light.

Pharmacokinetics

Tramadol is absorbed rapidly after oral administration, reaching peak plasma concentrations within 1 to 2 hours. It is extensively metabolized in the liver, primarily via CYP2D6 and CYP3A4 enzymes, resulting in its active metabolite, M1. The elimination half-life ranges from 5 to 6 hours, and it is primarily excreted in the urine. The pharmacokinetics may vary due to genetic polymorphisms affecting metabolic enzymes.

Adverse effects

• dizziness
• somnolence
• nausea
• constipation
• sweating
• pruritus
• respiratory depression
• orthostatic hypotension
• miosis

Interactions

• carbamazepine+tramadol: Moderate (decreases concentration)
• bupropion+tramadol: Unknown (decreases efficacy)
• cinacalcet+tramadol: Unknown (decreases efficacy)
• terbinafine+tramadol: Unknown (decreases efficacy)

Pregnancy

Tramadol should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Tramadol is excreted in breast milk, and caution should be exercised when administering to nursing mothers.

Storage

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

Formulations

• tablets
• capsules
• injection
• oral solution

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.

Mechanism of action

Tramadol is a centrally acting μ-opioid receptor agonist and SNRI (serotonin/norepinephrine reuptake-inhibitor) that is structurally related to [codeine] and [morphine]. Tramadol binds weakly to κ- and δ-opioid receptors and to the μ-opioid receptor with 6000-fold less affinity than morphine. Tramadol exists as a racemic mixture consisting of two pharmacologically active enantiomers that both contribute to its analgesic property through different mechanisms: (+)-tramadol and its primary metabolite (+)-O-desmethyl-tramadol (M1) are agonists of the μ opioid receptor while (+)-tramadol inhibits serotonin reuptake and (-)-tramadol inhibits norepinephrine reuptake. These pathways are complementary and synergistic, improving tramadol's ability to modulate the perception of and response to pain. In animal models, M1 is up to 6 times more potent than tramadol in producing analgesia and 200 times more potent in μ-opioid binding. Tramadol has also been shown to affect a number of pain modulators including alpha2-adrenoreceptors, neurokinin 1 receptors, the voltage-gated sodium channel type II alpha subunit, transient receptor potential cation channel subfamily V member 1 (TRPV1 - also known as the capsaicin receptor), muscarinic receptors (M1 and M3), N-methyl-D-aspartate receptor (also known as the NMDA receptor or glutamate receptor), Adenosine A1 receptors, and nicotinic acetylcholine receptor. In addition to the above neuronal targets, tramadol has a number of effects on inflammatory and immune mediators involved in the pain response. This includes inhibitory effects on cytokines, prostaglandin E2 (PGE2), nuclear factor-κB, and glial cells as well as a change in the polarization state of M1 macrophages. Tramadol is a racemic mixture (R & S) that has a complicated mechanism of action. It has some mu-opioid receptor action, but this effect is 10 times lower than codeine and 6000 timex lower than morphine. Tramadol also inhibits the reuptake of norepinephrine (NE) and serotonin (5 HT) and produces secondary effects on alpha-2 adrenergic receptors in pain pathways. One isomer has greater effect on 5 HT reuptake and greater affinity for mu-opiate receptors. The other isomer is more potent for NE reuptake and less active for inhibiting 5 HT reuptake. Taken together, the effects of of tramadol may be explained through inhibition of 5 HT reuptake, action on alpha2 receptors, and mild activity on opiate mu-receptors. The transient receptor potential vanilloid 1 (TRPV1) and the transient receptor potential ankyrin 1 (TRPA1), which are expressed in sensory neurons, are polymodal nonselective cation channels that sense noxious stimuli. Recent reports showed that these channels play important roles in inflammatory, neuropathic, or cancer pain, suggesting that they may serve as attractive analgesic pharmacological targets. Tramadol is an effective analgesic that is widely used in clinical practice. Reportedly, tramadol and its metabolite (M1) bind to mu-opioid receptors and/or inhibit reuptake of monoamines in the central nervous system, resulting in the activation of the descending inhibitory system. However, the fundamental mechanisms of tramadol in pain control remain unclear. TRPV1 and TRPA1 may be targets of tramadol; however, they have not been studied extensively. We examined whether and how tramadol and M1 act on human embryonic kidney 293 (HEK293) cells expressing human TRPV1 (hTRPV1) or hTRPA1 by using a Ca imaging assay and whole-cell patch-clamp recording. Tramadol and M1 (0.01-10 uM) alone did not increase in intracellular Ca concentration ([Ca]i) in HEK293 cells expressing hTRPV1 or hTRPA1 compared with capsaicin (a TRPV1 agonist) or the allyl isothiocyanate (AITC, a TRPA1 agonist), respectively. Furthermore, in HEK293 cells expressing hTRPV1, pretreatment with tramadol or M1 for 5 minutes did not change the increase in [Ca]i induced by capsaicin. Conversely, pretreatment with tramadol (0.1-10 uM) and M1 (1-10 uM) significant

Pharmacodynamics

Tramadol modulates the descending pain pathways within the central nervous system through the binding of parent and M1 metabolite to μ-opioid receptors and the weak inhibition of the reuptake of norepinephrine and serotonin. Apart from analgesia, tramadol may produce a constellation of symptoms (including dizziness, somnolence, nausea, constipation, sweating and pruritus) similar to that of other opioids. **Central Nervous System** In contrast to [morphine], tramadol has not been shown to cause histamine release. At therapeutic doses, tramadol has no effect on heart rate, left-ventricular function or cardiac index. Orthostatic hypotension has been observed. Tramadol produces respiratory depression by direct action on brain stem respiratory centres. The respiratory depression involves both a reduction in the responsiveness of the brain stem centres to increases in CO2 tension and to electrical stimulation. Tramadol depresses the cough reflex by a direct effect on the cough centre in the medulla. Antitussive effects may occur with doses lower than those usually required for analgesia. Tramadol causes miosis, even in total darkness. Pinpoint pupils are a sign of opioid overdose but are not pathognomonic (e.g., pontine lesions of hemorrhagic or ischemic origin may produce similar findings). Marked mydriasis rather than miosis may be seen with hypoxia in the setting of oxycodone overdose. Seizures have been reported in patients receiving tramadol within the recommended dosage range. Spontaneous post-marketing reports indicate that seizure risk is increased with doses of tramadol above the recommended range. Risk of convulsions may also increase in patients with epilepsy, those with a history of seizures or in patients with a recognized risk for seizure (such as head trauma, metabolic disorders, alcohol and drug withdrawal, CNS infections), or with concomitant use of other drugs known to reduce the seizure threshold. Tramadol can cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs (e.g., anti-depressants, migraine medications). Treatment with the serotoninergic drug should be discontinued if such events (characterized by clusters of symptoms such as hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs, mental status changes including confusion, irritability, extreme agitation progressing to delirium and coma) occur and supportive symptomatic treatment should be initiated. Tramadol should not be used in combination with MAO inhibitors or serotonin-precursors (such as L-tryptophan, oxitriptan) and should be used with caution in combination with other serotonergic drugs (triptans, certain tricyclic antidepressants, lithium, St. John’s Wort) due to the risk of serotonin syndrome. **Gastrointestinal Tract and Other Smooth Muscle** Tramadol causes a reduction in motility associated with an increase in smooth muscle tone in the antrum of the stomach and duodenum. Digestion of food in the small intestine is delayed and propulsive contractions are decreased. Propulsive peristaltic waves in the colon are decreased, while tone may be increased to the point of spasm resulting in constipation. Other opioid-induced effects may include a reduction in gastric, biliary and pancreatic secretions, spasm of the sphincter of Oddi, and transient elevations in serum amylase. **Endocrine System** Opioids may influence the hypothalamic-pituitary-adrenal or -gonadal axes. Some changes that can be seen include an increase in serum prolactin and decreases in plasma cortisol and testosterone. Clinical signs and symptoms may be manifest from these hormonal changes. Hyponatremia has been reported very rarely with the use of tramadol, usually in patients with predisposing risk factors, such as elderly patients and/or patients using concomitant medications that may cause hyponatremia (e.g., antidepressants, benzodiazepines, diureti