COLDRID TABLETS

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

• Management of fatigue and drowsiness
• Enhancement of cognitive performance
• Support in the treatment of headaches, particularly tension-type headaches

Dosage

Children: Refer to BNF for Children for appropriate dosing.

Adults: Refer to specific clinical guidelines or BNF for appropriate dosing.

Mechanism of action

Caffeine primarily acts as an adenosine receptor antagonist. By blocking adenosine receptors, particularly A1 and A2A receptors, caffeine promotes neuronal firing and increases the release of neurotransmitters such as dopamine and norepinephrine. This leads to enhanced alertness, improved mood, and increased mental performance. Additionally, caffeine increases cyclic AMP levels by inhibiting phosphodiesterase, further contributing to its stimulant effects.

Pharmacodynamics

The pharmacodynamic effects of caffeine include increased heart rate, enhanced respiratory drive, improved cognitive function, and increased physical performance. It can also induce diuresis and stimulate gastric acid secretion. The effects of caffeine can vary based on individual tolerance, genetic factors, and the presence of other conditions.

Pharmacokinetics

Caffeine is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations typically occurring within 30 to 120 minutes after ingestion. It is widely distributed throughout the body, crossing the blood-brain barrier and placenta. The half-life of caffeine varies significantly among individuals, ranging from about 3 to 7 hours, influenced by factors such as age, liver function, pregnancy, and genetic polymorphisms. It is primarily metabolized in the liver by cytochrome P450 enzymes, particularly CYP1A2, into three primary metabolites: paraxanthine, theobromine, and theophylline, which also exhibit pharmacological activity.

Contra-indications

• Hypersensitivity to caffeine or any of its components
• Severe anxiety disorders
• Cardiac arrhythmias
• Peptic ulcer disease
• Uncontrolled hypertension

Adverse effects

• Insomnia
• Nervousness
• Restlessness
• Stomach irritation
• Nausea
• Vomiting
• Tachycardia
• Headache
• Dizziness
• Increased heart rate

Interactions

• May enhance the effects of other stimulants
• Theophylline levels may increase with caffeine
• Caffeine may reduce the sedative effects of benzodiazepines
• Caffeine can alter the metabolism of certain medications such as warfarin and lithium

Precautions

• Use with caution in patients with cardiovascular disease
• Consider potential for dependence with chronic use
• Monitor for anxiety exacerbation in predisposed individuals
• Assess for interactions with other medications

Pregnancy

Caffeine consumption is generally advised to be limited during pregnancy due to potential risks of miscarriage and low birth weight. Consultation with a healthcare provider is recommended.

Breast-feeding

Caffeine is excreted in breast milk, and while moderate consumption is considered safe, excessive intake should be avoided. Monitoring for potential effects on the infant is advised.

Storage

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

Formulations

• Caffeine tablets
• Caffeine capsules
• Caffeine liquid solutions
• Caffeinated beverages

Indications

• Allergic rhinitis (hay fever)
• Urticaria (hives)
• Allergic conjunctivitis
• Common cold symptoms

Dosage

Children: For children aged 6-12 years, the dose is typically 2 mg every 4 to 6 hours, not exceeding 12 mg per day. For children under

Adults: The usual adult dose for chlorpheniramine is 4 mg every 4 to 6 hours, not to exceed 24 mg per day.

Mechanism of action

Chlorpheniramine binds to the histamine H1 receptor, preventing endogenous histamine from exerting its effects. This leads to temporary relief from symptoms such as sneezing, pruritus, and increased vascular permeability associated with allergic reactions. The drug competes with histamine for H1-receptor sites on effector cells, thus antagonizing most of the pharmacological effects of histamine, including its actions on smooth muscle and vascular permeability.

Pharmacodynamics

In allergic reactions, allergens trigger the degranulation of mast cells and basophils, leading to the release of histamine. Chlorpheniramine, as an H1 antagonist, competes for receptor binding, effectively blocking histamine-induced effects, such as itching, vasodilation, and bronchoconstriction. This results in relief from symptoms like sneezing, watery eyes, and nasal discharge.

Pharmacokinetics

Chlorpheniramine is well absorbed from the gastrointestinal tract. It undergoes hepatic metabolism and its effects can last for several hours. The onset of action is typically observed within 1 to 2 hours following oral administration, with peak effects occurring around 2 to 6 hours. The drug is eliminated primarily through urine, with a half-life ranging from 12 to 15 hours, though this can vary based on individual factors.

Contra-indications

• Hypersensitivity to chlorpheniramine or any component of the formulation
• Acute asthma attacks
• Severe hypertension
• Narrow-angle glaucoma
• Prostatic hypertrophy

Adverse effects

• Drowsiness
• Dizziness
• Dry mouth
• Blurred vision
• Constipation
• Urinary retention
• Confusion
• Headache

Interactions

• Alcohol
• CNS depressants
• MAO inhibitors
• Anticholinergic agents
• Beta-blockers

Precautions

• Use with caution in patients with cardiovascular disease
• Caution in patients with liver or kidney impairment
• Avoid in elderly patients due to increased risk of sedation and anticholinergic effects
• May impair the ability to drive or operate machinery

Pregnancy

Chlorpheniramine should be used in pregnancy only if clearly needed. Consult medical professionals for guidance.

Breast-feeding

Chlorpheniramine 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
• Syrup
• Oral suspension

Indications

• Insomnia
• Sleep disturbances
• Anxiety-related sleep issues
• Jet lag

Dosage

Children: Refer to specific medication prescribing information for paediatric doses, as this also varies widely among sleep aids.

Adults: Refer to specific medication prescribing information for adult doses, as this varies widely among sleep aids.

Mechanism of action

Many sleep medications, such as benzodiazepines and non-benzodiazepine sleep aids, work by enhancing the effects of gamma-aminobutyric acid (GABA), a neurotransmitter that inhibits neuronal activity. This results in increased sedation and reduced time to sleep onset. Other agents, such as melatonin receptor agonists, mimic the action of melatonin, a hormone that regulates sleep-wake cycles.

Pharmacodynamics

The pharmacodynamics of sleep aids generally involve the modulation of neurotransmitters involved in sleep regulation. For example, benzodiazepines act on GABA-A receptors to increase GABAergic activity, leading to sedation, anxiolysis, and muscle relaxation. Non-benzodiazepine agents may selectively target specific GABA receptor subtypes to minimize side effects while promoting sleep. Melatonin receptor agonists, on the other hand, help to synchronize circadian rhythms and promote sleep onset.

Pharmacokinetics

The pharmacokinetics of sleep medications vary depending on the specific agent. Generally, these drugs are absorbed rapidly, with peak plasma concentrations occurring within one to several hours post-administration. The elimination half-life can range from a few hours to over 24 hours, influencing the duration of action and potential for next-day sedation. Metabolism often occurs in the liver via cytochrome P450 enzymes, and renal excretion is the primary route of elimination for many sleep aids.

Pregnancy

Safety during pregnancy has not been established. Consultation with a healthcare provider is recommended.

Breast-feeding

Limited data available; consult a healthcare provider for recommendations.

Storage

Store in a cool, dry place away from direct sunlight.

Indications

• Nasal congestion
• Hypotension during anesthesia
• Vasoconstriction in certain surgical procedures
• Pupil dilation in ocular procedures

Dosage

Children: Refer to the BNF for Children for appropriate dosing in pediatric patients.

Adults: Refer to the relevant clinical guidelines and product information for specific dosing recommendations.

Mechanism of action

Phenylephrine exerts its effects by selectively activating alpha-1 adrenergic receptors on vascular smooth muscle. This activation leads to vasoconstriction, which increases systemic vascular resistance and, consequently, blood pressure. In the nasal mucosa, vasoconstriction reduces blood flow and edema, alleviating congestion.

Pharmacodynamics

The pharmacodynamic effects of phenylephrine include increased peripheral vascular resistance and decreased nasal mucosal edema. The drug's onset of action is typically rapid, with peak effects occurring within 30 minutes when administered intranasally or intravenously. The duration of action can vary depending on the route of administration but is generally between 1 to 4 hours.

Pharmacokinetics

Phenylephrine is well absorbed when administered orally, but it undergoes significant first-pass metabolism, which reduces its bioavailability. When administered intranasally or intravenously, it avoids this first-pass effect, leading to more pronounced effects. The drug is metabolized primarily in the liver via conjugation and has a half-life of approximately 2 to 3 hours. Renal excretion is the primary route for elimination.

Contra-indications

• Severe hypertension
• Severe coronary artery disease
• Narrow-angle glaucoma
• Hypersensitivity to phenylephrine or any component of the formulation

Adverse effects

• Hypertension
• Reflex bradycardia
• Headache
• Nausea
• Restlessness
• Insomnia
• Dizziness
• Dry mouth

Interactions

• MAO inhibitors may increase the hypertensive effect
• Tricyclic antidepressants may enhance the effects of phenylephrine
• Beta-blockers may counteract the effects of phenylephrine
• Other sympathomimetics may have additive effects

Precautions

• Use with caution in patients with cardiovascular disease
• Caution in patients with hyperthyroidism
• Monitor blood pressure during use
• Not recommended for use in patients taking antihypertensive medications

Pregnancy

Phenylephrine is classified as category C; caution is advised as there are no well-controlled studies in pregnant women.

Breast-feeding

Phenylephrine is excreted in breast milk; caution is advised due to the potential effects on the infant.

Storage

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

Formulations

• Tablets
• Oral liquid
• Nasal spray
• Injectable solution

Mechanism of action

Chlorpheniramine binds to the histamine H1 receptor. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine. Antihistamines used in the treatment of allergy act by competing with histamine for H1-receptor sites on effector cells. They thereby prevent, but do not reverse, responses mediated by histamine alone. Antihistamines antagonize, in varying degrees, most of the pharmacological effects of histamine, including urticaria and pruritus. Also, the anticholinergic actions of most antihistamines provide a drying effect on the nasal mucosa. /Antihistamines/ H1 antagonists inhibit most responses of smooth muscle to histamine. Antagonism of the constrictor action of histamine on respiratory smooth muscle is easily shown in vivo and in vitro. /Histamine Antagonists: H1 Antagonists/ H1 antagonists strongly block the action of histamine that results in increased permeability and formation of edema and wheal. /Histamine Antagonists: H1 Antagonists/ Within the vascular tree, the H1 antagonists inhibit both the vasoconstrictor effects of histamine and, to a degree, the more rapid vasodilator effects that are mediated by H1 receptors on endothelial cells. Residual vasodilatation reflects the involvement of H2 receptors on smooth muscle and can be suppressed only by the concurrent administration of an H2 antagonist. Effects of the histamine antagonists on histamine induced changes in systemic blood pressure parallel these vascular effects. /Histamine Antagonists: H1 Antagonists/ Many of the H1 antagonists tend to inhibit responses to acetylcholine that are mediated by muscarinic receptors. These atropine like actions are sufficiently prominent in some of the drugs to be manifest during clinical usage ... . /Histamine Antagonists: H1 Antagonists/

Pharmacodynamics

In allergic reactions an allergen interacts with and cross-links surface IgE antibodies on mast cells and basophils. Once the mast cell-antibody-antigen complex is formed, a complex series of events occurs that eventually leads to cell-degranulation and the release of histamine (and other chemical mediators) from the mast cell or basophil. Once released, histamine can react with local or widespread tissues through histamine receptors. Histamine, acting on H₁-receptors, produces pruritis, vasodilatation, hypotension, flushing, headache, tachycardia, and bronchoconstriction. Histamine also increases vascular permeability and potentiates pain. Chlorpheniramine, is a histamine H1 antagonist (or more correctly, an inverse histamine agonist) of the alkylamine class. It competes with histamine for the normal H₁-receptor sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. It provides effective, temporary relief of sneezing, watery and itchy eyes, and runny nose due to hay fever and other upper respiratory allergies.

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.