DESCRIPTION
Domperidone – A specific blocker of dopamine receptors. It speeds gastrointestinal peristalsis, causes prolactin release, and is used as antiemetic and tool in the study of dopaminergic mechanisms. Paracetamol – Acetaminophen, also known as paracetamol, is commonly used for its analgesic and antipyretic effects. Its therapeutic effects are similar to salicylates, but it lacks anti-inflammatory, antiplatelet, and gastric ulcerative effects.
CATEGORIES
Domperidone – Antiemetics, GIT Regulators & Anti-Inflammatories . Paracetamol – Analgesics, Non-Narcotic,Antipyretics.
CHEMICAL FORMULA
Domperidone – C22H24ClN5O2,Paracetamol – C8H9NO2.
COMPOSITION
Domperidone 10 mg + paracetamol 325 mg
INDICATION
Domperidone – For management of dyspepsia, heartburn, epigastric pain, nausea, and vomiting. Paracetamol – For temporary relief of fever, minor aches, and pains.
PHARMACODYNAMICS
Domperidone – Domperidone is a specific blocker of dopamine receptors. It speeds gastrointestinal peristalsis, causes prolactin release, and is used as antiemetic and tool in the study of dopaminergic mechanisms. Paracetamol – Acetaminophen (USAN) or Paracetamol (INN) is a widely used analgesic and antipyretic drug that is used for the relief of fever, headaches, and other minor aches and pains. It is a major ingredient in numerous cold and flu medications and many prescription analgesics. It is extremely safe in standard doses, but because of its wide availability, deliberate or accidental overdoses are not uncommon. Acetaminophen, unlike other common analgesics such as aspirin and ibuprofen, has no anti-inflammatory properties or effects on platelet function, and it is not a member of the class of drugs known as non-steroidal anti-inflammatory drugs or NSAIDs. At therapeutic doses acetaminophen does not irritate the lining of the stomach nor affect blood coagulation, kidney function, or the fetal ductus arteriosus (as NSAIDs can). Like NSAIDs and unlike opioid analgesics, acetaminophen does not cause euphoria or alter mood in any way. Acetaminophen and NSAIDs have the benefit of being completely free of problems with addiction, dependence, tolerance and withdrawal. Acetaminophen is used on its own or in combination with pseudoephedrine, dextromethorphan, chlorpheniramine, diphenhydramine, doxylamine, codeine, hydrocodone, or oxycodone.
MECHANISM
Domperidone – Domperidone acts as a gastrointestinal emptying (delayed) adjunct and peristaltic stimulant. The gastroprokinetic properties of domperidone are related to its peripheral dopamine receptor blocking properties. Domperidone facilitates gastric emptying and decreases small bowel transit time by increasing esophageal and gastric peristalsis and by lowering esophageal sphincter pressure. Antiemetic: The antiemetic properties of domperidone are related to its dopamine receptor blocking activity at both the chemoreceptor trigger zone and at the gastric level. It has strong affinities for the D2 and D3 dopamine receptors, which are found in the chemoreceptor trigger zone, located just outside the blood brain barrier, which – among others – regulates nausea and vomiting .Paracetamol – Acetaminophen is thought to act primarily in the CNS, increasing the pain threshold by inhibiting both isoforms of cyclooxygenase, COX-1, COX-2, and COX-3 enzymes involved in prostaglandin (PG) synthesis. Unlike NSAIDs, acetaminophen does not inhibit cyclooxygenase in peripheral tissues and, thus, has no peripheral anti-inflammatory affects. While aspirin acts as an irreversible inhibitor of COX and directly blocks the enzyme’s active site, studies have found that acetaminophen indirectly blocks COX, and that this blockade is ineffective in the presence of peroxides. This might explain why acetaminophen is effective in the central nervous system and in endothelial cells but not in platelets and immune cells which have high levels of peroxides. Studies also report data suggesting that acetaminophen selectively blocks a variant of the COX enzyme that is different from the known variants COX-1 and COX-2. This enzyme is now referred to as COX-3. Its exact
MECHANISM
of action is still poorly understood, but future research may provide further insight into how it works. The antipyretic properties of acetaminophen are likely due to direct effects on the heat-regulating centres of the hypothalamus resulting in peripheral vasodilation, sweating and hence heat dissipation.
ABSORPTION
Domperidone – Fast,Paracetamol – Rapid and almost complete
METABOLISM
Domperidone – Hepatic and intestinal (first-pass),Paracetamol – Acetaminophen primarily undergoes glucuronidation (45-55% of the dose) in which this process is facilitated by UGT1A1, UGT1A6, UGT1A9, UGT2B15 in the liver or UGT1A10 in the gut. 30-35% of the dose undergoes sulfation. This biotransformation is facilitated by SULT1A1, SULT1A3, SULT1A4, SULT1E1 and SULT2A1. A small percentage of acetaminophen is oxidized by CYP2E1 to form N-acetyl-p-benzo-quinone imine (NAPQI), a toxic metabolite which is then conjugated to glutathione and excreted renally. Studies suggest that CYP3A4 and CYP2E1 are the primary cytochrome P450 isozymes responsible for the generation of toxic metabolites. Accumulation of NAPQI may occur if primary metabolic pathways are saturated.
ELIMINATION
Domperidone – Breast milk, renal,Paracetamol – Approximately 80% of acetaminophen is excreted in the urine after conjugation and about 3% is excreted unchanged.
HALF LIFE
Domperidone – 7 hours,Paracetamol – 1 to 4 hours
TOXICITY
Domperidone – Side effects include galactorrhea, gynecomastia, or menstrual irregularities.Paracetamol -Oral, mouse: LD50 = 338 mg/kg; Oral, rat: LD50 = 1944 mg/kg. Acetaminophen is metabolized primarily in the liver, where most of it is converted to inactive compounds by conjugation with glucuronic acid and, to a lesser extent, sulfuric acid. Conjugates are then excreted by the kidneys. Only a small portion is excreted in unchanged in urine or oxidized via the hepatic cytochrome P450 enzyme system (CYP2E1). Metabolism via CYP2E1 produces a toxic metabolite, N-acetyl-p-benzoquinoneimine (NAPQI). The toxic effects of acetaminophen are due to NAPQI, not acetaminophen itself nor any of the major metabolites. At therapeutic doses, NAPQI reacts with the sulfhydryl group of glutathione to produce a non-toxic conjugate that is excreted by the kidneys. High doses of acetaminophen may cause glutathione depletion, accumulation of NAPQI and hepatic necrosis. The maximum daily dose of acetaminophen is 4 g. Liver failure has been observed at doses as low as 6 g per day. As such, the maximum daily and single dose of acetaminophen is currently being reviewed in some countries. N-acetyl-cysteine, a precursor of glutathione, may be administered in the event of acetaminophen toxicity.
FOOD INTERACTIONS
avoid alcohol
SIDE EFFECTS
Domperidone – Headache. Dry mouth. Good mouth care, sucking hard, sugar-free candy, or chewing sugar-free gum may help. See a dentist often .Paracetamol – Upset stomach or throwing up. Harm to the liver may rarely happen.