Mifenac K

Uses

Diclofenac Sodium ophthalmic preparation is used for-

• Inhibition of miosis during cataract surgery.
• Post-operative inflammation after cataract surgery and other ocular surgical procedures.
• Pre-operative and post-operative prevention of cystoid macular edema (CME) associated with lens extraction & intraocular lens implantation.
• Post-traumatic inflammation in penetrating and non- penetrating wounds (as an adjuvant to local anti-infective therapy).
• Non-infected chronic conjunctivitis, keratoconjunctivitis.

Antiulcerant Indication: Misoprostol is used for reducing the risk of NSAID (nonsteroidal anti-inflammatory drugs, including aspirin) induced gastric ulcers in patients at high risk of complications from gastric ulcer, eg, the elderly and patients with concomitant debilitating disease, as well as patients at high risk of developing gastric ulceration, such as patients with a history of ulcer. Misoprostol has not been shown to reduce the risk of duodenal ulcers in patients taking NSAIDs. Misoprostol should be taken for the duration of NSAID therapy. It had no effect, compared to placebo, on gastrointestinal pain or discomfort associated with NSAID use.

Gynecological Indication: Labor induction (in unfavorable cervical conditions) In the prevention & treatment of Postpartum Hemorrhage (PPH)

Mifenac K is also used to associated treatment for these conditions: Actinic Keratosis (AK), Acute Arthritis, Acute Gouty Arthritis, Acute Migraine, Acute Musculoskeletal Pain, Ankylosing Spondylitis (AS), Common Cold, Fever, Gouty Arthritis, Inflammation, Inflammatory Disease of the Oral Cavity, Inflammatory Disease of the throat, Inflammatory Reaction of the Nerve, Joint Pain, Juvenile Idiopathic Arthritis (JIA), Menstrual Distress (Dysmenorrhea), Muscle Inflammation, Ocular Inflammation, Operation site inflammation, Osteoarthritis (OA), Osteoarthritis of the Knee, Pain, Pain, Nerve, Pericarditis, Photophobia, Postoperative pain, Primary Dysmenorrhoea, Radicular Pain, Rheumatic Pain, Rheumatism, Rheumatoid Arthritis, Seasonal Allergic Conjunctivitis, Soreness, Muscle, Spinal pain, Tendon pain, Vertebral column pain, Acute Musculoskeletal injury, Acute, moderate, severe Pain, Inflammatory, Localized soft tissue rheumatism, Mild to moderate joint pain, Mild to moderate pain, Minor pain, Perioperative miosisGastric Ulcer, Incomplete Abortion, Missed Abortion, Postpartum Haemorrhage (PPH), Induction of cervix ripening therapy, Medically induced abortion

How Mifenac K works

Diclofenac inhibits cyclooxygenase-1 and -2, the enzymes responsible for production of prostaglandin (PG) G₂ which is the precursor to other PGs. These molecules have broad activity in pain and inflammation and the inhibition of their production is the common mechanism linking each effect of diclofenac.

PGE₂ is the primary PG involved in modulation of nociception. It mediates peripheral sensitization through a variety of effects. PGE₂ activates the G_q-coupled EP₁ receptor leading to increased activity of the inositol trisphosphate/phospholipase C pathway. Activation of this pathway releases intracellular stores of calcium which directly reduces action potential threshold and activates protein kinase C (PKC) which contributes to several indirect mechanisms. PGE₂ also activates the EP₄ receptor, coupled to G_s, which activates the adenylyl cyclase/protein kinase A (AC/PKA) signaling pathway. PKA and PKC both contribute to the potentiation of transient receptor potential cation channel subfamily V member 1 (TRPV1) potentiation, which increases sensitivity to heat stimuli. They also activate tetrodotoxin-resistant sodium channels and inhibit inward potassium currents. PKA further contributes to the activation of the P2X3 purine receptor and sensitization of T-type calcium channels. The activation and sensitization of depolarizing ion channels and inhibition of inward potassium currents serve to reduce the intensity of stimulus necessary to generate action potentials in nociceptive sensory afferents. PGE₂ act via EP₃ to increase sensitivity to bradykinin and via EP₂ to further increase heat sensitivity. Central sensitization occurs in the dorsal horn of the spinal cord and is mediated by the EP₂ receptor which couples to G_s. Pre-synaptically, this receptor increases the release of pro-nociceptive neurotransmitters glutamate, CGRP, and substance P. Post-synaptically it increases the activity of AMPA and NMDA receptors and produces inhibition of inhibitory glycinergic neurons. Together these lead to a reduced threshold of activating, allowing low intensity stimuli to generate pain signals. PGI₂ is known to play a role via its G_s-coupled IP receptor although the magnitude of its contribution varies. It has been proposed to be of greater importance in painful inflammatory conditions such as arthritis. By limiting sensitization, both peripheral and central, via these pathways NSAIDs can effectively reduce inflammatory pain.

PGI₂ and PGE₂ contribute to acute inflammation via their IP and EP₂ receptors. Similarly to β adrenergic receptors these are G_s-coupled and mediate vasodilation through the AC/PKA pathway. PGE₂ also contributes by increasing leukocyte adhesion to the endothelium and attracts the cells to the site of injury. PGD₂ plays a role in the activation of endothelial cell release of cytokines through its DP₁ receptor. PGI₂ and PGE₂ modulate T-helper cell activation and differentiation through IP, EP₂, and EP₄ receptors which is believed to be an important activity in the pathology of arthritic conditions. By limiting the production of these PGs at the site of injury, NSAIDs can reduce inflammation.

PGE₂ can cross the blood-brain barrier and act on excitatory G_q EP₃ receptors on thermoregulatory neurons in the hypothalamus. This activation triggers an increase in heat-generation and a reduction in heat-loss to produce a fever. NSAIDs prevent the generation of PGE₂ thereby reducing the activity of these neurons.

Misoprostol is a synthetic prostaglandin E1 analog that stimulates prostaglandin E1 receptors on parietal cells in the stomach to reduce gastric acid secretion. Mucus and bicarbonate secretion are also increased along with thickening of the mucosal bilayer so the mucosa can generate new cells.

Misoprostol binds to smooth muscle cells in the uterine lining to increase the strength and frequency of contractions as well as degrade collagen and reduce cervical tone.

Dosage

Mifenac K dosage

Ophthalmic (Adult)-

• Postoperative ocular inflammation: Instill into the appropriate eye 4 times daily starting 24 hr after surgery for up to 28 days.
• Inflammation and discomfort after strabismus surgery: Instill 1 drop 4 times daily for the 1st wk; then tid in the 2nd wk, bid in the 3rd wk, and as required for the 4th wk.
• Pain and discomfort after radial keratotomy: Instill 1 drop before surgery followed by 1 drop immediately after surgery, and then 1 drop 4 times daily for up to 2 days.
• Pain after accidental trauma: Instill 1 drop 4 times daily for up to 2 days.
• Control of inflammation after argon laser trabeculoplasty:Instill 1 drop 4 times during the 2 hr before procedure followed by 1 drop 4 times daily, up to 7 days after procedure.
• Prophylaxis of intra-operative miosis: Instill into appropriate eye 4 times w/in 2 hr before surgery.
• Post-photorefractive keratectomy pain:Instill into the affected eye twice, an hr before surgery, then 1 drop twice at 5-min intervals immediately after surgery, then every 2-5 hr while awake for up to 24 hr.
• Seasonal allergic conjunctivitis:Instill 1 drop before surgery followed by 1 drop immediately after surgery, and then 1 drop 4 times daily for up to 2 days.

Anti-ulcerant dosage & administration:

• The recommended adult oral dose for reducing the risk of NSAID-induced gastric ulcers:200 mcg Misoprostolfour times daily with food. If this dose cannot be tolerated, a dose of 100 mcg can be used. Misoprostolshould be taken for the duration of NSAID therapy as prescribed by the physician. Misoprostol should be taken with a meal, and the last dose of the day should be at bedtime.
• Renal impairment: Adjustment of the dosing schedule in renally impaired patients is not routinely needed, but dosage can be reduced if the 200 mcg dose is not tolerated.

Gynecological dosage & administration-

• Induction of Labor: 25 mcg vaginally 6 hourly or, 50 mcg orally 4 hourly.
• Postpartum Hemorrhage (PPH) prophylaxis: 400 mcg to 600 mcg orally or rectally immediately following delivery of the child.
• Postpartum Hemorrhage (PPH) treatment: 1,000 mcg rectally or, 200 mcg orally with 400 mcg sublingually.

Side Effects

Mild to moderate burning sensation in 5-15% patients which is transient in nature and almost never necessitated discontinuation of treatment. Other less common side-effects are sensitivity to light, bad taste, feeling of pressure, allergic reactions etc.

Gastrointestinal: GI disorders had the highest reported incidence of adverse events for patients receiving Misoprostol. It can cause more abdominal pain, diarrhea and other GI symptoms. The incidence of diarrhea can be minimized by administering it with food and by avoiding co administration with magnesium-containing antacids.

Gynecological: Gynecological disorders such as spotting, cramps, hypermenorrhea, menstrual disorder and dysmenorrhea have been reported. Postmenopausal vaginal bleeding may be related to Misoprostol administration.

Elderly: Overall, there were no significant differences in the safety profile in patients 65 years of age or older compared with younger patients.

Toxicity

Symptoms of overdose include lethargy, drowsiness, nausea, vomiting, and epigastric pain, and gastrointestinal bleeding. Hypertension, acute renal failure, respiratory depression and coma occur rarely. In case of overdose, provide supportive care and consider inducing emesis and administering activated charcoal if overdose occurred less than 4 hours prior.

The oral LD₅₀ in rats is 81mg/kg and in mice is 27mg/kg. The intraperitoneal LD₅₀ in rats is 40mg/kg and in mice is 70mg/kg.

Patients experiencing an overdose may present with sedation, tremor, convulsions, dyspnea, abdominal pain, diarrhea, fever, palpitations, hypotension, and bradycardia. Hemodialysis is not expected to be useful in the treatment of misoprostol overdose but oral activated charcoal may help reduce absorption. In the event of an overdose, treat symptoms with supportive therapy. This may include removal of undissolved tablets from the vagina or buccal cavity, intravenous fluid replacement, acetaminophen, diazepam, haloperidol, or intramuscular diclofenac depending on the symptoms that present.

Precaution

Diclofenac eye drops may mask the signs of infection. So physicians should be alert to the development of infections in patients receiving the drug. During prolonged use, it is recommended that physicians conduct periodic examinations of the eye, including measurement of the intraocular pressure. Contact lenses should not be worn during treatment.

Precaution should be taken in conditions where hypertension might precipitate severe complications (e.g. cerebrovascular and cardiovascular disease).

Interaction

No drug interaction is reported. There should be at least 5 minutes interval when another ophthalmic solution (e.g., steroid) is given.

There is no evidence of clinically significant interaction between Misoprostol and cardiac, pulmonary and CNS drugs and NSAIDs. Bioavailability of Misoprostol is decreased with high doses of antacid.

Volume of Distribution

Diclofenac has a total volume of distribution of 5-10 L or 0.1-0.2 L/kg. The volume of the central compartment is 0.04 L/kg. Diclofenac distributes to the synovial fluid reaching peak concentration 2-4h after administration. There is limited crossing of the blood brain barrier and cerebrospinal fluid concentrations only reach 8.22% of plasma concentrations. Doses of 50 mg delivered via intramuscular injection produced no detectable diclofenac concentrations in breast milk, however metabolite concentrations were not investigated. Diclofenac has been shown to cross the placenta in mice and rats but human data is unavailable.

Data regarding the volume of distribution of misoprostol is scarce.

The apparent volume of distribution of the active metabolite of misoprostol was in subjects with normal renal function was 13.6±8.0L/kg, with mild renal impairment was 17.3±23.0L/kg, with moderate renal impairment was 14.3±6.8L/kg, and with end stage renal disease was 11.0±9.6L/kg.

Elimination Route

Diclofenac is completely absorbed from the GI tract but likely undergoes significant first pass metabolism with only 60% of the drug reaching systemic circulation unchanged . Many topical formulations are absorbed percutaneous and produce clinically significant plasma concentrations. Absorption is dose proportional over the range of 25-150 mg. Tmax varies between formulations with the oral solution reaching peak plasma concentrations in 10-40min, the enteric coated tablet in 1.5-2h, and the sustained- and extended-release formulations prolonging Tmax even further. Administration with food has no significant effects on AUC but does delay Tmax to 2.5-12h.

For an 800µg oral dose of misoprostol, the AUC was 2.0192±0.8032h*ng/mL, the C_max was 2.6830±1.2161ng/mL, and a t_max of 0.345±0.186h. For a 800µg sublingual dose of misoprostol, the AUC was 3.2094±1.0417h*ng/mL, the C_max was 2.4391±1.1567ng/mL, and a t_max of 0.712±0.415h. For a 800µg buccal dose of misoprostol, the AUC was 2.0726±0.3578h*ng/mL, the C_max was 1.3611±0.3436ng/mL, and a t_max of 1.308±0.624h.

Half Life

The terminal half-life of diclofenac is approximately 2 h, however the apparent half-life including all metabolites is 25.8-33 h.

The half life of an 800µg oral dose is 1.0401±0.5090h, for a sublingual dose is 0.8542±0.1170h, and for a buccal dose is 0.8365±0.1346h.

Clearance

Diclofenac has a plasma clearance 16 L/h.

Because of the rapid de-esterification of misoprostol before or during absorption, it is usually undetectable in plasma. Misoprostol's active metabolite, misoprostol acid, has a total body clearance of 0.286L/kg/min. Subjects with mild renal impairment had a total body clearance of 0.226±0.073L/kg/min, subjects with moderate renal impairment had a total body clearance of 0.270±0.103L/kg/min, and subjects with end stage renal disease had a total body clearance of 0.105±0.052L/kg/min.

Elimination Route

Diclofenac is mainly eliminated via metabolism. Of the total dose, 60-70% is eliminated in the urine and 30% is eliminated in the feces. No significant enterohepatic recycling occurs.

As much as 73.2±4.6% of a radiolabelled oral dose of misoprostol is recovered in the urine.

Pregnancy & Breastfeeding use

The safety of Diclofenac eye drops in pregnancy & lactation has not been established and its use therefore is not recommended unless the potential benefit to the mother outweighs the possible risk to the child.

Pregnancy: Misoprostol is contraindicated to pregnant women.

Lactation: It is not known whether Misoprostol's active metabolite- misoprostol acid is excreted in human milk. Misoprostol should not be administered to nursing mothers because the excretion of misoprostol acid could cause diarrhea in nursing infants.

Contraindication

Hypersensitivity to any of the components Like other non steroidal anti-inflammatory agents, Diclofenac Sodium eye drops is contraindicated in patients in whom attacks of asthma, urticaria or acute rhinitis have been observed following application of acetyl salicylic acid or other cyclo-oxygenase inhibitors

Misoprostol is contraindicated to anyone with a history of allergy to prostaglandins and it is also contraindicated in pregnancy.

Acute Overdose

Accidental ingestion of Diclofenac Sodium presents virtually no risk of unwanted effects, since one 5 ml bottle of eye drop solution contains only 5 mg of Diclofenac Sodium, which is equivalent to about 3% of the recommended maximum oral dose for adults.

The toxic dose of Misoprostol in human has not been determined. Clinical signs that may indicate an overdose are sedation, tremor, convulsions, dyspnea, abdominal pain, diarrhea and fever. Symptoms should be treated with supportive therapy.

Storage Condition

Close the bottle immediately after use. Do not use for more than four weeks after opening. Store at room temperature.

Store in a cool and dry place, protected from light and moisture. Keep out of the reach of the children

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