Pharmacological action The chemical structure of this product is similar to acetazolamide (there is one methyl group on the nitrogen atom). Therefore, the pharmacological action and mechanism are the same as acetazolamide. Compared with acetazolamide, methazolamide's structural design reduces ionization, and its intraocular permeability is enhanced. The function of this product through blood aqueous humor and blood-brain barrier is also stronger than acetazolamide (the concentration of human cerebrospinal fluid is 50 times higher than acetazolamide). The inhibitory effect of carbonic anhydrase is 60% stronger than that of acetazolamide. In vivo, only 55% of methazolamide binds to plasma protein (whereas acetazolamide binds to plasma protein 90% ~ 95%). Because only the unbound part of the drug dose has pharmacological effect, the lower dose has obvious intraocular pressure reduction reaction. Methazolamide can inhibit the generation of aqueous humor, which can be reduced by 40% in most patients. After oral administration of 1 ~ 2 hours, the intraocular pressure decreased for 16 ~ 18 hours. The antihypertensive effect of this product is dose-dependent. Oral administration of 25, 50 and 100mg and 1 time every 8 hours can reduce intraocular pressure by 3.3, 4.3 and 5.6mmHg respectively.
Pharmacokinetics This product is well absorbed by gastrointestinal tract, which is slightly slower than acetazolamide. There is a linear relationship between serum concentration and dose. The binding rate of plasma protein was 55%, which was lower than that of acetazolamide (90%). In the range of plasma pH, 39% of methazolamide is in non-ionized state. After oral administration of 100mg, the serum peak appeared 2-3 hours after taking the medicine, and the peak concentration was about 17μg/ml, and the peak concentration remained constant for at least 8 hours. Methazolamide is more fat-soluble and water-soluble than acetazolamide, which is helpful for drug reabsorption from renal tubules, increasing drug half-life and blood concentration. The plasma half-life is about 65438 04 hours, which is significantly longer than acetazolamide. 25% of the product is in prototype form, and 75% is excreted in urine as metabolites.
Indications are used for adjuvant treatment of primary open-angle glaucoma, angle-closure glaucoma and some secondary glaucoma, as well as patients with unsatisfactory intraocular pressure control of local anti-glaucoma drugs. The curative effect of this product on patients with severe obstructive pulmonary disease is better than acetazolamide, because it can reduce intraocular pressure and has little effect on acid-base balance. Methazolamide has less effect on urinary citrate secretion than acetazolamide, so methazolamide is recommended for patients who need oral carbonic anhydrase inhibitors but are prone to kidney calculi.
Usage and Dosage: 25mg for the first oral administration for adults, twice a day. This dose can often reduce intraocular pressure by 4 ~ 5 mmHg, with minimal side effects. If the effect of lowering intraocular pressure after medication is not satisfactory, the dosage can be increased to 50mg, twice a day.
Adverse reactions 1. It is reported that methazolamide can cause serious adverse blood reactions, including aplastic anemia and agranulocytosis. 2. It is reported that taking methazolamide can cause kidney calculi, but it is very rare. 3. There are some adverse reactions such as nausea, anorexia, abnormal sensation, discomfort, fatigue and skin erosion.
Taboo 1. Patients with hyponatremia, hypokalemia, hyperchloric acidosis, adrenal failure, adrenocortical hypofunction (Addison's disease) and hepatic coma are prohibited. 2. Patients with a history of sulfanilamide allergy are prohibited.
Precautions 1. Use with caution in patients with metabolic acidosis and hypokalemia. 2. methazolamide should not be used instead of surgery for angle-closure glaucoma, otherwise it may cause permanent adhesive angle closure. 3. This product cannot be used to control intraocular pressure for a long time.
Interactive 1. The combination of carbonic anhydrase inhibitor and high dose aspirin can lead to serious metabolic disorder. Therefore, salicylic acid preparation should be used with caution. 2. Low dose of methazolamide itself will not cause hypokalemia, but carbonic anhydrase inhibitors can increase the potassium excretion of other drugs. 3. Combined use with adrenocorticotropic hormone and glucocorticoid can lead to severe hypokalemia, and attention should be paid to monitoring serum potassium concentration and cardiac function when combined use. It should also be estimated that long-term simultaneous use may increase the risk of hypocalcemia and lead to osteoporosis, because these drugs increase calcium excretion.
Pregnant and lactating women take 1. This product can cause deformities in rodents, so pregnant women should avoid taking it. 2. It is not clear whether this product is secreted into the emulsion, and lactating women should stop breastfeeding if they need to be treated with this product.
The safety and effectiveness of this product for children are still unclear.
The elderly and adults have good tolerance to this product, so this product is suitable for elderly patients.