Drugs suspended

Table 1.2 Drugs suspended from most but not all markets in the European Union and the United States.

The active ingredients in MDIs are usually water-soluble and chlorofluorocarbon- or hydrofluorocarbon-insoluble. Some CFC and HFA formulations use ethanol as a suspending agent by using an ethanol-insoluble salt form of the drug. Since the vehicle in MDIs must be propellant-based, a product with the drug suspended in the propellant may be the most stable dosage form. 

Percent inhibition of swelling after i.m. application of drug suspended in Tyrode solution. 

An equation relating the rate of release of solid drugs suspended in ointment bases into perfect sinks is derived.. . . The amount of drug released. .. is proportional to the square root of time. 

A reservoir, containing drug suspended or dissolved in liquefied gas propellant... 

PMW == Estimated weeks 50% of mice protected from parasite challenge following a single subcutaneous dose of 400 mg base equivalent/kg drug suspended in BBCO. 

Estimated number of weeks 50% of mice were protected following a single subcutaneous 400 mg/kg dose of drug suspended in BBCO. 

Estimated number of weeks 50% of mice were protected following a single subcutaneous 400 mg/kg dose of drug suspended in BBCO. ) First drug injection was 400 mg/kg given 58 days after infection with Mycobacterium leprae subsequent injections were 200 mg/kg at intervals of 0.5, 1, or 2 months. 

Lipidic matrices are constituted by a drug suspended or dissolved in lipidic excipients in which the drug is embedded. 

We should stress that some cases of controlled release are not regulated by diffusion and are not detailed in this chapter. Some involve release controlled by chemical kinetics. For example, imagine a drug suspended in a water-insoluble polymer. The polymer slowly reacts with water and then dissolves. As the polymer dissolves, the drug will be released at a rate controlled by the polymer s hydrolysis. Alternatively, imagine an implantable pump that releases a drug in response to the patient s demand. While these cases involve controlled release, neither is controlled by diffusion, so neither is discussed here. 

An example of such a product is Sterile Medroxyprogestrone Acetate Suspension used for its contraceptive property. Such an injection is designed to provide up to three months of contraceptive activity. Another such product is a depot injection of leuprolode acetate, an analogue of gonadatropin-releasing hormone (see Drug delivery systems). In this case, the product is a sterilized powder of microspheres to be suspended upon the addition of an appropriate diluent and intended for monthly injection. 

Phospholipids e.g. form spontaneously multilamellar concentric bilayer vesicles73 > if they are suspended e.g. by a mixer in an excess of aqueous solution. In the multilamellar vesicles lipid bilayers are separated by layers of the aqueous medium 74-78) which are involved in stabilizing the liposomes. By sonification they are dispersed to unilamellar liposomes with an outer diameter of 250-300 A and an internal one of 150-200 A. Therefore the aqueous phase within the liposome is separated by a bimolecular lipid layer with a thickness of 50 A. Liposomes are used as models for biological membranes and as drug carriers. 

Topical corticosteroids vary in potency, depending on tiie concentration of the drug (percentage), the vehicle in which the drug is suspended (lotion, cream, aerosol spray), and the area to which the drug is applied (open or denuded skin, unbroken skin, thickness of the skin over tiie treated area). 

Several variations of the solvent removal technique were developed (6,7). For the PCPP-SA, 20 80, M = 16,000, microspheres were prepared as follows 1 g polymer was dissolved in 1 ml methylene chloride, drug or dye was suspended in the solution, mixed, dropped into silicon oil containing 1-5% of Span 85, and stirred at a known stirring rate. Stirring was done using an overhead stirrer and a three-blade impeller. After 1 hr, petroleum ether was introduced and stirring was continued for another hour. The microspheres were isolated by filtration, washed with petroleum ether, dried overnight in a lyophilizer, sieved, and stored in a freezer. 

In this case a different method was used 2 g polymer was dissolved in 10 ml of methylene chloride, drug was added, and the mixture was suspended in silicon oil containing Span 85 and a known amount of methylene chloride. The amount of methylene chloride depended on the type and molecular weight of the polymer used. For example. 

A solid can be incorporated directly into an already congealed system in several ways. This is accomplished on a small scale by levigating the solid with a small portion of the total base it is to be suspended in to obtain a paste-like mass. The drug is worked into the... 

Orally administered suspensions containing a wide class of active ingredients (e.g., antibiotics, antacids, radiopaque agents) are of major commercial importance. The solids content of an oral suspension may vary considerably. For example, antibiotic preparations may contain 125-500 mg solid drug per 5 mL or a teaspoonful dose, while a drop concentrate may provide the same amount of drug in only 1-2 mL. Antacid or radiopaque suspensions also contain relatively high amounts of suspended material for oral administration. The suspending vehicle can, for example, be a syrup, sorbitol solution, or gum-thickened water with added... 

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