the invention is directed to capsule systems for the delivery of active agents , particularly retinoids . in a preferred example , it is known that the compound tazarotene , known chemically as ethyl 6 -[( 4 , 4 - dimethylthiochroman - 6 - yl ) ethynyl ]- nicotinate , having the molecular formula c 21 h 21 no 2 s , is active in the treatment of acne and psoriasis . substantially increased activity of the active agent in this regard is expected if oral delivery can be effected . however , the solubility of tazarotene in water is negligible . the capsule of the present invention takes advantage of the tazarotene property of rapid systemic elimination ( see t ½ in table ii ), not exhibited by other currently available retinoids for acne and psoriasis , such as isotretinoin , acitretin , and etretinate . the capsule of the present invention provides high and reliable oral absorption of tazarotene thus it produces effective therapeutic concentrations in man upon oral ingestion . the rapid system elimination is important for many patients , especially for women of child - bearing age . upon cessation of oral tazarotene treatment , tazarotene is rapidly cleared from the body and poses little risks of teratogenic effects . the typical precautionary pregnancy wash - out periods for women of child - bearing age who just get off treatment of isotretinoin , acitretin , and etretinate are one month , three years , and for indefinite period of time , respectively . in general , a capsule system in further accordance with the present invention includes a soft gelatin capsule containing an active retinoid having low aqueous solubility , such as tazarotene , which is fully solubilized in a liquid triglyceride solution . the gelatin in accordance with the present invention may be derived from bovine sources which provides a capsule shell plasticized by , for example , glycerin . any suitable capsule shell formulation may be utilized which provides a means for not only encapsulating the retinoid active agent , but also for releasing same upon ingestion into a gastro - intestinal tract . it should also be appreciated that the system in accordance with the present invention may also contain conventional additional adjuvant substances which are conventionally used in the manufacture of drug capsules for providing consistency or facilitate the manufacture of the capsule . a lipophilic vehicle , such as a medium chain triglyceride , and more , specifically a caprylic / capric triglyceride is provided for active agent dissolution . importantly , the retinoid agent , tazarotene , is fully dissolved in the vehicle in a conventional manner before incorporation into the capsule shell . the total dissolution of tazarotene in the vehicle facilitates absorption from the gastro - intestinal tract by eliminating the need for drug dissolution prior to absorption . utilizing caprylic / capric triglyceride has been found that up to about 34 mg of tazarotene can be effectively solubilized in a capsule . in other words , the tazarotene is made particularly biologically available and can be absorbed by the body , although it is hard to dissolve in aqueous solutions , such as gastric juices . emulsifier means in accordance with the present invention is provided for promoting self - emulsion of the active agent and the vehicle in the gastro - intestinal tract . preferably , emulsifier means includes a co - emulsifier system which matches the hlb requirements of the medium chain triglyceride , i . e ., caprylic / capric triglyceride . this self - emulsion occurs in the gastro - intestinal tract following the gelatin shell opening . more specifically , the co - emulsifier system includes sorbitan monooleate nf , and polysorbate 80 nf , which are commercially available . butylated hydroxyanisole nf ( also commercially available ), is added as an antioxidant to stabilize the tazarotene . in addition , a colorant , such as , for example , titanium dioxide , is added to the shell formulation in order to provide protection of the tazarotene from light which may otherwise cause degradation thereof . otherwise , the shell may be conventionally formed of , for example , gelatin and glycerin . the composition of two representative strengths of tazarotene soft gelatin capsules is shown in table 1 . a person skilled in the art would appreciate that the composition of the fill formulation shown in table 1 may be altered somewhat to optimize the solubilization and / or emulsification of the drug . additionally , the person of skill in the art would appreciate that the capsule systems and fill formulations disclosed herein would be suitable for retinoids other than tazarotene . 2 . under yellow lights and a blanket of nitrogen , the following ingredients are added to the cct while mixing , allowing each to fully dissolve before adding next : 5 . the batch is then encapsulated using the procedure described in soft gelatin encapsulation . 1 . the encapsulation machine is of the rotary die type . it is fed by two receivers , one contains the molten gelatin mass used to form the shell , while the other contains the fill formulation . 2 . the encapsulation machine provides a continuous form , fill , and seal operation . a . the molten gelatin mass flows by gravity through heated tubes to two heated spreader boxes . the spreader boxes simultaneously cast the gelatin mass into two ribbons . these are lubricated with a blend of fractionated coconut oil / lecithin and delivered to the rotary dies . b . the fill formulation flows by gravity into a hopper which serves as a reservoir to the input of the encapsulation pump . the fill formulation is delivered to the filling point by the positive displacement piston pump . c . the two gelatin ribbons are fed in between the two rotating dies . the dies contain paired pockets which form the shape of the soft gelatin capsule and provide the sealing mechanism . at the precise moment that the two die pockets line up , the fill formulation is injected through an encapsulation wedge in between the gelatin ribbons . the seal forms as a result of the pressure between dies and heat applied by the encapsulation wedge to produce the soft gelatin capsule . 3 . the capsules are then dried by a two phase process : a . the capsules are moved to a rotary drier attached to the encapsulation machine . they are tumbled in a warm , low humidity , forced air environment for a predetermined length of time as specified in the batch records . b . the second phase begins after discharge from the rotary drier . the capsules are spread in a monolayer on shallow drying trays and low humidity air passed over them . transfer of water to and from the shell occurs over several days until the water put into the gelatin during gelatin mass production has evaporated . c . capsule hardness determinations are performed to monitor the drying process . the capsules are monitored until the hardness is within the specified range . the capsules are then placed into deep holding trays . 4 . capsules are inspected and polished with v . m . & amp ; p . naphtha to remove the lubricating film on the capsule surface , prior to grading and packaging . tazarotene soft gelatin capsules with the formulation set forth in table 1 have currently been shown to be physically and chemically stable through twelve months of storage at 25 ° c . as well as six months storage at 40 ° c . table ii , shows the plasma concentration of tazarotene following dosing of the capsules set forth in table i . table ii tazarotene dosage equivalents and steady - state pharmacokinetic parameters of tazarotenic acid in healthy subjects dosage 1 dosage 1 c max t max auc 0 - 24 t ½ 2 treatment ( mg / kg / day ) ( mg / m 2 / day ) ( mg / ml ) ( hr ) ( ng · hr / ml ) ( hr ) 0 . 2 mg / day ( with ensure ®) 0 . 003 0 . 12 5 . 24 ± 2 . 27 3 . 67 ± 1 . 51 30 . 6 ± 5 . 5 nc 3 0 . 7 mg / day ( with ensure ®) 0 . 010 0 . 40 19 . 9 ± 6 . 6 2 . 83 ± 0 . 98 101 ± 40 6 . 82 ± 1 . 66 0 . 7 mg / day ( with water ) 0 . 010 0 . 40 18 . 9 ± 4 . 6 3 . 00 ± 1 . 55 94 . 1 ± 10 . 6 6 . 43 ± 1 . 67 1 . 4 mg / day ( with ensure ®) 0 . 020 0 . 81 36 . 6 ± 8 . 5 1 . 83 ± 0 . 75 179 ± 39 9 . 41 ± 3 . 69 2 . 1 mg / day ( with ensure ®) 0 . 030 1 . 21 44 . 3 ± 13 . 9 4 . 17 ± 2 . 04 219 ± 25 8 . 9 ± 1 . 7 the results shown indicate effective levels of tazarotene in plasma immediately following ingestion of the drug capsule system in accordance with the present invention when taken with and without a liquid nutritional supplement that simulates food . these plasma concentration levels may be sufficient to effect a treatment of acne in a patient . although there has been hereinabove described a specific capsule system and method for the purpose of illustrating the manner in which the invention may be used to advantage , it should be appreciated that the invention is not limited thereto . accordingly , any and all modifications , variations , or equivalent arrangements which may occur to those skilled in the art , should be considered to be within the scope of the present invention as defined in the appended claims .
a capsule system for oral delivery of an active agent having low aqueous solubility generally includes , in combination with the active agent , a vehicle for preventing initial active agent dissolution within the gastrointestinal tract and an emulsifier for promoting self - emulsification of the active agent and vehicle in the gastrointestinal tract . a capsule shell is provided for encapsulating the active agent , vehicle and emulsifier with the shell being formulated to open upon ingestion into the gastrointestinal tract and release the active agent and vehicle .