Nonquaternary cholinesterase reactivators. Dialkylaminoalkyl thioesters of alpha-ketothiohydroximic acids as reactivators of diisopropyl phosphorofluoridate inhibited acetylcholinesterase.

We have prepared a series of alpha-ketothiohydroximic acid thioesters and evaluated them in vitro with respect to their ability to reactivate (diisopropylphosphoryl)acetylcholinesterase. The compounds conform to the general formula RC(=O)C(=NOH)S(CH2)nNR2'.HCl, where R = CH3, C6H5, 4-CH3OC6H4, 4-NO2C6H4; n = 2, 3; and R' = CH3, C2H5, or i-C3h7. We also prepared 4-BrC6H4C(=NOH)S(CH2)2N(C2H5)2.HCl and 4-CH3OC6H4C(=O)C(=NOH)S(CH2)2N(C2H5)2.CH3I for comparison. The alpha-ketothiohydroximates exhibit oxime acid dissociation constants (pKa) in the range 6.9 to 8.4, bracketing the value of pKa = 7.9, believed to be optimal for acetylcholinesterase reactivation. The compounds are also good nucleophiles; bimolecular rate constants (kn) for reaction with p-nitrophenyl acetate follow the expression log (kn) = 6.7 - 0.69(14 - pKa = The reactivation of (diisopropylphosphoryl)acetylcholinesterase is highly dependent on the alpha-ketothiohydroximate structure: 4-h incubation of inhibited enzyme at pH 7.6, 25 degrees C, with 1 x 10(-3) M 4-CH3OC6H4C(=O)C(=NOH)S(CH2)3N(CH3)2.HCl gives no detectable restoration of activity, whereas 4-CH3OC6H4C(=O)C(=NOH)S(CH2)2N(C2H5)2.HCl restores inhibited enzyme activity to 58% of control under identical conditions. With alpha-ketothiohydroximate in excess over inhibited enzyme, the kinetics of reactivation are governed by an equilibrium constant (Kr) for binding alpha-ketothiohydroximate to the inhibited enzyme and a nucleophilic displacement rate constant (kr) for attack on phosphorus.

Nonquaternary cholinesterase reactivators. 2. Alpha-heteroaromatic aldoximes and thiohydroximates as reactivators of ethyl methylphosphonyl-acetylcholinesterase in vitro.

We prepared six pairs of alpha-heteroaromatic aldoximes, RC(= NOH)H, and thiohydroximates, RC(= NOH)S-(CH2)2N(C2H5)2, where R represents various oxadiazole and thiadiazole rings. Each compound was characterized with respect to the following: structure, (hydroxyimino)methyl acid dissociation constant, nucleophilicity toward trigonal carbon and tetrahedral phosphorus, octanol-buffer partition coefficient, reversible inhibition of eel acetylcholinesterase (AChE), and in vitro reactivation of AChE inhibited by ethyl p-nitrophenyl methylphosphonate. Eight of the twelve compounds significantly reactivate ethyl methylphosphonyl-AChE, but inherent reactivities are moderate to low: the most potent nonquaternary reactivator, 3-phenyl-5-[(hydroxyimino)methyl]-1,2,4-oxadiazole, is 17 times less reactive than the well-known reactivator 2-[(hydroxyimino)methyl]-1-methylpyridinium iodide (2-PAM). One of the nonquaternary compounds, 3-phenyl-1,2,4-oxadiazole-5-thiohydroximic acid 2-(diethylamino)ethyl S-ester, is a powerful reversible inhibitor of AChE (I50 = 7.5 microM). The observed relationships between nonquaternary compound structure, reactivation potency, and anti-AChE activity reveal important molecular requirements for high reactivity toward phosphonylated AChE.

Nonquaternary cholinesterase reactivators. 3. 3(5)-Substituted 1,2,4-oxadiazol-5(3)-aldoximes and 1,2,4-oxadiazole-5(3)-thiocarbohydroximates as reactivators of organophosphonate-inhibited eel and human acetylcholinesterase in vitro.

As an extension of an earlier investigation (J. Med. Chem. 1984, 27, 1431), we prepared a series of 3-substituted 5-[(hydroxyimino)methyl]-1,2,4-oxadiazoles and the corresponding 5-thiocarbohydroximic acid 2-(N,N-dialkylamino)ethyl S-esters. The compounds were evaluated in vitro as reactivators of phosphonylated electric eel and human erythrocyte (RBC) acetylcholinesterases (AChE). The compounds were characterized with respect to (hydroxyimino)methyl acid dissociation constant, nucleophilicity, octanol/buffer partition coefficient, reversible AChE inhibition, and kinetics of reactivating ethyl methylphosphonylated AChE. One compound was also tested for effectiveness in preventing AChE phosphonylation. All of the tested compounds significantly reactivate ethyl methylphosphonylated AChE: the 3-n-octyl- and 3-(1-naphthyl)-substituted aldoximes are as reactive (within a factor of 5-10) toward the inhibited enzymes as the benchmark pyridinium reactivators, 2-PAM and HI-6. All of the substituted thiocarbohydroximic acid S-esters are powerful reversible inhibitors of AChE's: the 3-n-octyl- and 3-(1-naphthyl)-substituted thiocarbohydroximates inhibit eel AChE to 50% initial activity at concentrations less than 5 microM. When added to an eel AChE solution at concentrations between 5 and 50 microM, the 3-phenyl-substituted thiocarbohydroximate effectively antagonizes AChE inhibition by ethyl p-nitrophenyl methylphosphonate (EPMP), suggesting the potential utility of this compound for preventing anti-AChE-agent poisoning.

Structure-activity relationships for reactivators of organophosphorus-inhibited acetylcholinesterase: quaternary salts of 2-[(hydroxyimino)methyl]imidazole.

A series of 1,3-disubstituted-2-[(hydroxyimino)methyl]imidazolium halides were prepared and evaluated in vitro with respect to their ability to reactivate acetylcholinesterase inhibited by ethyl p-nitrophenyl methylphosphonate (EPMP) and 3,3-dimethyl-2-butyl methylphosphonofluoridate (GD). The compounds conform to the general formula N(CH3)C(CHNOH)N(CH2OR)CHCH+ X Cl-, where R = CH3, (CH2)3CH3, (CH2)7CH3, CH2C6H5, CH2C10H7, (CH2)3C6H5, CH(CH3)2, CH2C(CH3)3, and CH(CH3)C(CH3)3. For comparison we also evaluated three known pyridinium reactivators, 2-PAM, HI-6, and toxogonin. The imidazolium aldoximes exhibit oxime acid dissociation constants (pKa) in the range 7.9-8.1, bracketing the value of 8.0, believed to be optimal for acetylcholinesterase reactivation. With imidazolium compound in excess over inhibited enzyme, the kinetics of reactivation are well behaved for EPMP-inhibited AChE and depend on the nature of the alkyl ether group R. For GD-inhibited AChE, maximal reactivation was used to compare compounds because rapid phosphonyl enzyme dealkylation and enzyme reinhibition complicate interpretation of kinetic constants.

Multidimensional column-switching liquid chromatographic method for dissolution testing of enprostil soft elastic gelatin capsules.

Enprostil (methyl 7-[(1 R,2R,3R)-3-hydroxy-2-[(E)-(3R)-3-hydroxy-4- phenoxy-1-butenyl]-5-oxocyclopentyl]-4,5-heptadienoate), an E-type prostaglandin exhibiting anti-ulcer activity, is formulated as a propylene carbonate solution filled into soft elastic gelatin (SEG) capsules. Enprostil SEG capsules were maintained for timed intervals at 50 degrees C, 30 degrees C, and room temperature, and the quantity of drug released upon complete capsule dissolution was determined as a function of storage condition. The dissolution test adhered to USP XXI guidelines (paddle method) and used a multidimensional HPLC technique to provide a sensitive and selective enprostil assay. Parallel HPLC assays determined the enprostil concentration in the propylene carbonate fill that was physically expressed from initially manufactured and from aged capsules. This corrected for any enprostil loss via chemical degradation on storage. The study included six different aged samples (six replicates each), and for all six samples, the enprostil recovered from dissolved capsules averaged 104 +/- 1.4% of the enprostil physically expressed from the capsules. Similarly, the enprostil recovered from dissolved, aged capsules averaged 103 +/- 5% of the enprostil physically expressed from capsules at the initial time point. These findings exclude the possibility that interactions with the SEG capsule wall reduce drug availability during storage under normal conditions. The multidimensional HPLC technique should generally extend to analysis of other noncationic drugs formulated into soft gelatin capsules.

Reactivity of enprostil stereoisomers in soft elastic gelatin capsules.

Enprostil (methyl 7-[(1R*,2R*,3R*)-3-hydroxy-2-[(E)-(3R*)-3-hydroxy-4-phenoxy-1-butenyl]- 5-oxocyclopentyl]-4,5-heptadienoate), a gastric acid secretion inhibitor and potent anti-ulcer drug, is formulated as a propylene carbonate solution which is filled into soft elastic gelatin capsules. The drug molecule features two unresolved asymmetric carbon atoms, and synthesis yields an equimolar mixture of four different optical isomers (two diastereomeric pairs of enantiomers). The objective of this study was to establish the degree to which enprostil does or does not degrade stereoselectively in the soft elastic gelatin capsule formulation. Accordingly, we developed an HPLC method capable of resolving enprostil diastereoisomers and applied the method to determining reaction rates of enprostil in soft elastic gelatin capsules maintained at 40 degrees C. The study included three soft elastic gelatin capsule lots: the first two contained an equimolar mixture of all four enprostil enantiomers; and the third contained an equimolar mixture of two individual diastereoisomers of known optical purity. Comparing enprostil degradation rates in the three capsule lots showed that reactivity ratios in all cases were (within the limits of experimental uncertainty) equal to unity. This observation conclusively excludes the possibility of significant enantioselectivity for enprostil degradation in the soft elastic gelatin capsule formulation. We also report kinetic equations for the general case of relating stereospecific reactivity ratios to drug product shelf life when drug concentrations are monitored with nonstereoselective analytical techniques.

Water soluble complexes of the antiviral drugs, 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine and acyclovir: the role of hydrophobicity in complex formation.

We investigated water-soluble complexes of various ligands with the antiviral drugs, 9-[(2-hydroxyethoxy)methyl]guanine (acyclovir) and 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine (DHPG). For comparison, we also examined the "parent" compounds, guanine and guanosine, as substrates for complex formation. Using the phase-solubility technique, we measured formation constant (K1) values at 23 degrees C in pH 7 buffer. For a single substrate, formation constants with different ligands varied in the order: caffeine greater than pyridoxine approximately cytidine greater than nicotinamide greater than sucrose. With caffeine as the ligand, formation constants with different substrates varied in the order: guanine greater than guanosine approximately acyclovir greater than DHPG. The largest formation constant observed was 58 M-1 (for guanine-caffeine), and the smallest formation constant was 0.29 M-1 (for DHPG-sucrose). Examining the literature for formation constant data on compounds related to DHPG, and comparing literature data with our own, reveals a significant correlation between formation constants and ligand hydrophobicity. For 41 substrate-ligand pairs, least squares linear regression analysis of log K1 values versus various parameters reflecting donor-acceptor abilities (e.g., substrate and ligand HOMO and LUMO values, or substrate oxidation potentials) failed to significantly correlate. We conclude that ligand hydrophobicity is a general determinant of water soluble complex formation, but not necessarily the exclusive or dominant controlling factor for all complexes. Charge-transfer interactions are not important determinants of complex formation for the substrate-ligand combinations that we have considered.

Electrochemistry of purine derivatives. 1: Direct determination for the antiviral drug 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine by anodic differential pulse voltammetry.

Differential pulse voltammetry at a stationary glassy carbon electrode was used for the sensitive and selective analysis of a potent new antiviral analogue of 2-deoxyguanosine in a pharmaceutical formulation. In the electrochemical method for analysis of 9-[1,(3-dihydroxy-2-propoxy)methyl] guanine (1), an electroactive internal standard (uric acid) was used. Linear peak current-concentration relationships were obtained at 1 concentrations of 0.4-2.0 mM, with a quantitation limit of 0.1 mM. Degraded solutions of 1 were assayed directly by differential pulse voltammetry and also by two chromatographic methods to demonstrate the specificity of the electrochemical method. The voltammetric method reliably provides accurate and reproducible results in considerably less time than conventional chromatographic analysis.

Electrochemistry of purine derivatives. 2: Correlation of anodic differential pulse peak potentials with Hammett substituent constants.

Differential pulse voltammetry was used to measure anodic peak potentials at the glassy carbon electrode (in pH 2 to 11 aqueous buffer versus Ag/AgCl) for 14 purine bases and nucleosides. The tested compounds included the antiviral drugs 9-[(1,3-dihydroxy-2-propoxy)-methyl]guanine (1) and acyclovir (2) plus six analogues of 1. At pH 7, representative peak potential values were as follows: 1, 0.97 V; 2, 1.01 V; 6-amino-6-deoxy-1 1.00 V; guanosine, 1.03 V; 2'-deoxyguanosine, 1.03 V. The observed potentials at pH 7 and related literature values correlated with Hammett pi(para) substituent constants. For 24 purines, stepwise multiple linear regression provided the relationship: P7 = (1.08 +/- 0.055) + (1.13 +/- 0.13) sigma 8 + (0.338 +/- 0.061)sigma(2 + 6) + (0.281 +/- 0.043)D (with n = 24, r2 = 0.930, CV = 11.1, and F = 88) where P7 is the pH 7 oxidation potential, the subscripts refer to purine ring substitution position, and D is an indicator variable for substitution at purine N9 by furanoside or glycoside analogue moieties. The observed relationship permits predictions of anodic peak potentials for other purines the substitution patterns of which are known.

Effects of PAM, proPAM, and DFP on behavior, thermoregulation, and brain AChE in rats.

The effects of pyridine-2 aldoxime methyl iodide (PAM), N-methyl-1,6-dihydro-pyridine-2-carbaldoxime hydrochloride (proPAM), and diisopropyl phosphorofluoridate (DFP) on performance of a conditioned avoidance response (CAR), body temperature, and in vivo acetylcholinesterase (AChE) activity in five brain regions in the rat were examined. Sublethal doses of DFP (1.5 to 2.5 mg/kg, IP) markedly degraded CAR performance. This effect was antagonized by 5 mg/kg, subcutaneously injected (SC) atropine. A 50 mg/kg, SC dose of PAM had no effect on the CAR, but an equal dose of proPAM caused a transient deterioration of performance. Given 10 min or 2 hr after DFP, 50 mg/kg proPAM initially exacerbated the behaviorally toxic effects of DFP. Neither PAM nor proPAM antagonized DFP-induced hypothermia. PAM did not reactivate DFP-inhibited brain AChE, and proPAM reactivated it by only 6 to 12% of control activity.

Kinetics of pramlintide degradation in aqueous solution as a function of temperature and pH.

The stability of the 37-amino acid peptide pramlintide, in aqueous solution, was studied as a function of pH and temperature. Samples of pramlintide formulated as a parenteral product were exposed to elevated temperatures and to realistic storage conditions for as long as 30 months. Pramlintide degradation was monitored by three high-performance liquid chromatography (HPLC) methods: a reversed-phase (RP-HPLC) and a strong-cation exchange (SCX-HPLC) method for percentage purity determination by area normalization, plus a second RP-HPLC method for potency determination versus external standards. The pH-rate profile for pramlintide shows increasing degradation rate constants with increasing pH over the range pH = 3.5 to 5.0. The Arrhenius expression for pramlintide degradation at pH = 4.0 over the temperature range 5 degrees C to 50 degrees C is ln(k(0))= 37.39-21.900/RT, where k(0) is the zero-order rate constant (in %/mo) for pramlintide degradation. The pramlintide parenteral product formulated at pH = 4.0 is extremely stable, with percentage purity and percentage potency loss of only approximately 2% over 30 months at 5 degrees C. The formulated pramlintide drug product has acceptable shelf life for long-term storage at 5 degrees C and up to a 30-day patient use when stored at ambient temperature.

Pramlintide injection drug product robustness studies.

The article examines the effects of temperature excursions and actual dose withdrawal on the quality of pramlintide injection, a multidose liquid parenteral formulation. Studies were designed to demonstrate product robustness under conditions that may occur during patient use. Pramlintide %Purity was determined by two high-performance liquid chromatography (HPLC) methods, a reversed-phase (RP-HPLC) and a strong-cation exchange (SCX-HPLC) method. A second RP-HPLC method was used to determine pramlintide potency and the concentration of the m-cresol preservative. Antimicrobial preservative effectiveness testing was per USP and European Pharmacopeia (Ph. Eur.). Short-term stability studies were undertaken to probe the effects of the following conditions: 5 degrees C to 40 degrees C and 5 degrees C to -20 degrees C temperature cycling over 10 days; once daily or four-times daily dose withdrawal over 12 or 42 days; and combined 30 degrees C storage and four-times daily dose withdrawal over 42 days. In all cases, pramlintide %Purity and potency values remained essentially unchanged or unchanged relative to controls. Similarly, product appearance, and m-cresol concentration and preservative effectiveness were not significantly affected by the stress conditions used in the 5 studies. Pramlintide injection drug product is extremely robust to challenging stress conditions that may occur during patient use of this multidose product for chronic administration.

Orthogonal HPLC methods for quantitating related substances and degradation products of pramlintide.

Pramlintide is a 37-amino acid peptide that is being evaluated as a drug candidate for treating people with type 1 and insulin-using type 2 diabetes. Two high-performance liquid chromatography (HPLC) methods were developed for quantitating related substance impurities in pramlintide drug substance as well as degradation products of pramlintide formulated for parenteral administration. The methods differ with respect to separation mode and therefore provide orthogonal information concerning related substances and degradation products. One method uses a reverse phase (RP) separation mode, and the other involves a strong cation exchange (SCX) separation. Method performance testing showed that the RP- and SCX-HPLC methods both afford a high degree of selectivity, accuracy, precision, and sensitivity. The limit of quantitation for determining spiked authentic samples of degradation products was shown to be approximately 0.1% (relative to intact pramlintide) for both methods. Relative retention times for known pramlintide degradation products were determined for both the RP- and SCX-HPLC methods, demonstrating the selectivities of the 2 methods as well as the orthogonality of the information. The methods were also shown to be diastereospecific with respect to separating pramlintide from authentic samples of D-isomers at Ala5, Ala8, Ala5-Ala8, and Leu12. The methods did not resolve pramlintide, however, from diastereomers with D-isomers near the C- and N-termini, namely Lys1,Cys2, and Tyr37.

Acid-catalyzed peptide bond hydrolysis of recombinant human interleukin 11.

Recombinant human interleukin 11 (rhIL-11) is a multispectrum cytokine that plays an important role in megakaryocytopoiesis and platelet production. Probing rhIL-11 chemical reactivity in aqueous solution is an important initial step in developing a dosage form for rhIL-11 clinical trials. This report documents rhIL-11 degradation kinetics at 50 degrees C in solutions adjusted to pH 3.0 to 9.5. Stressed samples were analyzed by reverse-phase HPLC and degradation product peaks were isolated for structural characterization. The results show maximal stability in the region pH 6.5 to 7.0. Degradation product identification shows that the major reaction pathway in acidic solution involves peptide cleavage at aspartate133-proline134. In alkaline solution, protein disappearance proceeds via nonspecific loss to container surfaces. Degradation products at alkaline pH have not been identified.

Determination of solute-polymer interaction properties and their application to parenteral product container compatibility evaluations.

Kinetic and thermodynamic interaction properties between dialkyl phthalate test compounds and a polyolefin polymer were examined via a permeation-cell experimental design. Disappearance and appearance rates of solute in the receptor and donor solutions, as well as the equilibrium composition of the test system, are used to determine sorption and diffusion coefficients and the solute/polymer equilibrium binding constant. Sorption rate constants and diffusion coefficients exhibit Arrenhius-type behavior. The binding constants obtained correlate well with the solute's octanol-water partition coefficient. The kinetic and thermodynamic data generated combine with proposed interaction models to identify solute/polymer interactions (binding and leaching) pertinent to evaluating container/solution compatibility for parenteral products.

Gamma irradiation effects on molecular weight and in vitro degradation of poly(D,L-lactide-CO-glycolide) microparticles.

PURPOSE: The objective of the reported work was to quantitatively establish gamma-irradiation dose effects on initial molecular weight distributions and in vitro degradation rates of a candidate erodible biopolymeric delivery system. METHODS: Poly(D,L-lactide-coglycolide) (PLGA) porous microparticles were prepared by a phase-separation technique using a 50:50 copolymer with 30,000 nominal molecular weight. The microparticles were subjected to 0, 1.5, 2.5, 3.5, 4.5, and 5.5 Mrad doses of gamma-irradiation and examined by size exclusion chromatography (SEC) to determine molecular weight distributions. The samples were subsequently incubated in vitro at 37 degrees C in pH 7.4 PBS and removed at timed intervals for gravimetric determinations of mass loss and SEC determinations of molecular weight reduction. RESULTS: Irradiation reduced initial molecular weight distributions as follows (Mn values shown parenthetically for irradiation doses): 0 Mrad (Mn = 25200 Da), 1.5 Mrad (18700 Da), 2.5 Mrad (17800 Da), 3.5 Mrad (13800 Da), 4.5 Mrad (12900 Da), 5.5 Mrad (11300 Da). In vitro degradation showed a lag period prior to zero-order loss of polymer mass. Onset times for mass loss decreased with increasing irradiation dose: 0 Mrad (onset = 3.4 weeks), 1.5 Mrad (2.0 w), 2.5 Mrad (1.5 w), 3.5 Mrad (1.3 w), 4.5 Mrad (1.0 w), 5.5 Mrad (0.8 w). The zero-order mass loss rate was 12%/week, independent of irradiation dose. Onset of erosion corresponded to Mn = 5200 Da, the point where the copolymer becomes appreciably soluble. CONCLUSIONS: The data demonstrated a substantial effect of gamma-irradiation on initial molecular weight distribution and onset of mass loss for PLGA, but no effect on rate of mass loss.

Electrochemical evaluation of the interaction between ascorbic acid and the cardiotonic drug RS-82856.

The solution phase interaction between ascorbic acid and the cardiotonic drug N-cyclohexyl-N-methyl-4(7-oxy 1,2,3,5-tetrahydroimidazol[2,1-b] quinazolin-2-one butyramide (RS-82856) was evaluated using a differential pulse voltammetric technique. Shifts in the peak potential of ascorbic acid to higher energy as well as decreases in peak current values were monitored as a function of RS-82856 concentration. The electrochemical data were obtained under conditions where both the drug and the ascorbic acid concentrations exhibited linear relationships with peak current values. The methodology was extended to the study of two other structurally related phosphodiesterase inhibitors cilostamide and anagrelide. The complexation of these drugs with ascorbic acid were also characterized by decreases in the diffusion currents of ascorbic acid as well as by anodic shifts in the peak potential. The significance of these observations may be related to the inhibition of cyclic nucleotide phosphodiesterase activity by both the drugs tested and the ascorbic acid.

Temperature and pH dependence of fluocinolone acetonide degradation in a topical cream formulation.

We investigated the degradation of fluocinolone acetonide (FA) incorporated into an oil-in-water cream base. The study examined the influence of temperature (23 to 80 degrees C) and cream pH (pH 2.3 to 6) on FA degradation rates. FA degradation followed pseudo-first-order kinetics and adhered to the Arrhenius expression over the entire temperature range investigated. At all temperatures, the pH strongly influenced the observed degradation rate constant (kobs) values, with rate minima observed near pH 4. The FA log(degradation rate)-pH profiles were consistent with a reaction mechanism requiring drug hydrolysis catalyzed by hydroxide and hydrogen ions. Taking into account both the temperature and the pH dependence of FA degradation permits calculating kobs values from the following equation: kobs = exp[22.5 - (17,200/RT)] + exp[38.7 - (22,200/RT)] x [H+] + exp[49.5 - (21,100/RT)] x [OH-] where the three bracketed terms represent Arrhenius expressions for neutral, acid-catalyzed, and base-catalyzed hydrolysis reactions. FA degradation in the cream base parallels the degradation of a related steroid (triamcinolone acetonide) in an aqueous alcohol solution. The equivalence between FA and triamcinolone acetonide kinetics in the different reaction media suggests that in the cream base, FA degradation is limited to an aqueous phase largely unperturbed by the presence of nonaqueous constituents that comprise the cream formulation.

Biotechnology and bone graft substitutes.

Trauma, disease, developmental deformities, and tumor resection frequently cause bone defects that seriously challenge the skills of orthopedic and maxillofacial surgeons. Currently, repairing osseous deficiencies involves various medical surgical techniques, including autogenous grafts, allografts, internal and external fixation devices, electrical stimulation, and alloplastic implants. The existing technology, though effective in many cases, still is beset with numerous difficulties and disadvantages. A critical need for improved treatment methods exists today. Biotechnology now provides access to new bone repair concepts via administration of protein growth and morphogenic factors. Implantable device and drug delivery system technologies also have advanced. The converging biopharmaceutical, device, and delivery technologies represent an opportunity to improve the quality of health care for individuals with orthopedic and maxillofacial deficiencies. This report reviews current concepts in fracture healing and bone repair and examines existing treatment modalities. It also addresses novel protein drugs that stimulate osseous regeneration and delivery systems for these drugs.