Drug recovery following buccal absorption of propranolol

Prolonged Delivery of Apomorphine Through the Buccal Mucosa, Towards a Noninvasive Sustained Administration Method in Parkinson's Disease: In Vivo Investigations in Pigs

In the current work, prolonged systemic delivery of apomorphine via buccal mucosa was shown to be a promising treatment for Parkinson's disease as a substitute for clinically utilized subcutaneous infusions. Due to extensive 'first-pass' metabolism, apomorphine is administered parenterally to bypass liver metabolism. Drawbacks of parenteral administration cause low patient compliance and adherence to treatment. On the other hand, while also bypassing the liver, delivery through buccal mucosa has a superior safety profile, is less costly, lacks pain and discomfort, and possesses excellent accessibility, overall augmenting patient compliance. Current in vivo study in pigs showed: (1) steady plateau levels of apomorphine in plasma were obtained 30 min following administration and remained constant for 8 h until a delivery device was removed, (2) bioavailability of apomorphine was 55%-80% as opposed to <2% peroral and (3) simulation of the pharmacokinetic profile obtained in pigs predicted therapeutically relevant levels of apomorphine in human. Furthermore, antipyrine was incorporated as a permeation marker to enable mechanistic investigation of apomorphine release from the delivery device and its permeation through the buccal mucosa. In addition, limitations of an Ussing diffusion chamber as an ex vivo research tool were also discussed.

Prolonged oral transmucosal delivery of highly lipophilic drug cannabidiol

Delivery of drugs through oral mucosa enables bypass of the gastrointestinal tract and "first pass" metabolism in the liver and the gut. Thus, a higher and less variable bioavailability can be obtained. Mechanisms of this administration route for cannabidiol were investigated in the current research in pigs. Results show that cannabidiol has substantially low permeability rate over 8 h through oral mucosa and accumulates significantly within it. Furthermore, following the removal of the delivery device, residual prolongation of release from the oral mucosa into systemic blood circulation continues for several hours. This method of delivery enabled acquisition of clinically relevant plasma levels of cannabidiol. The absorption profile indicates that cannabidiol, as well as other lipophilic molecules, should be delivered through oral mucosa for systemic absorption from a device that conceals the drug and prevents its washout by the saliva flow and subsequent ingestion into gastrointestinal tract.

Bioavailability of propranolol after oral, sublingual, and intranasal administration

The bioavailability of propranolol was compared after oral, sublingual, and intranasal administration in eight healthy male volunteers. Relative to the bioavailability after intranasal (in) administration, which was previously shown to be nearly complete (F relin = 100%), the sublingual (sl) administration of a standard 10-mg tablet gave a bioavailability of F relsl = 63 ± 22%, while the oral (or) administration yielded only F relor = 25 ± 8%. The serum concentration-time curves of propranolol after sublingual administration resembled those of a sustained-release preparation. This sustained-release phenomenon after the sublingual route is reflected in the mean residence times (MRTs) of propranolol in the body (MRTor = 5.7 ± 1.3 hr, MRTsl - 6.4 ± 1.3 hr, MRTin = 4.6 ± 1.0 hr; mean ± SD; N = 8). MRTs after sublingual administration were significantly longer than after the oral and the intranasal doses (P < 0.05 and P < 0.002, respectively).

Clinical pharmacokinetics of buffered propranolol sublingual tablet (Promptol™)-application of a new "physiologically based" model to assess absorption and disposition

Sublingual administration of certain buffered propranolol may improve the rate and extent of absorption compared to oral administration. The main objectives of this study were to (1) compare the plasma propranolol concentrations (Cp-prop) following sublingual administration of a specially buffered formulation (Promptol™) to that following oral administration of Inderal(®) and (2) evaluate the utility of a special pharmacokinetic model in describing the Cp-prop following sublingual administration. Eighteen healthy volunteers received 10 mg sublingual Promptol™ or oral Inderal(®). Multiple Cp-prop were determined and their pharmacokinetics compared. Additional data following sublingual 40 mg Promptol™ or Inderal(®) were utilized for evaluation of a special advanced compartmental absorption and transit (ACAT) model. For model simulation, the physicochemical parameters were imported from AMET predictor, whereas the pharmacokinetic parameters were calculated and optimized by Gastroplus(®). Based on this model, the quantity of drug absorbed via buccal/sublingual mucosa was estimated. Cp-prop was higher at earlier times with 3-fold greater relative bioavailability following sublingual Promptol™ compared to that from oral Inderal(®). The special ACAT model provided excellent goodness of fit of Cp-prop-time curve and estimated a 56.6% increase in absorption rate from Promptol™ and higher initial Cp-prop compared to the regular formulation. The modified ACAT model provided a useful approach to describe sublingual absorption of propranolol and clearly demonstrated an improvement of absorption of Promptol™. The sublingual 10 mg Promptol™ achieved not only a similar systemic exposure as 30 mg oral Inderal(®) but an earlier effective Cp-prop which may be advantageous for certain clinical conditions.

Understanding the oral mucosal absorption and resulting clinical pharmacokinetics of asenapine

Absorption of drugs from the oral cavity into the mucosal tissues is typically a fast event. Dissolved drugs partition into the mucosal membranes and within minutes will reach equilibrium with drug in solution in the oral cavity. However, this does not always equate to rapid drug appearance in the systemic circulation. This has been attributed to slow partitioning out of the mucosal tissues and into the systemic circulation. Based on information from literature, physicochemical properties of asenapine, and clinical data, we conclude that for sublingually administered asenapine, the exposure is primarily a function of rapid partitioning into the mucosal membranes. This is followed by slow partitioning out of the mucosal tissues and into the systemic circulation, leading to a T (max) value of about 1 h. The bioavailability of asenapine at doses below the saturation solubility in the mouth does not change and is controlled primarily by mass transport equilibrium. At doses above the saturation solubility, the bioavailability becomes more dependent not only on the distribution equilibrium but also on contact time in the mouth because additional variables (e.g. dissolution rate of the drug) need to be accounted for. These explanations are consistent with oral cavity absorption models from the literature and can be used to accurately describe the clinical data for asenapine.

Buccal penetration enhancers--how do they really work?

Certain agents that increase drug delivery through the skin, including surfactants, bile salts, and fatty acids, have been shown to exert a similar effect on the buccal mucosa. These agents enhance skin permeability by interacting with and disrupting the ordered intercellular lipid lamellae within the keratinized stratum corneum, and it has been assumed that a similar mechanism of action occurs in the nonkeratinized buccal mucosa. However, the chemical and structural nature of the lipids present within the intercellular regions of the buccal mucosa is quite different to that found within the stratum corneum, and so extrapolation of results between these two tissues may be misleading. To assume that the mechanism of action of buccal penetration enhancers is based on the disruption of intercellular lipids may be erroneous, and may result in the inappropriate prediction that certain skin penetration enhancers will similarly enhance drug delivery through the buccal mucosa. The data available in the literature suggest that agents that enhance buccal penetration exert their effect by a mechanism other than by disruption of intercellular lipids. Rather, buccal penetration enhancement appears to result from agents being able to (a) increase the partitioning of drugs into the buccal epithelium, (b) extract (and not disrupt) intercellular lipids, (c) interact with epithelial protein domains, and/or (d) increase the retention of drugs at the buccal mucosal surface. The purpose of this review is to identify the major differences in the structural and chemical nature of the permeability barriers between the buccal mucosa and skin, to clarify the mechanisms of action of buccal penetration enhancers, and to identify the limitations of certain models that are used to assess the effect of buccal penetration enhancers.

Enhancing the buccal mucosal uptake and retention of triamcinolone acetonide

In this study, the buccal mucosal uptake and retention of triamcinolone acetonide (TAC) were assessed in the presence of the skin penetration enhancer, Azone (AZ). Porcine buccal mucosa was excised, mounted in modified Ussing chambers, and pretreated with ethanolic solutions of AZ. After 2 h, the rate of TAC disappearance from the donor chamber and TAC appearance in the receptor chamber was monitored, and the mucosal retention of TAC was determined at the completion of the experiment. The permeability and mucosal uptake of TAC was also determined using the TAC-containing proprietary product, Kenalog in Orabase (KO), in the presence and absence of AZ. Pretreatment of the buccal mucosa with AZ increased the TAC disappearance permeability coefficient from 4.78+/-0.31x10(-5) cm/s to 7.12+/-0.53x10(-5) cm/s. While the TAC appearance permeability coefficient was also enhanced 3.8-fold, a 4.4-fold increase in the tissue concentration of TAC was observed. Incorporation of AZ into KO did not result in an enhanced tissue concentration of TAC, however, when the tissue was pretreated with AZ, significantly higher amounts of TAC accumulated in the tissue. Pretreatment of the buccal mucosa with AZ results in increased tissue concentrations of TAC, which may be of clinical benefit in the treatment of oral mucosal inflammatory conditions.

Enhanced Buccal Mucosal Retention and Reduced Buccal Permeability of Estradiol in the Presence of Padimate O and Azone®: A Mechanistic Study

In previous experiments, it was suggested that the reduction in estradiol (E2) buccal permeability after pretreatment with some skin penetration enhancers was attributed to enhanced membrane storage. To verify this, further in vitro permeability experiments were performed and the kinetics of E2 buccal mucosal uptake and permeability was assessed. Porcine buccal mucosa was pretreated with the skin penetration enhancers octisalate, padimate O (PO), or Azone (AZ) and placed in modified Ussing chambers. The disappearance of E2 from the donor chamber and appearance of E2 in the receptor chamber was then monitored over 4 h. The final concentration of E2 associated with the buccal mucosa and donor chamber walls in the presence of each enhancer was also determined. The rate of E2 disappearance from the donor chamber was 3.1-fold greater than the rate of E2 appearance in the receptor chamber, indicating significant membrane storage of E2. Pretreatment with PO and AZ significantly increased the rate of E2 disappearance and reduced the rate of E2 appearance in the receptor chamber. The corresponding enhancement in E2 tissue concentration after PO and AZ pretreatment was 1.7- and 3-fold, respectively. However, PO and AZ also increased the amount of E2 adsorbed to the walls of the donor chamber, which contributed to the reduction in E2 flux through the buccal mucosa.

Modification of buccal drug delivery following pretreatment with skin penetration enhancers

The effect of the lipophilic skin penetration enhancers octisalate (OS), padimate O (PO), and Azone (AZ) on in vitro buccal permeability was assessed using caffeine (CAF), estradiol (E2), and triamcinolone acetonide (TAC) as model permeants. Buccal permeability was assessed in modified Ussing chambers, through both untreated porcine buccal mucosa and mucosa pretreated with an enhancer (5% w/v in 95% v/v ethanol) or ethanol alone. To ensure sink conditions were present, E2 permeability experiments were also performed with bovine serum albumin (BSA) 4% in the receptor solution. Mucosa-buffer partition studies were performed to determine the effect of enhancer pretreatment on the log mucosa-buffer partition coefficient (logK) of E2 and TAC. CAF permeability was only increased following pretreatment with ethanol 95%. E2 buccal transport was not altered following OS pretreatment, but was reduced by 26.3% with PO pretreatment and 67.6% with AZ pretreatment. Similar results were obtained with BSA 4% in the receptor solution. The logK of E2 was increased 1.4-fold and 2.2-fold in PO- and AZ-pretreated tissues, respectively, suggesting that the reduction in flux caused by PO and AZ may have been due to enhanced E2 tissue retention. The effect of OS and PO on TAC permeability was no different to that of ethanol. However, AZ enhanced TAC permeability 4.1-fold and this was accompanied by a 2.4-fold increase in the logK of TAC.

TR146 cells grown on filters as a model of human buccal epithelium: IV. Permeability of water, mannitol, testosterone and beta-adrenoceptor antagonists. Comparison to human, monkey and porcine buccal mucosa

The objective of the present study was to evaluate the TR146 cell culture model as an in vitro model of human buccal epithelium. For this purpose, the permeability of water, mannitol and testosterone across the TR146 cell culture model was compared to the permeability across human, monkey and porcine buccal mucosa. Further, the permeability rates of ten beta-adrenoceptor antagonists (acebutolol, alprenolol, atenolol, labetalol, metoprolol, oxprenolol, pindolol, propranolol, timolol and tertatolol) across the TR146 cell culture model and porcine buccal mucosa were related to their lipophilicity (logD(oct; 7.4)) and capacity factor (k') and to their polar water accessible surface area (PWASA). For water, mannitol, testosterone and some of the beta-adrenoceptor antagonists, the permeability enhancement across the TR146 cell culture model in the presence of sodium glycocholate (GC) was determined. The mannitol and testosterone permeability across the TR146 cell culture model could be related to the permeability across porcine and human buccal mucosa. The permeability of the beta-adrenoceptor antagonists across the TR146 cell culture model varied between 2.2 x 10(-6) cm/s (atenolol) and 165 x 10(-6) cm/s (metoprolol). For propranolol the cellular permeability value (P(c)) was lower than expected, probably due to accumulation in the TR146 cell layers. Limited correlation of permeability with k' was observed both for the TR146 cell culture model and the porcine buccal mucosa, although the porcine permeability values were approximately 100 times less than the values determined with the TR146 cell culture model. The permeability values were also found to decrease with increasing PWASA. The PWASA value seemed to be more predictable for permeability than k'. The presence of 12.5 mM GC increased the permeability only for the hydrophilic atenolol, which may help explain the mechanism for GC-induced enhancement. The present results indicate that the TR146 cell culture model can be used as an in vitro model for permeability studies and mechanistic studies of human buccal drug delivery of drugs with different lipophilicity.

Absorption kinetics of oral sotalol combined with cisapride and sublingual sotalol in healthy subjects

AIMS

To study the absorption kinetics of sotalol following administration of different formulations. A formulation which results in fast absorption might be useful in the episodic treatment of paroxysmal supraventricular tachycardia (SVT), atrial fibrillation (Afib) or atrial flutter (Afl).

METHODS

In an open randomized crossover study seven healthy male volunteers were given an intravenous infusion of 20 mg sotalol, for assessing the absolute bioavailability, an oral solution containing 80 mg sotalol, an oral solution containing both 80 mg sotalol and 20 mg cisapride and an 80 mg sotalol tablet, which was taken sublingually.

RESULTS

The addition of cisapride decreased the time at which maximum serum concentrations were reached (tmax) from 2.79 (1.85-4.34) h to 1.16 (0.68-2.30) h (P=0.009) [95% CI: -2.59, -0.55] and increased the absorption rate constant (ka) from 0.49 (0.31-0.69) h(-1) to 1.26 (0.52-5.61) h(-1) (P=0.017). The absolute bioavailability of sotalol was reduced by cisapride from 1.00+/-0.15 to 0.70+/-0.26 (P=0.006), while maximum serum concentrations of both oral solutions were not significantly different. Compared with the sublingually administered tablet with a median tmax of 2.12 (0.89-3.28) h, the sotalol/cisapride oral solution gave a smaller tmax (p=0.009) [95% CI: -1.64, -0.36]. The ka of the sotalol/cisapride solution was significantly (P=0.010) larger than the ka of 0.56 (0.33-0.75) h(-1) found after sublingual administration of the tablet.

CONCLUSIONS

The sotalol/cisapride oral solution might be suitable for the episodic treatment of SVT, Afib or Afl.

Dextromoramide pharmacokinetics following sublingual administration

The extent of absorption and other pharmacokinetic parameters of dextromoramide following sublingual administration were assessed in five patients receiving chronic opioid analgesia. The use of the standard 5 mg tablet formulation was associated with negligible absorption in two patients, a prolonged time to peak concentration in the other three and substantial variability in clearance. The study concluded that the standard tablet formulation cannot be recommended for sublingual use where reliable, rapid onset analgesia is required.

Salivary flow induction by buccal permucosal pilocarpine in anesthetized beagle dogs

We tested whether permucosal delivery of pilocarpine nitrate could be used to elicit significant salivary secretion. Pilocarpine (pKa 6.6 at 37 degrees C) was applied as solutions (pHs 5.6, 6.6, 7.6; 15 mg/mL) to the buccal mucosa (2.8 cm2) of 6 anesthetized dogs. Saliva was collected continuously from cannulated submandibular and parotid ducts and blood sampled during and after drug administration. Plasma pilocarpine levels were determined by reversed-phase HPLC. Absorption rates were determined by use of data from separate zero-order intravenous infusions to the same dogs. Pilocarpine was buccally absorbed at a constant rate of 72.9 +/- 38.5 micrograms/kg/h following its application at pH 7.6. At this pH of the drug solution, the time to appearance of pilocarpine in blood plasma was 0.31 +/- 0.08 h, and the time to appearance of salivary flow was 0.86 +/- 0.32 h. A threshold dose of 32.9 +/- 7.5 micrograms/kg was required to induce secretion with the pH 7.6 drug, the steady-state submandibular flow rate was 0.14 +/- 0.11 mL/min/gland pair. Salivary flow induction was symmetrical and reached levels as high as 0.35 mL/min/submandibular gland pair without apparent tachyphylaxis. Results at pHs 5.6, 6.6, and 7.6 were consistent with the hypothesis that pilocarpine is primarily absorbed as un-ionized drug. The data indicate that transmucosal delivery of pilocarpine, avoiding "first pass" hepatic loss, may hold promise for the treatment of xerostomia.

Drug delivery via the mucous membranes of the oral cavity

The delivery of drugs via the mucous membranes lining the oral cavity (i.e., sublingual and buccal), with consideration of both systemic delivery and local therapy, is reviewed in this paper. The structure and composition of the mucosae at different sites in the oral cavity, factors affecting mucosal permeability, penetration enhancement, selection of appropriate experimental systems for studying mucosal permeability, and formulation factors relevant to the design of systems for oral mucosal delivery are discussed. Sublingual delivery gives rapid absorption and good bioavailability for some small permeants, although this site is not well suited to sustained-delivery systems. The buccal mucosa, by comparison, is considerably less permeable, but is probably better suited to the development of sustained-delivery systems. For these reasons, the buccal mucosa may have potential for delivering some of the growing number of peptide drugs, particularly those of low molecular weight, high potency, and/or long biological half-life. Development of safe and effective penetration enhancers will further expand the utility of this route. Local delivery is a relatively poorly studied area; in general, it is governed by many of the same considerations that apply to systemic delivery.

The influence of changes in buccal potential difference on the buccal absorption of propranolol

A buccal potential difference (b.p.d.) exists across the mucous membrane of the mouth, which can be made less negative by contact with aspirin. The influence of changing the b.p.d. with aspirin on the buccal absorption of propranolol from a series of buffers of pH5-10 has been studied in eight volunteers. The study confirmed that the buccal absorption of propranolol was markedly pH dependent, but pretreatment of the buccal membrane with aspirin had no influence on the absorption of propranolol.

The use of buccal partitioning as a model of drug absorption interactions

Bioavailability describes both the rate and extent of drug absorption. The buccal absorption technique is a useful method for the examination of changed extent of drug absorption resulting from drug absorption interactions. The present work examined the usefulness of drug recovery profiles (after buccal absorption) in evaluating the rate of drug absorption. Recovery data, in the case of propranolol, did not change markedly after marked changes in the drug absorption rate, indicating that recovery profiles are a poor monitoring tool for changed absorption rates. The rate of drug absorption can be found using the buccal absorption method; however, this involves several different experiments on different days and, also, data must be found by measuring the drug in the absorption solution which also contains the interactant. The latter agent may interfere with drug assay procedures. The present work involved the model drug propranolol. Other drugs perhaps may behave differently.

The use of buccal partitioning as a model to examine the effects of aluminium hydroxide gel on the absorption of propranolol

1 A buccal partitioning model showed no absorption interaction between propranolol and aluminium hydroxide gel in three volunteer subjects. 2 The previously reported in vivo interaction is therefore not due to propranolol adsorption to, or complexation with the antacid but is more probably due to a decreased gastric emptying rate caused by the antacid. 2 Buccal partitioning has proved useful in the examination of the mechanism of the propranolol/aluminium hydroxide absorption interaction and may also be a suitable in vivo bioavailability screening model for other drugs which can be partitioned in the buccal membranes.

The effect of variations in urinary pH on the pharmacokinetics of diethylcarbamazine

1 The partitioning of diethylcarbamazine (DEC) between octan-1-ol and aqueous buffer was shown to be dependent upon the pH of the buffer. 2 Buccal absorption of DEC in five subjects was shown to increase with increasing pH. 3 In view of these findings, the disposition of DEC was investigated in the same five subjects following the oral administration of 50 mg DEC citrate on two occasions. 4 The elimination half-life (T1/2) of DEC and the area under the plasma concentration v time curve (AUC) were significantly increased when an alkaline urinary pH was maintained compared with the values of these parameters obtained on a second occasion when an acidic urinary pH was maintained. Renal clearance and total urinary excretion of DEC were significantly less at alkaline urinary pH than under acidic conditions. 5 The clinical significance of these observations is discussed both with respect to dose modification under conditions of changing urinary pH and the possibility of the manipulation of urinary pH in order to produce more effective dosage regimens.