1. Food Effects on Gastrointestinal Transit Properties of Amphotericin B Solid Lipid Nanoparticles
NASHIRU BILLA School of Pharmacy University of Nottingham, Malaysia Campus Malaysia

2. Amphotericin B (AmB) is a polyene antifungal agent highly effective in treating life-threatening systemic fungal infections
No oral AmB product currently available for use clinically
Research into oral AmB formulations as alternatives to the currently available yet costly intravenous formulations therefore relevant
Solid lipid nanoparticles (SLNs) have been shown to improve oral bioavailability of hydrophobic drugs (such as AmB) by enhancing lymphatic transport etc
No data on the regional preference to gastrointestinal (GI) absorption & Info on GI transit of AmB dosage forms lacking

3. Purpose To formulate AmB in SLNs intended for oral delivery
Study the GI absorption preference for AmB and GI transit properties of AmB SLN
To study the effect of food on the absorption of AmB in stomach, small intestine and colon

4. Methods
AmB, PAR and SSZ were similarly formulated in SLNs and physically characterised
Size
Surface charge
Morphology
Mobility propensity (in agarose gel)
In-vitro release (PBS – pH 7.4)
Animals
Male Sprague-Dawley rats (250±20 g) – 12/Ethical clearance
Fasted group allowed access to food 8 hr after dosing with the SLNs
Each animal was administered a single-dose oral gavage containing 10 mg/kg each of AmB, PAR and SSZ (freeze-dried SLNs or free drug) dispersed in deionised water
Blood samples withdrawn and analysed for the three drugs

5. GI transit parameters Gastric transit time (GTT) of AmB SLN
From plasma PAR absorption-time profiles
Assumption
% PAR absorbed is directly related to the % PAR SLNs emptied from the stomach into the duodenum.
Time for 10% PAR absorption (T10P) ≈ arrival of the SLNs at the small intestine.
Time for complete emptying of the SLNs (T90P) from the stomach was estimated using the time for 90% of PAR absorption in the small intestine
T90P ≈ GTT
Small intestinal transit time (SITT)
Plasma SP absorption-time profiles
SITT ≈ T10S - T10P
T10S = Time taken for 10% SP absorption in the caecum = caecal arrival of the SLNs

6. Caecal arrival time (CAT)
CAT = time taken for SLNs to arrive at the caecum
CAT has been estimated as the time for the initial detection of SP in the plasma using the indirect method of estimation
Due to the time lapse in SP production from SSZ released from SSZ SLNs reaching the caecum
CAT ≈ T10S
T10S serves as a better estimate for CAT of the SLNs than the initial SP detection in plasma
Initial SP detection may be mainly due to free SSZ released from the SLNs rather than SSZ released from the intact SSZ SLNs within the caecum
Colonic transit time (CTT)
The CTT was estimated as the time for 90% SP absorption (T90S)

7. RESULTS

8. Mean particle size and zeta potential
of the SLNs
SSZ
100 nm
AmB
PAR
SEM images of the SLNs
All three SLNs shared identical physical characteristics

9. In-vitro drug release in phosphate buffer (pH 7.4)
Agarose gel (a) before and (b, c) after voltage application

10. Key assumptions The SLNs exhibited similar physical characteristics
The assumption was therefore that all three SLNs would transit similarly within the GI tract
The slow in-vitro release from the AmB SLNs was favourable for the aim in improving AmB’s oral bioavailability

11. Plasma drug concentration of AmB
Effect of food on the absorption of PAR SLNs
CAT GE
Fasted rats

12. * p < 0.05 – statistical significance
CAT GE
Fasted rats GE
CAT
Fed rats
Rats
Tmax (hr)
Cmax (ng/mL)
AUC (ng.hr/mL)
Fasted
0.50±0.25
3616.3±68.4* ±
Fed
0.75±0.29
2383.3±747.9
±5712.2
* p < 0.05 – statistical significance

13. Pharmacokinetic parameters for AmB
Group
Dose (mg/kg)
Tmax (hr)
Cmax (ng/mL)
AUC (ng.hr/mL)
Fasted rats
AmB SLNs 10
8.00±0.00*
534.7±122.5*
7953.0±551.2*
Control
1.50±0.71
205.3±9.6#
4412.5±376.9
Fed rats
9.33±4.62**
323.2±44.0 **
7565.3± **
0.38±0.18
173.8±27.9
3343.0±209.3
* p < significantly different from AmB suspension in fasted rats
** p < significantly different from AmB suspension in fed rats
# p < significantly different compared with fed rats

14. Transit times of AmB SLNs in the GI tracts of the rats
Parameter 
Fasted rats
Fed rats
GTT (hr)
1.71±0.61
2.25±0.46
SITT (hr)
1.65±0.86
1.79±1.29
CAT (hr)
1.80±0.81
1.90±1.29
CTT (hr)
15.50±3.20*
24.60±2.60
* p < 0.05 – statistical significance
Estimated % absorption of AmB from SLNs in the stomach, small intestines and colon (n = 3)
Fasted rats
Fed rats
Stomach (%)
Small intestine (%)
Colon (%)
Stomach (%)
Colon++ (%)
Mean
2.8
44.1
53.1
3.2
37.2
59.6 SD
1.1
10.7
10.6
1.2
16.0
17.1

15. Key points GTT, SITT, CAT and CTT were longer in the fed rats
Only CTT was significantly longer in the fed state
Colon++ = Absorption processes in the colon + continued absorption process via lymph in the small intestines
Differences in %AmB absorption due to food in the respective GI regions were not statistically significant

16. Conclusions
The use of SLNs significantly enhanced the bioavailability of AmB in both fasted and fed rats
Food did not significantly alter the bioavailability of the AmB SLNs
Absorption process in SI appears to continue even after ceacal arrival
AmB oral formulations should probably be aimed for delayed SI transit