Evaluation of the efficacy of transdermal delivery of chloroquine in male Sprague-Dawley rats infected with Plasmodium berghei: effects on blood glucose and renal electrolytes. Animals treated with a single topical application of the pectin-CHQ matrix patch presented blood glucose concentrations that were comparable to those of untreated, uninfected control animals.
Introduction/ Literature review
The Plasmodium life cycle and pathogenesis 2
- Role of hepcidin in anaemia 4
The erythrocyte stage of the Plasmodium life cycle is responsible for most of the pathology associated with malaria including fever and anemia. CHQ, the drug of choice in the present study exerts antimalarial activity by targeting this erythrocyte stage of the life cycle.
Management of malaria 5
- Control of malaria transmission 5
- Drug intervention for the management of malaria 6
- Artemisinin derivatives 6
- Quinine related drugs 7
Interestingly, treatment of uninfected animals with a single topical application of the pectin-CHQ matrix patch (56 mg) had no significant effect on 24-h voided urine volume, Na+, K+, and Cl- (Figure 11 ). After a simultaneous topical application of the pectin-CHQ matrix patch to uninfected and P.
Choroquine (CHQ) 8
- Mechanism of action 8
- CHQ absorption, metabolism and excretion 9
Adverse effects of CHQ or malaria 10
- Effects of malaria on blood glucose homeostasis 11
- Effects of CHQ on blood glucose 11
- Effects of malaria on renal function 12
- Effects of CHQ on renal function 12
Methods of drug delivery 14
- Transdermal drug delivery 14
However, oral administration of CHQ is associated with a number of disadvantages that have been previously described. Due to the accumulation of CHQ in the circulation when administered orally, a number of vital organs such as the heart, kidney and liver are adversely affected.
Physiology of the skin 15
The stratum corneum is physiologically responsible for the vital barrier function of the skin and does not allow drugs to spontaneously pass into the systemic circulation. The next section will discuss the composition of the stratum corneum and how it impedes drug transport into the systemic circulation for TDD systems. Literature evidence suggests that the barrier function of the skin is attributed to lamellar lipids synthesized in the granular layer.
The lipid domains of the stratum corneum are what pose a challenge for transdermal drug delivery as they hinder the spontaneous penetration of hydrophilic drugs. The transport of hydrophilic and charged molecules into the systemic circulation is hindered by the lipid-rich nature of the stratum corneum as well as the low water content (20%) (Mehta, 2004). Current evidence indicates that the thickness of the stratum corneum varies in different regions of the body and may affect drug transport.
The stratum corneum is thickest in the plantar and palmar regions and thinner in the postauricular, axillary, and scalp regions of the body (Mehta, 2004).
Penetration enhancers 16
- Sulphoxides 17
- Fatty acids 18
- Antioxidants 18
The rate at which drugs are transported across the stratum corneum is not only determined by the solubility of the drug, but is also directly proportional to the oil/water partition coefficient, drug concentration in the formulation vehicle as well as the surface area of the exposed skin. (Mehta, 2004). At high concentrations, DMSO can cause erythema and mottling of the stratum corneum and can denature proteins (Williams & Barry, 2012). The physiochemical structure of DMSO allows for the interaction of this molecule with the head groups of the lipid bilayer.
Like DMSO, DMF has been shown to cause irreversible changes in the stratum corneum at high concentrations (Williams & Barry, 2012). This permeability enhancer helps skin permeability by interacting with and modifying lipid domains of the stratum corneum. Transdermal drug delivery has many attractions, including increased patient compliance and avoidance of gastrointestinal disturbances and first-pass drug metabolism.
The stratum corneum is one of the limiting factors for the use of transdermal delivery as an alternative to other conventional drug administration routes.
Transdermal delivery polymers 19
- Chemistry of pectin 19
However, the single topical application of the pectin-CHQ matrix patch significantly (p<0.05) increased the mean body weight of P. Interestingly, the single topical application of the pectin-CHQ matrix patch significantly (p<0.05) increased blood glucose concentrations of P. Interestingly, after a single topical application of the pectin-CHQ patch, plasma insulin concentrations of P.
Interestingly, a single topical application of a pectin-CHQ patch had no significant effects on blood glucose levels in uninfected rats. Treatment of P.berghei-infected rats with a single topical application of a pectin-CHQ patch increased blood glucose compared to animals treated orally with CHQ. After a single topical application of a pectin-CHQ matrix patch, 24-hour urinary K+ excretion is P.
To distinguish between the effects of oral and transdermal CHQ treatment on MAP, uninfected and P.berghei -infected rats were treated with either oral CHQ or a single topical application of a pectin-CHQ matrix patch.
Basis of the study 21
Aims and objectives of the study 21
- Primary aims 21
- Secondary aims 21
Materials and methods 22
- Drugs and chemicals 22
- Animals 22
- Ethical consideration 22
- Experimental design 23
- Methods 23
- Preparation of pectin-CHQ matrix patches 23
- Determination of percentage incorporations 23
- Induction of malaria 24
- Effects of oral and transdermal treatments 24
- Parasitaemia monitoring 26
- Effects of CHQ on blood glucose and physic-metabolic parameters 26
- Effects of CHQ on mean arterial pressure (MAP) 26
- Terminal studies 27
- Laboratory analysis 28
- CHQ concentrations measurements 28
- Electrolyte measurements 28
- Hormonal measurements 29
- Data analysis 31
A volume of 2 mL of the final mixture was withdrawn for spectrophotometric analysis of CHQ (Ultraviolet Novaspec II spectrophotometer (Biochrom LTD, Cambridge, England). On the first day of the treatment period, CHQ pectin matrix patches were applied at 9:00 .treatment, mice were shaved on their dorsal region for application of the CHQ pectin matrix patch.
Plasma samples (50 µl) were added to the remaining anti-insulin wells, this was followed by the addition of the enzyme conjugate to the standard and plasma sample wells. A standard curve was constructed from absorbance values of known concentrations of standards using a spline regression curve. A standard curve was constructed from absorbance values of known concentrations of standards using the spline regression curve in the Graph Pad Instat program (version 5.00).
The corresponding AVP concentrations of the unknown samples were then extrapolated from the standard curve.
Results 32
General 32
CHQ incorporation in the pectin patch 32
Short-term studies 33
- Effects on parasitaemia
- Body weight, food and water intake 36
- Effects on blood glucose concentrations 38
- Effects on plasma insulin concentrations 41
- Renal function studies 43
- Effects on fluid, electrolyte handling and MAP 43
- Total urine volume, Na + , K + , and Cl - excreted during the treatment period 53
Body weight, food and water intake were monitored in uninfected and P. berghei -infected rats treated with either CHQ (30 mg, p.o.) twice daily or a single topical application of a pectin-CHQ matrix patch (56 mg) to differentiate between the effects of oral and transdermal CHQ treatment on these parameters. Blood glucose concentrations were monitored in separate groups of uninfected and P. berghei -infected rats treated with either CHQ (30 mg, p.o.) twice daily or a single topical application of a pectin-CHQ matrix patch (56 mg) to distinguished between the effects of oral and transdermal CHQ treatment. Oral administration of CHQ to uninfected animals significantly (p<0.05) decreased blood glucose concentration to mmol/L (Figure 5).
Interestingly, the one-time topical application of the pectin-CHQ patch did not alter the blood glucose concentrations of uninfected animals compared to untreated, uninfected animals (Figure 6). To elucidate the mechanisms responsible for the CHQ-induced hypoglycemia, blood was collected from separate groups of uninfected and P.berghei -infected rats treated twice daily with CHQ (30 mg, p.o) or a single topical application of the drug. pectin CHQ matrix patch (56 mg). Both oral CHQ administration and a single topical application of the pectin-CHQ patch significantly (p<0.05) increased plasma insulin concentrations of uninfected animals compared to the respective baseline values (Table 3).
The MAP and hematocrit value of untreated uninfected rats did not change during the 3-week study (Figure 9). However, oral administration of CHQ significantly (p<0.05) reduced both the MAP and hematocrit values of non-infected rats from day 8 to day 12 compared to the untreated non-infected control animals (Figure 9). Interestingly, a single topical application of the pectin-CHQ matrix patch had no significant effect on the MAP and hematocrit values of non-infected animals (Figure 13).
Laboratory analysis 55
- Plasma CHQ pharmacokinetics 55
- Effects of CHQ treatments on plasma AVP 56
To elucidate the possible mechanism responsible for the natriuretic effects of oral CHQ, plasma AVP concentrations were measured on samples collected from P. The samples were collected on day 1, day 4 of treatment, and day 21 of the period after treatment. Oral CHQ treatment significantly (p < 0.05) increased plasma AVP during the treatment period compared to baseline samples collected on day 7 from untreated P.
A single topical application of the pectin-CHQ matrix patch had no significant effect on plasma AVP concentrations compared to baseline.
Discussion 57
- General 57
- Effects of CHQ treatments on parasitaemia 58
- Blood glucose homeostasis 58
- Effects on renal function 61
- Renal effects of CHQ 61
- Effects of CHQ treatments on blood pressure 63
- CHQ Pharmacokinetics 63
This CHQ-induced natriuresis is believed to be mediated through increased plasma AVP concentrations (Musabayane et al., 1993). This suggests the ability of CHQ to interfere with the normal antidiuretic response to vasopressin by reducing cAMP formation (Musabayane et al., 2000). Kain and colleagues reported increased plasma K + in malaria patients infected with Plasmodium vivax treated with oral CHQ (Kain et al., 2001).
Indeed, we have previously reported a decrease in blood pressure and GFR after oral CHQ treatment (Musabayane et al., 1994. These findings are in agreement with previous reports showing rapid absorption of CHQ after oral CHQ administration of this drug (Gustafsson et al., 1983).In fact, we previously reported the ability of a pectic CHQ matrix patch to provide sustained release of CHQ (Musabayane et al., 2003).
The current study demonstrated the feasibility of using a pectin CHQ matrix patch for the topical application of CHQ in the treatment of malaria.
Conclusions 65
Shortfalls of the study 65
This study also established blood pressure-lowering effects of both the malaria parasites and oral CHQ treatment. No studies have been performed to elucidate the possible mechanisms responsible for these hypotensive effects of oral CHQ. Another limitation of the study is that CHQ concentration in tissues such as the kidney, liver, pancreas and heart was not assessed.
This is of interest since the oral CHQ-induced disturbances in blood glucose homeostasis and renal function are partly attributed to increased deposition of CHQ in these tissues.
Recommendations for future studies 66
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