Lec 13- exmples of reservoir systems

Question 1

Reservoir systems control of release rates

Ocusert

Answer 1

• Pilocarpine to the eye
  
  • Glaucoma
  • Pilo-20 20ug/h for 7 days
    
    • Delivers 3.4mg from 5mg
      *

Question 2

Ocusert structure

Answer 2

• Drug reservoir in the middle
• 2 release controlling membranes both above and below the reservoir
• Side supports- prevents drug release from the sides
  *

Question 3

Ocusert

Pilocarpine delivery to the eye

Answer 3

• Pilo 20 and 40
  
  • The amount of plasticiser in the Pilo 40 membrane is higher to increase drug diffusion (release)
  • Plasticiers make the formulation (device) more flexible which promotes drug diffusion through the membrane

Question 4

Reservoir systems- Control of release rates

Answer 4

• Mirena- Levonorgestrol-Intra-Uterine
  
  • Contraceptive, release through polydimethylsiloxane (PDS) membrane
  • 20 mcg/d for 5 years
    
    • Delivers 36.5mg from 52mg
• Progestasert- Progesterone-Intra-Uterine- same principle
• The deliver a fast smaller dose to the patient over a greater period of time to produce there therapeutic effect
• Patient doesn’t have to remember to take the pill daily, compliance and efficacy

Question 5

Nuvaring

Answer 5

• Contraceptive vaginal ring (organon) US 2002
• Inserted and left in place for 3 weeks
  
  • Release etonogestrel 0.12mg/d from 11.7mg
  • Ethynylestradiol 0.015mg/d from 2.7mg

Question 6

Reservoir systems

Estring

Answer 6

• Opaque ring of silicone elastomer with a whitish core containg the drug reservoir of 2mg
• DONT NEED TO REMEBER ALL EXAMPLES

Question 7

Norplant

(reservoir system) implantable device

Answer 7

• 6 flexible closed capsules each containing 38mg levonorgestrel
• Implanted subdermally, requires removal from site after release
• Release levonorgestrel over 5 years (Upto7 years )
• Diffusion through PDS membrane
• There was never any criticism of Norplant as an effective contraceptive
  
  • Voluntarily withdrawn due to dwindling use
  • Adverse publicity due to side-effects

Question 8

Reservoir systems

Implantable device (mixed system)

Implanon

Answer 8

• Flexible rod containing 60mg etonogestrel
• Implanted subdermally to give 60-70 mcg/d (wekks5-6) and 35-45 mcg/d after 1 year
• Release over 3 years
• Diffusion through an ethylvinylacetate co-polymer membrane with EVA copolymer matrix
• Requires removal from the site after release
• Mixed mechanism- matrix also contains EVA, so matrix and membrane restrict the release

Question 9

Implanon was discontinued and replaced by Nexplanon

Answer 9

• Implanon was discontinued and replace by Nexplanon a newer version of the implant designed to reduce the risk of insertion errors
• Nexplanon implants also contain a substance called barium, which allows them to be easily located using X-rays and CT-scans

Question 10

Reservoir systems

Vitrasert

Answer 10

• Surgical implant in the eye for treatment of CMV (Cytomegalovirus)
• Releases ganciclovir directly to the eye to increase local concentrations
• Active for about 7.5 months

Question 11

Ocular implants

Answer 11

• Chronic non-infectious uveitis affecting the posterior segment of the eye
• Fluocinolone acetonide (corticosteroid)

Question 12

Design of reservoir systems

Transiderm nitro

Answer 12

• GTN patch
• Covering membrane- prevents patch release on the top
• Micropourous membrane- control release of drug
• Adhesive- makes patch stick to the skin
• Stratum corneum is the main barrier and hurdle for transdermal delivery
• Once through the dermis, epidermis it reaches the capillaries and the systemic circulation- to which it can then exert its effect

Question 13

Control of drug delivery

Answer 13

• NB these are plasma profiles
• Normal skin there is a low plasma profile- provide harder path and entry for drugs
• Depending on the LogP and where you want the release will dictate where you are going to place the patch on the body

Question 14

HRT PATHCES

Answer 14

Question 15

MR SYSTEMS

Dual action device

Answer 15