L32-absorption:sublingulal, buccal and rectal drug delivery

what is the MEC

its the mininum effective concentration- the smallest concentration at which the drug is effective

what is the MTC

it is the minimum toxic concentration at which above the drug becomes toxic

what are the two ways drugs can be delivered to the systemic system via the mouth

• sublingual

• buccal

where is the buccal

underneath the cheeks and behind the lips

where is the sublingual

underneath the tongue

what is the main barrier in getting drugs through the buccal/sublingual into systemic circulation

• the epithelium

whata re the three main mucosal types

masticatory- involved in eating

lining-delivery of drugs

specialised lining like the tongue

describe the difference in thickness, permeability and residence time for buccal and sublingual

• buccal is more thicker than the sublingual route

• the sublingual route is the most permeable

• buccal has a better residence time than sublingual

what is the effect of saliva and mucus for drug absorption via the epithelia

• saliva is mainly made up of water + mucus, electrolytes and enzymes

• the mucus acts as a physical barrier to drug absorption

• saliva can aid and hinder absorption as it provides aqueous environment that’s needed for drugs but saliva wash out can occur (dosage form can be washed away )

describe the blood supply in the mouth

• there is good blood supply in the mouth and good blood flow

• this allows drugs to enter the systemic circulation avoiding hepatic first pass effect in the liver

what are some other factors that effect the success of delivering drugs via the mouth

• residence time- sustained delivery possible

• taste

• irritation

• compliance- talking, eating drinking

what are three types of dosage forms available for transmucosal delivery

• quick release

• controlled release- slow release over time

• pulsatile release-burst of delivery then slow release

list some advantages and disadvantages of using sublingual and buccal delivery methods

when is rectal drug administration best used

• unconscious patients

• children

• patients with nausea or vomiting

• patients with upper GI tract disease

• drugs with bad taste

• drugs that are heavily degraded by oral delivery

describe the anatomy of the rectum

• its the last 15-20cm of the colon

• normally empty

• relatively high surface area but there’s no villi to increase it - unlike small intestines

• around 3m of mucus which coats it

• neutral ph.

• one cell thick epithelium

describe the rectal absorption of drugs

• transcellular and paracellular absorption which depends on the size, lipophilicity and the ionisation of the drug through the simple epithelium

• the simple one cell thick epithelium means there’s rapid absorption across it

what are the main dosage forms for rectal administration of drugs

• suppositories

• capsules

• tablets

• ointments, creams and gels

• solutions emulsions and suspensions

describe the rectal blood supply

• it contains venous drainage which avoids the blood being transferred to the liver

• there’s a possible avoidance of hepatic first pass mostly avoided in the lower region and not higher as in the higher region there’s most cross over with hepatic portal vein

what are the advantages and disadvantages of administering a drug via the rectal route