* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Phil Rowe Reader in pharmaceutical computing School of
Survey
Document related concepts
Discovery and development of proton pump inhibitors wikipedia , lookup
Compounding wikipedia , lookup
Psychopharmacology wikipedia , lookup
Drug design wikipedia , lookup
Pharmacognosy wikipedia , lookup
Tablet (pharmacy) wikipedia , lookup
Drug discovery wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Neuropharmacology wikipedia , lookup
Pharmaceutical industry wikipedia , lookup
Prescription costs wikipedia , lookup
Prescription drug prices in the United States wikipedia , lookup
Intravenous therapy wikipedia , lookup
Drug interaction wikipedia , lookup
Plateau principle wikipedia , lookup
Dydrogesterone wikipedia , lookup
Pharmacokinetics wikipedia , lookup
Transcript
Phil Rowe Reader in pharmaceutical computing School of Pharmacy & Chemistry All these presentations can be downloaded from: http://www.staff.livjm.ac.uk/phaprowe/ then follow 'Nurse prescribing' Lecture 2 Routes and patterns of drug administration Part 1 Routes of administration Routes to be covered: • Intravenous • Oral • Buccal & Rectal • Intramuscular • Subcutaneous • Topical Intravenous Advantages: • No absorption stage - immediate effect without delay • Guaranteed 100% bioavailability - no variation between patients Disadvantages: • Person administering dose needs careful training • Sterility essential • Possible extravasation Oral Advantages: • Simplicity Disadvantages: • Low and unpredictable bioavailability for some drugs • Rate of absorption - slow and unpredictable – Release from the tablet/capsule etc – Gastric emptying Gastric emptying Stomach Small intestine Drugs absorbed very slowly Drugs absorbed much more quickly Drug absorption from oral route Absorption may be delayed by: • Disintegration of dosage form (Tablet capsule etc) – Capsules (Soft gelatin) Few minutes – Capsules (Hard gelatin) Few minutes to an hour or more – Tablets Very variable Several hours for controlled release • Gastric emptying into intestine. – Liquid 50% in about 30 mins – Solids 50% in about 2 hours Buccal & Rectal Rectal may be useful if patient is vomiting. Rectal not terribly popular with British! Both may be useful in increasing bioavailability. Blood drainage from G.I.T. Mouth General circulation Stomach Small intestine Large intestine Rectum Liver General circulation Buccal & Rectal Both the buccal and the rectal route have the potential to increase bioavailability by allowing drugs to bye-pass the liver. Main advantage is that the dose that will reach the body is more predictable. Buccal route works well. e.g. Buccastem (Buccal prochlorperazine - antiemetic) delivers higher and more predictable dose than oral route. Rectal is less reliable. Effectiveness depends on the individual patient and the exact placing of the dose. Intramuscular Oil or water Drug Blood Rate of absorption of drug may be limited either by rate of release from injection vehicle or the ability of the blood to carry the drug away. Intramuscular • Oil based dosage form: Rate limiting step is release from vehicle. Slow (Many hours to a few weeks) but predictable. • Water based dosage form: Rate limiting step generally removal of released drug by blood flow. Quite quick, but very variable - exercise or rubbing the injection site will increase rate of dispersal into body. Subcutaneous Drug has to carried away from the injection site by blood or lymph. Both blood and lymph flows to the subcutaneous tissue are poor. Release therefore rather slow. If slow release is wanted, probably better to use a slow release formulation (Oil or plastic). Can be painful. Topical With topical application, intention is generally to achieve a local effect. However, in many cases, drug will be absorbed into the general circulation. Examples: • Inhaled steroids intended to act in the lungs, but are absorbed and can cause some adrenal suppression. • Beta-blockers in eye-drops reach measurable concentrations in blood. Part 2 Patterns of administration Patterns to be covered: • Single dose • Intravenous infusion • Multiple dose Single dose Rapid release - Useful for a "Quick hit". e.g. pain killers. Slow release - Useful where we want a prolonged steady exposure to the drug Intravenous infusion Css Steady state Intravenous infusion Rate of infusion Concentration at = steady state (Css) Clearance Use of a loading dose Immediately effective treatment Therapeutically effective range With loading dose No loading dose Multiple dose Accumulation with and without accumulation Much of of previous previousdose dosestill stillpresent present Previous dose fully eliminated Previous dosealmost almost fully eliminated Concentrations at Steady State Peak Average Trough Multiple dosing Bioavailability x Dose size Average = Conc Clearance x Dosage interval Divided doses 2 x 300 mg 3 x 200 mg 6 x 100 mg Divided doses Dose division should be great enough to ensure that peaks and troughs are not excessively high/low. But, always keep number of doses per day as low as possible to maximise compliance.