Heres the list people….
Methadone-oral 80-90%, halflife- 24-36 hours, rectal 76%
Ketobemiodone oral was 34% +/-10%, rectally 44% +/- 9%, half-life is 2.25- 2.45 hours
Meperidine rectal bioavailability is approximately 55%, 80% to 85% IM, elimination half-life 3.0 h
Buprenorphine highly protein bound 96%, sublingual bioavailability is approximately 30%, oral is 15-22%, 90-100% IM, elimination half-life is 12-44 hours
Hydromorphone– 5-8 times as potent as morphine, intranasal- 52.4%, Rectal administration 33% ,Oral-30-35%, (also reported as 50.7% +/- 29.8% oral; 33% +/- 22% rectal; 54.4% – 59.8% nasal)
Dihydrocodeine oral-20-21% halflife 4 hours
Heroin oral ~35% IV- 100% IM-85% Smoked (or vaporized?) 52-55% vaporized Semisynthetic derivative, Intranasal 44-61%
Fentanyl- Bioavailability 92% (transdermal), 50% (sublingual/ buccal (against cheek), Protein binding 80-85%, half-life 3-12 hours
Sufentanil intranasal bio- 78%,
Remifentanil Protein binding 70% (bound to plasma proteins) Half life 1-20 minutes
Alfentanil- IV ~100%, 92% protein binding, half life is 1.5-2 hours
Morphine ~32% oral/rectal, insuffulated- 15-20%, Chitosan(a linear polysaccharide that helps absorb drugs better) has been shown to increase nasal bioavailability of morphine from around 10-20% to over 60%, SC-60%, protein binding 30-40%, half-life is 2-3 hours
Oxycodone-oral 60-87% intranasal- widely varies 45-70%
Hydrocodone- oral bioavailability is not really known but it is around oxycodone bioavailability, ~70% of it is usually absorbed, half-life is 4-8 hours
Oxymorphone nasal bioavailabilty [43%] orals low 10-20%
Butorphanol -oral 5-17% due to high first pass metabolism
Tramadol- the absolute bioavailability of rectally admistered tramadol in the suppositories was 77.0%, Oral-68-72% (Increases with repeated dosing) Half life 5-7 hours
Codeine- following rectal or oral administration with a systemic availability of about 90%; in one study clearance varied 4-fold and systemic availability after oral dosage was between 50 and 84%
Diphenoxylate Protein binding 74-95% Half life 12-14 hours used for diarrhea, (does not appreciably cross the blood-brain barrier)
Pethidine(meperidine) Absorption Oral bioavailability is 50-60% in patients with normal hepatic function. IM 80-85%, Protein Binding 65-75%, Half Life 3-5 hours
Normeperidine is about half as potent as meperidine, but it has twice the CNS stimulation effects.
Pentazocine- Bioavailability ~20% orally, Half-life 2 to 3 hours

Opiate Antagonists
Naloxone oral- 2-4% (90% absorption but high first-pass metabolism), Half life 1-1.5 hours
Naltrexone Oral Bioavailability 5-40%, Protein binding 21%, Half life-4 hours (naltrexone),
and 13 hours (6-β-naltrexol) (metabolite)