Ruminal boluses

Oral dosage forms available for administration to animals include oral solutions, liquids, suspensions, gels, pastes, capsules, tablets, ruminal boluses, powders and granules for addition to feed, soluble powders for... 

The modified-release ruminal bolus containing oxfendazole, designed for use in cattle in the body weight range of 200-400 kg, delivers pulse doses (1.25 g) at 3-week intervals over a period of 105 days. The bolus containing five tablets (Autoworm 5) releases the first dose at 21 days after administration whereas the bolus containing six tablets (Autoworm 6) releases the first dose on the day of administration. 

Controlled-release ruminal bolus Ivermectin Cattle P.O. 

Avermectin (Ivermectin) (Doramectin) (Abamectin) (Eprinomectin) Mites, lice, Horn fly. Warble-fly larvae Solution (pour on) Parenteral solution (S.C. injection) Controlled-release ruminal bolus (ivermectin)... 

Fig. 2.6 Technological design of (a) controlled-release ruminal bolus containing ivermectin for administration to cattle and (b) controlled-release ruminal capsule containing albendazole or ivermectin for administration to sheep. (Reproduced with permission from Klink et at. (1998).)...

Domestic sheep (Ovis aries) fed a low-zinc diet (2.2 mg Zn/kg DW diet) for 50 days, when compared to those fed a zinc-adequate diet (33 mg Zn/kg DW diet), excreted less zinc (<4 mg daily vs. 23 to 25), consumed less food (409 g daily vs. 898), and had lower plasma zinc concentrations (0.18 mg/L vs. 0.53 to 0.58) a reduction in plasma alkaline phosphatase activity and an increase in plasma zinc binding capacity were also noted (Khandaker and Telfer 1990). Sensitive indicators of zinc deficiency in lambs include significant reductions in plasma alkaline phosphatase activity and plasma zinc concentrations signs were clearly evident in lambs fed 10.8 mg Zn/kg DW diet for 50 to 180 days (Vergnes et al. 1990). A normal diet for lambs contains 124 to 130 mg Zn/kg DW ration vs. 33 for adults (Vergnes et al. 1990). One recommended treatment for zinc-deficient sheep is ruminal insertion of zinc-containing boluses every 40 days bolus zinc release is about 107 mg daily (Khandaker and Telfer 1990). 

When ruminating calves were given an intraruminal bolus containing 12 g morantel, the concentrations of morantel residues, after their conversion into 3-(3-methyl-2-thienyl)acrylic acid, in muscle, kidney, and liver, were 15, 40, and 150 ppb morantel equivalents, respectively, at 7 days after dosing. 

There are diverse formulations and delivery systems for macrocylic lactones in ruminants, including injectable, oral, sustained-release bolus and transdermal ("pour on") products. In Europe, it is popular clinical practice to administer injectable solutions of ivermectin intravenously (i.v.) to horses. This constitutes extra-label (unlicensed) use and there are no objective data to support the perceived improved efficacy following administration by this route. Specifically, in relation to hypobiotic cyathostome larvae, Klei et al (1993) reported no increase in efficacy when horses were administered 10 pg/kg, which is five times the recommended dose rate. 

When absorption takes place rapidly, which is usual for conventional dosage forms, fca > kd, but when absorption takes place slowly and ka < k(j the flip-flop phenomenon occurs, whereby the rate of absorption controls the rate of elimination of the drug. This situation applies not only to sustained-release oral dosage forms administered to dogs, but also to phenylbutazone and meclofe-namic acid in horses, salicylate administered as an aspirin bolus to cattle and oral suspensions of benzimidazole anthelmintics in ruminant species. 

The tetracycline derivatives are amphoteric substances that can form salts with both acids and bases. Hydrochloride is the most common salt form and is used in a variety of dosage forms, including medicated feeds, soluble powders, tablets and boluses, intrauterine infusions, intramammary infusions, and injections. Because the tetracyclines are relatively inexpensive, they tend to be used as first-line antimicrobials, especially in ruminants and pigs. Uses include... 

Bolus A solid mass of ingesta, also known as cud, which in ruminants is regurgitated for remastication during rumination. 

Cud A bolus of previously eaten feed that is regurgitated and rechewed by ruminants. 

Omasum The third compartment of the ruminant stomach consisting of a spherical organ containing various sized leaves that prevent undigested materials from leaving the rumen and entering the abomasum. It absorbs electrolytes from the bolus. 

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